Merge tag 'scmi-fixes-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into arm/fixes

ARM SCMI fixes for v5.4

Couple of fixes: one in scmi reset driver initialising missed scmi handle
and an other in scmi reset API implementation fixing the assignment of
reset state

* tag 'scmi-fixes-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  reset: reset-scmi: add missing handle initialisation
  firmware: arm_scmi: reset: fix reset_state assignment in scmi_domain_reset

Link: https://lore.kernel.org/r/20190918142139.GA4370@bogus
Signed-off-by: Olof Johansson <olof@lixom.net>

9 files changed, 788 insertions, 191 deletions

diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index c47d28d556b6..5f298f00a82e 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -2,5 +2,5 @@
 obj-y	= scmi-bus.o scmi-driver.o scmi-protocols.o
 scmi-bus-y = bus.o
 scmi-driver-y = driver.o
-scmi-protocols-y = base.o clock.o perf.o power.o sensors.o
+scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o
 obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o
diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c
index 204390297f4b..f804e8af6521 100644
--- a/drivers/firmware/arm_scmi/base.c
+++ b/drivers/firmware/arm_scmi/base.c
@@ -204,7 +204,7 @@ static int scmi_base_discover_agent_get(const struct scmi_handle *handle,
 	if (ret)
 		return ret;
 
-	*(__le32 *)t->tx.buf = cpu_to_le32(id);
+	put_unaligned_le32(id, t->tx.buf);
 
 	ret = scmi_do_xfer(handle, t);
 	if (!ret)
diff --git a/drivers/firmware/arm_scmi/clock.c b/drivers/firmware/arm_scmi/clock.c
index 0a194af92438..32526a793f3a 100644
--- a/drivers/firmware/arm_scmi/clock.c
+++ b/drivers/firmware/arm_scmi/clock.c
@@ -56,7 +56,7 @@ struct scmi_msg_resp_clock_describe_rates {
 struct scmi_clock_set_rate {
 	__le32 flags;
 #define CLOCK_SET_ASYNC		BIT(0)
-#define CLOCK_SET_DELAYED	BIT(1)
+#define CLOCK_SET_IGNORE_RESP	BIT(1)
 #define CLOCK_SET_ROUND_UP	BIT(2)
 #define CLOCK_SET_ROUND_AUTO	BIT(3)
 	__le32 id;
@@ -67,6 +67,7 @@ struct scmi_clock_set_rate {
 struct clock_info {
 	int num_clocks;
 	int max_async_req;
+	atomic_t cur_async_req;
 	struct scmi_clock_info *clk;
 };
 
@@ -106,7 +107,7 @@ static int scmi_clock_attributes_get(const struct scmi_handle *handle,
 	if (ret)
 		return ret;
 
-	*(__le32 *)t->tx.buf = cpu_to_le32(clk_id);
+	put_unaligned_le32(clk_id, t->tx.buf);
 	attr = t->rx.buf;
 
 	ret = scmi_do_xfer(handle, t);
@@ -203,39 +204,47 @@ scmi_clock_rate_get(const struct scmi_handle *handle, u32 clk_id, u64 *value)
 	if (ret)
 		return ret;
 
-	*(__le32 *)t->tx.buf = cpu_to_le32(clk_id);
+	put_unaligned_le32(clk_id, t->tx.buf);
 
 	ret = scmi_do_xfer(handle, t);
-	if (!ret) {
-		__le32 *pval = t->rx.buf;
-
-		*value = le32_to_cpu(*pval);
-		*value |= (u64)le32_to_cpu(*(pval + 1)) << 32;
-	}
+	if (!ret)
+		*value = get_unaligned_le64(t->rx.buf);
 
 	scmi_xfer_put(handle, t);
 	return ret;
 }
 
 static int scmi_clock_rate_set(const struct scmi_handle *handle, u32 clk_id,
-			       u32 config, u64 rate)
+			       u64 rate)
 {
 	int ret;
+	u32 flags = 0;
 	struct scmi_xfer *t;
 	struct scmi_clock_set_rate *cfg;
+	struct clock_info *ci = handle->clk_priv;
 
 	ret = scmi_xfer_get_init(handle, CLOCK_RATE_SET, SCMI_PROTOCOL_CLOCK,
 				 sizeof(*cfg), 0, &t);
 	if (ret)
 		return ret;
 
+	if (ci->max_async_req &&
+	    atomic_inc_return(&ci->cur_async_req) < ci->max_async_req)
+		flags |= CLOCK_SET_ASYNC;
+
 	cfg = t->tx.buf;
-	cfg->flags = cpu_to_le32(config);
+	cfg->flags = cpu_to_le32(flags);
 	cfg->id = cpu_to_le32(clk_id);
 	cfg->value_low = cpu_to_le32(rate & 0xffffffff);
 	cfg->value_high = cpu_to_le32(rate >> 32);
 
-	ret = scmi_do_xfer(handle, t);
+	if (flags & CLOCK_SET_ASYNC)
+		ret = scmi_do_xfer_with_response(handle, t);
+	else
+		ret = scmi_do_xfer(handle, t);
+
+	if (ci->max_async_req)
+		atomic_dec(&ci->cur_async_req);
 
 	scmi_xfer_put(handle, t);
 	return ret;
diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 44fd4f9404a9..5237c2ff79fe 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -15,6 +15,8 @@
 #include <linux/scmi_protocol.h>
 #include <linux/types.h>
 
+#include <asm/unaligned.h>
+
 #define PROTOCOL_REV_MINOR_MASK	GENMASK(15, 0)
 #define PROTOCOL_REV_MAJOR_MASK	GENMASK(31, 16)
 #define PROTOCOL_REV_MAJOR(x)	(u16)(FIELD_GET(PROTOCOL_REV_MAJOR_MASK, (x)))
@@ -48,11 +50,11 @@ struct scmi_msg_resp_prot_version {
 /**
  * struct scmi_msg_hdr - Message(Tx/Rx) header
  *
- * @id: The identifier of the command being sent
- * @protocol_id: The identifier of the protocol used to send @id command
- * @seq: The token to identify the message. when a message/command returns,
- *	the platform returns the whole message header unmodified including
- *	the token
+ * @id: The identifier of the message being sent
+ * @protocol_id: The identifier of the protocol used to send @id message
+ * @seq: The token to identify the message. When a message returns, the
+ *	platform returns the whole message header unmodified including the
+ *	token
  * @status: Status of the transfer once it's complete
  * @poll_completion: Indicate if the transfer needs to be polled for
  *	completion or interrupt mode is used
@@ -84,17 +86,21 @@ struct scmi_msg {
  * @rx: Receive message, the buffer should be pre-allocated to store
  *	message. If request-ACK protocol is used, we can reuse the same
  *	buffer for the rx path as we use for the tx path.
- * @done: completion event
+ * @done: command message transmit completion event
+ * @async: pointer to delayed response message received event completion
  */
 struct scmi_xfer {
 	struct scmi_msg_hdr hdr;
 	struct scmi_msg tx;
 	struct scmi_msg rx;
 	struct completion done;
+	struct completion *async_done;
 };
 
 void scmi_xfer_put(const struct scmi_handle *h, struct scmi_xfer *xfer);
 int scmi_do_xfer(const struct scmi_handle *h, struct scmi_xfer *xfer);
+int scmi_do_xfer_with_response(const struct scmi_handle *h,
+			       struct scmi_xfer *xfer);
 int scmi_xfer_get_init(const struct scmi_handle *h, u8 msg_id, u8 prot_id,
 		       size_t tx_size, size_t rx_size, struct scmi_xfer **p);
 int scmi_handle_put(const struct scmi_handle *handle);
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index b5bc4c7a8fab..3eb0382491ce 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -30,8 +30,14 @@
 #include "common.h"
 
 #define MSG_ID_MASK		GENMASK(7, 0)
+#define MSG_XTRACT_ID(hdr)	FIELD_GET(MSG_ID_MASK, (hdr))
 #define MSG_TYPE_MASK		GENMASK(9, 8)
+#define MSG_XTRACT_TYPE(hdr)	FIELD_GET(MSG_TYPE_MASK, (hdr))
+#define MSG_TYPE_COMMAND	0
+#define MSG_TYPE_DELAYED_RESP	2
+#define MSG_TYPE_NOTIFICATION	3
 #define MSG_PROTOCOL_ID_MASK	GENMASK(17, 10)
+#define MSG_XTRACT_PROT_ID(hdr)	FIELD_GET(MSG_PROTOCOL_ID_MASK, (hdr))
 #define MSG_TOKEN_ID_MASK	GENMASK(27, 18)
 #define MSG_XTRACT_TOKEN(hdr)	FIELD_GET(MSG_TOKEN_ID_MASK, (hdr))
 #define MSG_TOKEN_MAX		(MSG_XTRACT_TOKEN(MSG_TOKEN_ID_MASK) + 1)
@@ -86,7 +92,7 @@ struct scmi_desc {
 };
 
 /**
- * struct scmi_chan_info - Structure representing a SCMI channel informfation
+ * struct scmi_chan_info - Structure representing a SCMI channel information
  *
  * @cl: Mailbox Client
  * @chan: Transmit/Receive mailbox channel
@@ -111,8 +117,9 @@ struct scmi_chan_info {
  * @handle: Instance of SCMI handle to send to clients
  * @version: SCMI revision information containing protocol version,
  *	implementation version and (sub-)vendor identification.
- * @minfo: Message info
- * @tx_idr: IDR object to map protocol id to channel info pointer
+ * @tx_minfo: Universal Transmit Message management info
+ * @tx_idr: IDR object to map protocol id to Tx channel info pointer
+ * @rx_idr: IDR object to map protocol id to Rx channel info pointer
  * @protocols_imp: List of protocols implemented, currently maximum of
  *	MAX_PROTOCOLS_IMP elements allocated by the base protocol
  * @node: List head
@@ -123,8 +130,9 @@ struct scmi_info {
 	const struct scmi_desc *desc;
 	struct scmi_revision_info version;
 	struct scmi_handle handle;
-	struct scmi_xfers_info minfo;
+	struct scmi_xfers_info tx_minfo;
 	struct idr tx_idr;
+	struct idr rx_idr;
 	u8 *protocols_imp;
 	struct list_head node;
 	int users;
@@ -182,7 +190,7 @@ static inline int scmi_to_linux_errno(int errno)
 static inline void scmi_dump_header_dbg(struct device *dev,
 					struct scmi_msg_hdr *hdr)
 {
-	dev_dbg(dev, "Command ID: %x Sequence ID: %x Protocol: %x\n",
+	dev_dbg(dev, "Message ID: %x Sequence ID: %x Protocol: %x\n",
 		hdr->id, hdr->seq, hdr->protocol_id);
 }
 
@@ -190,7 +198,7 @@ static void scmi_fetch_response(struct scmi_xfer *xfer,
 				struct scmi_shared_mem __iomem *mem)
 {
 	xfer->hdr.status = ioread32(mem->msg_payload);
-	/* Skip the length of header and statues in payload area i.e 8 bytes*/
+	/* Skip the length of header and status in payload area i.e 8 bytes */
 	xfer->rx.len = min_t(size_t, xfer->rx.len, ioread32(&mem->length) - 8);
 
 	/* Take a copy to the rx buffer.. */
@@ -198,56 +206,12 @@ static void scmi_fetch_response(struct scmi_xfer *xfer,
 }
 
 /**
- * scmi_rx_callback() - mailbox client callback for receive messages
- *
- * @cl: client pointer
- * @m: mailbox message
- *
- * Processes one received message to appropriate transfer information and
- * signals completion of the transfer.
- *
- * NOTE: This function will be invoked in IRQ context, hence should be
- * as optimal as possible.
- */
-static void scmi_rx_callback(struct mbox_client *cl, void *m)
-{
-	u16 xfer_id;
-	struct scmi_xfer *xfer;
-	struct scmi_chan_info *cinfo = client_to_scmi_chan_info(cl);
-	struct device *dev = cinfo->dev;
-	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
-	struct scmi_xfers_info *minfo = &info->minfo;
-	struct scmi_shared_mem __iomem *mem = cinfo->payload;
-
-	xfer_id = MSG_XTRACT_TOKEN(ioread32(&mem->msg_header));
-
-	/* Are we even expecting this? */
-	if (!test_bit(xfer_id, minfo->xfer_alloc_table)) {
-		dev_err(dev, "message for %d is not expected!\n", xfer_id);
-		return;
-	}
-
-	xfer = &minfo->xfer_block[xfer_id];
-
-	scmi_dump_header_dbg(dev, &xfer->hdr);
-	/* Is the message of valid length? */
-	if (xfer->rx.len > info->desc->max_msg_size) {
-		dev_err(dev, "unable to handle %zu xfer(max %d)\n",
-			xfer->rx.len, info->desc->max_msg_size);
-		return;
-	}
-
-	scmi_fetch_response(xfer, mem);
-	complete(&xfer->done);
-}
-
-/**
  * pack_scmi_header() - packs and returns 32-bit header
  *
  * @hdr: pointer to header containing all the information on message id,
  *	protocol id and sequence id.
  *
- * Return: 32-bit packed command header to be sent to the platform.
+ * Return: 32-bit packed message header to be sent to the platform.
  */
 static inline u32 pack_scmi_header(struct scmi_msg_hdr *hdr)
 {
@@ -257,6 +221,18 @@ static inline u32 pack_scmi_header(struct scmi_msg_hdr *hdr)
 }
 
 /**
+ * unpack_scmi_header() - unpacks and records message and protocol id
+ *
+ * @msg_hdr: 32-bit packed message header sent from the platform
+ * @hdr: pointer to header to fetch message and protocol id.
+ */
+static inline void unpack_scmi_header(u32 msg_hdr, struct scmi_msg_hdr *hdr)
+{
+	hdr->id = MSG_XTRACT_ID(msg_hdr);
+	hdr->protocol_id = MSG_XTRACT_PROT_ID(msg_hdr);
+}
+
+/**
  * scmi_tx_prepare() - mailbox client callback to prepare for the transfer
  *
  * @cl: client pointer
@@ -271,6 +247,14 @@ static void scmi_tx_prepare(struct mbox_client *cl, void *m)
 	struct scmi_chan_info *cinfo = client_to_scmi_chan_info(cl);
 	struct scmi_shared_mem __iomem *mem = cinfo->payload;
 
+	/*
+	 * Ideally channel must be free by now unless OS timeout last
+	 * request and platform continued to process the same, wait
+	 * until it releases the shared memory, otherwise we may endup
+	 * overwriting its response with new message payload or vice-versa
+	 */
+	spin_until_cond(ioread32(&mem->channel_status) &
+			SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
 	/* Mark channel busy + clear error */
 	iowrite32(0x0, &mem->channel_status);
 	iowrite32(t->hdr.poll_completion ? 0 : SCMI_SHMEM_FLAG_INTR_ENABLED,
@@ -285,8 +269,9 @@ static void scmi_tx_prepare(struct mbox_client *cl, void *m)
  * scmi_xfer_get() - Allocate one message
  *
  * @handle: Pointer to SCMI entity handle
+ * @minfo: Pointer to Tx/Rx Message management info based on channel type
  *
- * Helper function which is used by various command functions that are
+ * Helper function which is used by various message functions that are
  * exposed to clients of this driver for allocating a message traffic event.
  *
  * This function can sleep depending on pending requests already in the system
@@ -295,13 +280,13 @@ static void scmi_tx_prepare(struct mbox_client *cl, void *m)
  *
  * Return: 0 if all went fine, else corresponding error.
  */
-static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle)
+static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle,
+				       struct scmi_xfers_info *minfo)
 {
 	u16 xfer_id;
 	struct scmi_xfer *xfer;
 	unsigned long flags, bit_pos;
 	struct scmi_info *info = handle_to_scmi_info(handle);
-	struct scmi_xfers_info *minfo = &info->minfo;
 
 	/* Keep the locked section as small as possible */
 	spin_lock_irqsave(&minfo->xfer_lock, flags);
@@ -324,18 +309,17 @@ static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle)
 }
 
 /**
- * scmi_xfer_put() - Release a message
+ * __scmi_xfer_put() - Release a message
  *
- * @handle: Pointer to SCMI entity handle
+ * @minfo: Pointer to Tx/Rx Message management info based on channel type
  * @xfer: message that was reserved by scmi_xfer_get
  *
  * This holds a spinlock to maintain integrity of internal data structures.
  */
-void scmi_xfer_put(const struct scmi_handle *handle, struct scmi_xfer *xfer)
+static void
+__scmi_xfer_put(struct scmi_xfers_info *minfo, struct scmi_xfer *xfer)
 {
 	unsigned long flags;
-	struct scmi_info *info = handle_to_scmi_info(handle);
-	struct scmi_xfers_info *minfo = &info->minfo;
 
 	/*
 	 * Keep the locked section as small as possible
@@ -347,6 +331,68 @@ void scmi_xfer_put(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 	spin_unlock_irqrestore(&minfo->xfer_lock, flags);
 }
 
+/**
+ * scmi_rx_callback() - mailbox client callback for receive messages
+ *
+ * @cl: client pointer
+ * @m: mailbox message
+ *
+ * Processes one received message to appropriate transfer information and
+ * signals completion of the transfer.
+ *
+ * NOTE: This function will be invoked in IRQ context, hence should be
+ * as optimal as possible.
+ */
+static void scmi_rx_callback(struct mbox_client *cl, void *m)
+{
+	u8 msg_type;
+	u32 msg_hdr;
+	u16 xfer_id;
+	struct scmi_xfer *xfer;
+	struct scmi_chan_info *cinfo = client_to_scmi_chan_info(cl);
+	struct device *dev = cinfo->dev;
+	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
+	struct scmi_xfers_info *minfo = &info->tx_minfo;
+	struct scmi_shared_mem __iomem *mem = cinfo->payload;
+
+	msg_hdr = ioread32(&mem->msg_header);
+	msg_type = MSG_XTRACT_TYPE(msg_hdr);
+	xfer_id = MSG_XTRACT_TOKEN(msg_hdr);
+
+	if (msg_type == MSG_TYPE_NOTIFICATION)
+		return; /* Notifications not yet supported */
+
+	/* Are we even expecting this? */
+	if (!test_bit(xfer_id, minfo->xfer_alloc_table)) {
+		dev_err(dev, "message for %d is not expected!\n", xfer_id);
+		return;
+	}
+
+	xfer = &minfo->xfer_block[xfer_id];
+
+	scmi_dump_header_dbg(dev, &xfer->hdr);
+
+	scmi_fetch_response(xfer, mem);
+
+	if (msg_type == MSG_TYPE_DELAYED_RESP)
+		complete(xfer->async_done);
+	else
+		complete(&xfer->done);
+}
+
+/**
+ * scmi_xfer_put() - Release a transmit message
+ *
+ * @handle: Pointer to SCMI entity handle
+ * @xfer: message that was reserved by scmi_xfer_get
+ */
+void scmi_xfer_put(const struct scmi_handle *handle, struct scmi_xfer *xfer)
+{
+	struct scmi_info *info = handle_to_scmi_info(handle);
+
+	__scmi_xfer_put(&info->tx_minfo, xfer);
+}
+
 static bool
 scmi_xfer_poll_done(const struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
 {
@@ -435,8 +481,36 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 	return ret;
 }
 
+#define SCMI_MAX_RESPONSE_TIMEOUT	(2 * MSEC_PER_SEC)
+
+/**
+ * scmi_do_xfer_with_response() - Do one transfer and wait until the delayed
+ *	response is received
+ *
+ * @handle: Pointer to SCMI entity handle
+ * @xfer: Transfer to initiate and wait for response
+ *
+ * Return: -ETIMEDOUT in case of no delayed response, if transmit error,
+ *	return corresponding error, else if all goes well, return 0.
+ */
+int scmi_do_xfer_with_response(const struct scmi_handle *handle,
+			       struct scmi_xfer *xfer)
+{
+	int ret, timeout = msecs_to_jiffies(SCMI_MAX_RESPONSE_TIMEOUT);
+	DECLARE_COMPLETION_ONSTACK(async_response);
+
+	xfer->async_done = &async_response;
+
+	ret = scmi_do_xfer(handle, xfer);
+	if (!ret && !wait_for_completion_timeout(xfer->async_done, timeout))
+		ret = -ETIMEDOUT;
+
+	xfer->async_done = NULL;
+	return ret;
+}
+
 /**
- * scmi_xfer_get_init() - Allocate and initialise one message
+ * scmi_xfer_get_init() - Allocate and initialise one message for transmit
  *
  * @handle: Pointer to SCMI entity handle
  * @msg_id: Message identifier
@@ -457,6 +531,7 @@ int scmi_xfer_get_init(const struct scmi_handle *handle, u8 msg_id, u8 prot_id,
 	int ret;
 	struct scmi_xfer *xfer;
 	struct scmi_info *info = handle_to_scmi_info(handle);
+	struct scmi_xfers_info *minfo = &info->tx_minfo;
 	struct device *dev = info->dev;
 
 	/* Ensure we have sane transfer sizes */
@@ -464,7 +539,7 @@ int scmi_xfer_get_init(const struct scmi_handle *handle, u8 msg_id, u8 prot_id,
 	    tx_size > info->desc->max_msg_size)
 		return -ERANGE;
 
-	xfer = scmi_xfer_get(handle);
+	xfer = scmi_xfer_get(handle, minfo);
 	if (IS_ERR(xfer)) {
 		ret = PTR_ERR(xfer);
 		dev_err(dev, "failed to get free message slot(%d)\n", ret);
@@ -597,27 +672,13 @@ int scmi_handle_put(const struct scmi_handle *handle)
 	return 0;
 }
 
-static const struct scmi_desc scmi_generic_desc = {
-	.max_rx_timeout_ms = 30,	/* We may increase this if required */
-	.max_msg = 20,		/* Limited by MBOX_TX_QUEUE_LEN */
-	.max_msg_size = 128,
-};
-
-/* Each compatible listed below must have descriptor associated with it */
-static const struct of_device_id scmi_of_match[] = {
-	{ .compatible = "arm,scmi", .data = &scmi_generic_desc },
-	{ /* Sentinel */ },
-};
-
-MODULE_DEVICE_TABLE(of, scmi_of_match);
-
 static int scmi_xfer_info_init(struct scmi_info *sinfo)
 {
 	int i;
 	struct scmi_xfer *xfer;
 	struct device *dev = sinfo->dev;
 	const struct scmi_desc *desc = sinfo->desc;
-	struct scmi_xfers_info *info = &sinfo->minfo;
+	struct scmi_xfers_info *info = &sinfo->tx_minfo;
 
 	/* Pre-allocated messages, no more than what hdr.seq can support */
 	if (WARN_ON(desc->max_msg >= MSG_TOKEN_MAX)) {
@@ -652,61 +713,32 @@ static int scmi_xfer_info_init(struct scmi_info *sinfo)
 	return 0;
 }
 
-static int scmi_mailbox_check(struct device_node *np)
+static int scmi_mailbox_check(struct device_node *np, int idx)
 {
-	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells", 0, NULL);
+	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells",
+					  idx, NULL);
 }
 
-static int scmi_mbox_free_channel(int id, void *p, void *data)
+static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
+				int prot_id, bool tx)
 {
-	struct scmi_chan_info *cinfo = p;
-	struct idr *idr = data;
-
-	if (!IS_ERR_OR_NULL(cinfo->chan)) {
-		mbox_free_channel(cinfo->chan);
-		cinfo->chan = NULL;
-	}
-
-	idr_remove(idr, id);
-
-	return 0;
-}
-
-static int scmi_remove(struct platform_device *pdev)
-{
-	int ret = 0;
-	struct scmi_info *info = platform_get_drvdata(pdev);
-	struct idr *idr = &info->tx_idr;
-
-	mutex_lock(&scmi_list_mutex);
-	if (info->users)
-		ret = -EBUSY;
-	else
-		list_del(&info->node);
-	mutex_unlock(&scmi_list_mutex);
-
-	if (ret)
-		return ret;
-
-	/* Safe to free channels since no more users */
-	ret = idr_for_each(idr, scmi_mbox_free_channel, idr);
-	idr_destroy(&info->tx_idr);
-
-	return ret;
-}
-
-static inline int
-scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev, int prot_id)
-{
-	int ret;
+	int ret, idx;
 	struct resource res;
 	resource_size_t size;
 	struct device_node *shmem, *np = dev->of_node;
 	struct scmi_chan_info *cinfo;
 	struct mbox_client *cl;
+	struct idr *idr;
+	const char *desc = tx ? "Tx" : "Rx";
 
-	if (scmi_mailbox_check(np)) {
-		cinfo = idr_find(&info->tx_idr, SCMI_PROTOCOL_BASE);
+	/* Transmit channel is first entry i.e. index 0 */
+	idx = tx ? 0 : 1;
+	idr = tx ? &info->tx_idr : &info->rx_idr;
+
+	if (scmi_mailbox_check(np, idx)) {
+		cinfo = idr_find(idr, SCMI_PROTOCOL_BASE);
+		if (unlikely(!cinfo)) /* Possible only if platform has no Rx */
+			return -EINVAL;
 		goto idr_alloc;
 	}
 
@@ -719,36 +751,36 @@ scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev, int prot_id)
 	cl = &cinfo->cl;
 	cl->dev = dev;
 	cl->rx_callback = scmi_rx_callback;
-	cl->tx_prepare = scmi_tx_prepare;
+	cl->tx_prepare = tx ? scmi_tx_prepare : NULL;
 	cl->tx_block = false;
-	cl->knows_txdone = true;
+	cl->knows_txdone = tx;
 
-	shmem = of_parse_phandle(np, "shmem", 0);
+	shmem = of_parse_phandle(np, "shmem", idx);
 	ret = of_address_to_resource(shmem, 0, &res);
 	of_node_put(shmem);
 	if (ret) {
-		dev_err(dev, "failed to get SCMI Tx payload mem resource\n");
+		dev_err(dev, "failed to get SCMI %s payload memory\n", desc);
 		return ret;
 	}
 
 	size = resource_size(&res);
 	cinfo->payload = devm_ioremap(info->dev, res.start, size);
 	if (!cinfo->payload) {
-		dev_err(dev, "failed to ioremap SCMI Tx payload\n");
+		dev_err(dev, "failed to ioremap SCMI %s payload\n", desc);
 		return -EADDRNOTAVAIL;
 	}
 
-	/* Transmit channel is first entry i.e. index 0 */
-	cinfo->chan = mbox_request_channel(cl, 0);
+	cinfo->chan = mbox_request_channel(cl, idx);
 	if (IS_ERR(cinfo->chan)) {
 		ret = PTR_ERR(cinfo->chan);
 		if (ret != -EPROBE_DEFER)
-			dev_err(dev, "failed to request SCMI Tx mailbox\n");
+			dev_err(dev, "failed to request SCMI %s mailbox\n",
+				desc);
 		return ret;
 	}
 
 idr_alloc:
-	ret = idr_alloc(&info->tx_idr, cinfo, prot_id, prot_id + 1, GFP_KERNEL);
+	ret = idr_alloc(idr, cinfo, prot_id, prot_id + 1, GFP_KERNEL);
 	if (ret != prot_id) {
 		dev_err(dev, "unable to allocate SCMI idr slot err %d\n", ret);
 		return ret;
@@ -758,6 +790,17 @@ idr_alloc:
 	return 0;
 }
 
+static inline int
+scmi_mbox_txrx_setup(struct scmi_info *info, struct device *dev, int prot_id)
+{
+	int ret = scmi_mbox_chan_setup(info, dev, prot_id, true);
+
+	if (!ret) /* Rx is optional, hence no error check */
+		scmi_mbox_chan_setup(info, dev, prot_id, false);
+
+	return ret;
+}
+
 static inline void
 scmi_create_protocol_device(struct device_node *np, struct scmi_info *info,
 			    int prot_id)
@@ -771,7 +814,7 @@ scmi_create_protocol_device(struct device_node *np, struct scmi_info *info,
 		return;
 	}
 
-	if (scmi_mbox_chan_setup(info, &sdev->dev, prot_id)) {
+	if (scmi_mbox_txrx_setup(info, &sdev->dev, prot_id)) {
 		dev_err(&sdev->dev, "failed to setup transport\n");
 		scmi_device_destroy(sdev);
 		return;
@@ -791,7 +834,7 @@ static int scmi_probe(struct platform_device *pdev)
 	struct device_node *child, *np = dev->of_node;
 
 	/* Only mailbox method supported, check for the presence of one */
-	if (scmi_mailbox_check(np)) {
+	if (scmi_mailbox_check(np, 0)) {
 		dev_err(dev, "no mailbox found in %pOF\n", np);
 		return -EINVAL;
 	}
@@ -814,12 +857,13 @@ static int scmi_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, info);
 	idr_init(&info->tx_idr);
+	idr_init(&info->rx_idr);
 
 	handle = &info->handle;
 	handle->dev = info->dev;
 	handle->version = &info->version;
 
-	ret = scmi_mbox_chan_setup(info, dev, SCMI_PROTOCOL_BASE);
+	ret = scmi_mbox_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
 	if (ret)
 		return ret;
 
@@ -854,6 +898,62 @@ static int scmi_probe(struct platform_device *pdev)
 	return 0;
 }
 
+static int scmi_mbox_free_channel(int id, void *p, void *data)
+{
+	struct scmi_chan_info *cinfo = p;
+	struct idr *idr = data;
+
+	if (!IS_ERR_OR_NULL(cinfo->chan)) {
+		mbox_free_channel(cinfo->chan);
+		cinfo->chan = NULL;
+	}
+
+	idr_remove(idr, id);
+
+	return 0;
+}
+
+static int scmi_remove(struct platform_device *pdev)
+{
+	int ret = 0;
+	struct scmi_info *info = platform_get_drvdata(pdev);
+	struct idr *idr = &info->tx_idr;
+
+	mutex_lock(&scmi_list_mutex);
+	if (info->users)
+		ret = -EBUSY;
+	else
+		list_del(&info->node);
+	mutex_unlock(&scmi_list_mutex);
+
+	if (ret)
+		return ret;
+
+	/* Safe to free channels since no more users */
+	ret = idr_for_each(idr, scmi_mbox_free_channel, idr);
+	idr_destroy(&info->tx_idr);
+
+	idr = &info->rx_idr;
+	ret = idr_for_each(idr, scmi_mbox_free_channel, idr);
+	idr_destroy(&info->rx_idr);
+
+	return ret;
+}
+
+static const struct scmi_desc scmi_generic_desc = {
+	.max_rx_timeout_ms = 30,	/* We may increase this if required */
+	.max_msg = 20,		/* Limited by MBOX_TX_QUEUE_LEN */
+	.max_msg_size = 128,
+};
+
+/* Each compatible listed below must have descriptor associated with it */
+static const struct of_device_id scmi_of_match[] = {
+	{ .compatible = "arm,scmi", .data = &scmi_generic_desc },
+	{ /* Sentinel */ },
+};
+
+MODULE_DEVICE_TABLE(of, scmi_of_match);
+
 static struct platform_driver scmi_driver = {
 	.driver = {
 		   .name = "arm-scmi",
diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
index 3c8ae7cc35de..4a8012e3cb8c 100644
--- a/drivers/firmware/arm_scmi/perf.c
+++ b/drivers/firmware/arm_scmi/perf.c
@@ -5,7 +5,10 @@
  * Copyright (C) 2018 ARM Ltd.
  */
 
+#include <linux/bits.h>
 #include <linux/of.h>
+#include <linux/io.h>
+#include <linux/io-64-nonatomic-hi-lo.h>
 #include <linux/platform_device.h>
 #include <linux/pm_opp.h>
 #include <linux/sort.h>
@@ -21,6 +24,7 @@ enum scmi_performance_protocol_cmd {
 	PERF_LEVEL_GET = 0x8,
 	PERF_NOTIFY_LIMITS = 0x9,
 	PERF_NOTIFY_LEVEL = 0xa,
+	PERF_DESCRIBE_FASTCHANNEL = 0xb,
 };
 
 struct scmi_opp {
@@ -44,6 +48,7 @@ struct scmi_msg_resp_perf_domain_attributes {
 #define SUPPORTS_SET_PERF_LVL(x)	((x) & BIT(30))
 #define SUPPORTS_PERF_LIMIT_NOTIFY(x)	((x) & BIT(29))
 #define SUPPORTS_PERF_LEVEL_NOTIFY(x)	((x) & BIT(28))
+#define SUPPORTS_PERF_FASTCHANNELS(x)	((x) & BIT(27))
 	__le32 rate_limit_us;
 	__le32 sustained_freq_khz;
 	__le32 sustained_perf_level;
@@ -87,17 +92,56 @@ struct scmi_msg_resp_perf_describe_levels {
 	} opp[0];
 };
 
+struct scmi_perf_get_fc_info {
+	__le32 domain;
+	__le32 message_id;
+};
+
+struct scmi_msg_resp_perf_desc_fc {
+	__le32 attr;
+#define SUPPORTS_DOORBELL(x)		((x) & BIT(0))
+#define DOORBELL_REG_WIDTH(x)		FIELD_GET(GENMASK(2, 1), (x))
+	__le32 rate_limit;
+	__le32 chan_addr_low;
+	__le32 chan_addr_high;
+	__le32 chan_size;
+	__le32 db_addr_low;
+	__le32 db_addr_high;
+	__le32 db_set_lmask;
+	__le32 db_set_hmask;
+	__le32 db_preserve_lmask;
+	__le32 db_preserve_hmask;
+};
+
+struct scmi_fc_db_info {
+	int width;
+	u64 set;
+	u64 mask;
+	void __iomem *addr;
+};
+
+struct scmi_fc_info {
+	void __iomem *level_set_addr;
+	void __iomem *limit_set_addr;
+	void __iomem *level_get_addr;
+	void __iomem *limit_get_addr;
+	struct scmi_fc_db_info *level_set_db;
+	struct scmi_fc_db_info *limit_set_db;
+};
+
 struct perf_dom_info {
 	bool set_limits;
 	bool set_perf;
 	bool perf_limit_notify;
 	bool perf_level_notify;
+	bool perf_fastchannels;
 	u32 opp_count;
 	u32 sustained_freq_khz;
 	u32 sustained_perf_level;
 	u32 mult_factor;
 	char name[SCMI_MAX_STR_SIZE];
 	struct scmi_opp opp[MAX_OPPS];
+	struct scmi_fc_info *fc_info;
 };
 
 struct scmi_perf_info {
@@ -151,7 +195,7 @@ scmi_perf_domain_attributes_get(const struct scmi_handle *handle, u32 domain,
 	if (ret)
 		return ret;
 
-	*(__le32 *)t->tx.buf = cpu_to_le32(domain);
+	put_unaligned_le32(domain, t->tx.buf);
 	attr = t->rx.buf;
 
 	ret = scmi_do_xfer(handle, t);
@@ -162,6 +206,7 @@ scmi_perf_domain_attributes_get(const struct scmi_handle *handle, u32 domain,
 		dom_info->set_perf = SUPPORTS_SET_PERF_LVL(flags);
 		dom_info->perf_limit_notify = SUPPORTS_PERF_LIMIT_NOTIFY(flags);
 		dom_info->perf_level_notify = SUPPORTS_PERF_LEVEL_NOTIFY(flags);
+		dom_info->perf_fastchannels = SUPPORTS_PERF_FASTCHANNELS(flags);
 		dom_info->sustained_freq_khz =
 					le32_to_cpu(attr->sustained_freq_khz);
 		dom_info->sustained_perf_level =
@@ -249,8 +294,42 @@ scmi_perf_describe_levels_get(const struct scmi_handle *handle, u32 domain,
 	return ret;
 }
 
-static int scmi_perf_limits_set(const struct scmi_handle *handle, u32 domain,
-				u32 max_perf, u32 min_perf)
+#define SCMI_PERF_FC_RING_DB(w)				\
+do {							\
+	u##w val = 0;					\
+							\
+	if (db->mask)					\
+		val = ioread##w(db->addr) & db->mask;	\
+	iowrite##w((u##w)db->set | val, db->addr);	\
+} while (0)
+
+static void scmi_perf_fc_ring_db(struct scmi_fc_db_info *db)
+{
+	if (!db || !db->addr)
+		return;
+
+	if (db->width == 1)
+		SCMI_PERF_FC_RING_DB(8);
+	else if (db->width == 2)
+		SCMI_PERF_FC_RING_DB(16);
+	else if (db->width == 4)
+		SCMI_PERF_FC_RING_DB(32);
+	else /* db->width == 8 */
+#ifdef CONFIG_64BIT
+		SCMI_PERF_FC_RING_DB(64);
+#else
+	{
+		u64 val = 0;
+
+		if (db->mask)
+			val = ioread64_hi_lo(db->addr) & db->mask;
+		iowrite64_hi_lo(db->set, db->addr);
+	}
+#endif
+}
+
+static int scmi_perf_mb_limits_set(const struct scmi_handle *handle, u32 domain,
+				   u32 max_perf, u32 min_perf)
 {
 	int ret;
 	struct scmi_xfer *t;
@@ -272,8 +351,24 @@ static int scmi_perf_limits_set(const struct scmi_handle *handle, u32 domain,
 	return ret;
 }
 
-static int scmi_perf_limits_get(const struct scmi_handle *handle, u32 domain,
-				u32 *max_perf, u32 *min_perf)
+static int scmi_perf_limits_set(const struct scmi_handle *handle, u32 domain,
+				u32 max_perf, u32 min_perf)
+{
+	struct scmi_perf_info *pi = handle->perf_priv;
+	struct perf_dom_info *dom = pi->dom_info + domain;
+
+	if (dom->fc_info && dom->fc_info->limit_set_addr) {
+		iowrite32(max_perf, dom->fc_info->limit_set_addr);
+		iowrite32(min_perf, dom->fc_info->limit_set_addr + 4);
+		scmi_perf_fc_ring_db(dom->fc_info->limit_set_db);
+		return 0;
+	}
+
+	return scmi_perf_mb_limits_set(handle, domain, max_perf, min_perf);
+}
+
+static int scmi_perf_mb_limits_get(const struct scmi_handle *handle, u32 domain,
+				   u32 *max_perf, u32 *min_perf)
 {
 	int ret;
 	struct scmi_xfer *t;
@@ -284,7 +379,7 @@ static int scmi_perf_limits_get(const struct scmi_handle *handle, u32 domain,
 	if (ret)
 		return ret;
 
-	*(__le32 *)t->tx.buf = cpu_to_le32(domain);
+	put_unaligned_le32(domain, t->tx.buf);
 
 	ret = scmi_do_xfer(handle, t);
 	if (!ret) {
@@ -298,8 +393,23 @@ static int scmi_perf_limits_get(const struct scmi_handle *handle, u32 domain,
 	return ret;
 }
 
-static int scmi_perf_level_set(const struct scmi_handle *handle, u32 domain,
-			       u32 level, bool poll)
+static int scmi_perf_limits_get(const struct scmi_handle *handle, u32 domain,
+				u32 *max_perf, u32 *min_perf)
+{
+	struct scmi_perf_info *pi = handle->perf_priv;
+	struct perf_dom_info *dom = pi->dom_info + domain;
+
+	if (dom->fc_info && dom->fc_info->limit_get_addr) {
+		*max_perf = ioread32(dom->fc_info->limit_get_addr);
+		*min_perf = ioread32(dom->fc_info->limit_get_addr + 4);
+		return 0;
+	}
+
+	return scmi_perf_mb_limits_get(handle, domain, max_perf, min_perf);
+}
+
+static int scmi_perf_mb_level_set(const struct scmi_handle *handle, u32 domain,
+				  u32 level, bool poll)
 {
 	int ret;
 	struct scmi_xfer *t;
@@ -321,8 +431,23 @@ static int scmi_perf_level_set(const struct scmi_handle *handle, u32 domain,
 	return ret;
 }
 
-static int scmi_perf_level_get(const struct scmi_handle *handle, u32 domain,
-