staging: wfx: add IRQ handling

bh_work() is in charge to schedule all HIF message from/to chip.

On normal operation, when an IRQ is received, driver can get size of
next message in control register. In order to save control register
access, when chip send a message, it also appends a copy of control
register after the message (this register is not accounted in message
length declared in message header, but must accounted in bus request).
This copy of control register is called "piggyback".

It also handles a power saving mechanism specific to WFxxx series. This
mechanism is based on a GPIO called "wakeup" GPIO. Obviously, this gpio
is not part of SPI/SDIO standard buses and must be declared
independently (this is the main reason for why SDIO mode try to get
parameters from DT).

When wakeup is enabled, host can communicate with chip only if it is
awake. To wake up chip, there are two cases:
    - host receive an IRQ from chip (chip initiate communication): host
      just have to set wakeup GPIO before reading data
    - host want to send data to chip: host set wakeup GPIO, then wait
      for an IRQ (in fact, wait for an empty message) and finally send data

bh_work() is also in charge to track usage of chip buffers. Normally
each request expect a confirmation. However, you can notice that special
"multi tx" confirmation can acknowledge multiple requests at time.

Finally, note that wfx_bh_request_rx() is not atomic (because of
control_reg_read()). So, in SPI mode, hard-irq handler only postpone all
processing to wfx_spi_request_rx().

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20190919142527.31797-8-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 277 insertions, 0 deletions

diff --git a/drivers/staging/wfx/bh.c b/drivers/staging/wfx/bh.c
new file mode 100644
index 000000000000..02a42e5c1e10
--- /dev/null
+++ b/drivers/staging/wfx/bh.c
@@ -0,0 +1,277 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Interrupt bottom half (BH).
+ *
+ * Copyright (c) 2017-2019, Silicon Laboratories, Inc.
+ * Copyright (c) 2010, ST-Ericsson
+ */
+#include <linux/gpio/consumer.h>
+#include <net/mac80211.h>
+
+#include "bh.h"
+#include "wfx.h"
+#include "hwio.h"
+#include "hif_api_cmd.h"
+
+static void device_wakeup(struct wfx_dev *wdev)
+{
+	if (!wdev->pdata.gpio_wakeup)
+		return;
+	if (gpiod_get_value(wdev->pdata.gpio_wakeup))
+		return;
+
+	gpiod_set_value(wdev->pdata.gpio_wakeup, 1);
+	if (wfx_api_older_than(wdev, 1, 4)) {
+		if (!completion_done(&wdev->hif.ctrl_ready))
+			udelay(2000);
+	} else {
+		// completion.h does not provide any function to wait
+		// completion without consume it (a kind of
+		// wait_for_completion_done_timeout()). So we have to emulate
+		// it.
+		if (wait_for_completion_timeout(&wdev->hif.ctrl_ready, msecs_to_jiffies(2) + 1))
+			complete(&wdev->hif.ctrl_ready);
+		else
+			dev_err(wdev->dev, "timeout while wake up chip\n");
+	}
+}
+
+static void device_release(struct wfx_dev *wdev)
+{
+	if (!wdev->pdata.gpio_wakeup)
+		return;
+
+	gpiod_set_value(wdev->pdata.gpio_wakeup, 0);
+}
+
+static int rx_helper(struct wfx_dev *wdev, size_t read_len, int *is_cnf)
+{
+	struct sk_buff *skb;
+	struct hif_msg *hif;
+	size_t alloc_len;
+	size_t computed_len;
+	int release_count;
+	int piggyback = 0;
+
+	WARN_ON(read_len < 4);
+	WARN(read_len > round_down(0xFFF, 2) * sizeof(u16),
+	     "%s: request exceed WFx capability", __func__);
+
+	// Add 2 to take into account piggyback size
+	alloc_len = wdev->hwbus_ops->align_size(wdev->hwbus_priv, read_len + 2);
+	skb = dev_alloc_skb(alloc_len);
+	if (!skb)
+		return -ENOMEM;
+
+	if (wfx_data_read(wdev, skb->data, alloc_len))
+		goto err;
+
+	piggyback = le16_to_cpup((u16 *) (skb->data + alloc_len - 2));
+
+	hif = (struct hif_msg *) skb->data;
+	WARN(hif->encrypted & 0x1, "unsupported encryption type");
+	if (hif->encrypted == 0x2) {
+		BUG(); // Not yet implemented
+	} else {
+		le16_to_cpus(hif->len);
+		computed_len = round_up(hif->len, 2);
+	}
+	if (computed_len != read_len) {
+		dev_err(wdev->dev, "inconsistent message length: %zu != %zu\n",
+			computed_len, read_len);
+		print_hex_dump(KERN_INFO, "hif: ", DUMP_PREFIX_OFFSET, 16, 1,
+			       hif, read_len, true);
+		goto err;
+	}
+
+	if (!(hif->id & HIF_ID_IS_INDICATION)) {
+		(*is_cnf)++;
+		if (hif->id == HIF_CNF_ID_MULTI_TRANSMIT)
+			release_count = le32_to_cpu(((struct hif_cnf_multi_transmit *) hif->body)->num_tx_confs);
+		else
+			release_count = 1;
+		WARN(wdev->hif.tx_buffers_used < release_count, "corrupted buffer counter");
+		wdev->hif.tx_buffers_used -= release_count;
+		if (!wdev->hif.tx_buffers_used)
+			wake_up(&wdev->hif.tx_buffers_empty);
+	}
+
+	if (hif->id != HIF_IND_ID_EXCEPTION && hif->id != HIF_IND_ID_ERROR) {
+		if (hif->seqnum != wdev->hif.rx_seqnum)
+			dev_warn(wdev->dev, "wrong message sequence: %d != %d\n",
+				 hif->seqnum, wdev->hif.rx_seqnum);
+		wdev->hif.rx_seqnum = (hif->seqnum + 1) % (HIF_COUNTER_MAX + 1);
+	}
+
+	skb_put(skb, hif->len);
+	dev_kfree_skb(skb); /* FIXME: handle received data */
+
+	return piggyback;
+
+err:
+	if (skb)
+		dev_kfree_skb(skb);
+	return -EIO;
+}
+
+static int bh_work_rx(struct wfx_dev *wdev, int max_msg, int *num_cnf)
+{
+	size_t len;
+	int i;
+	int ctrl_reg, piggyback;
+
+	piggyback = 0;
+	for (i = 0; i < max_msg; i++) {
+		if (piggyback & CTRL_NEXT_LEN_MASK)
+			ctrl_reg = piggyback;
+		else if (try_wait_for_completion(&wdev->hif.ctrl_ready))
+			ctrl_reg = atomic_xchg(&wdev->hif.ctrl_reg, 0);
+		else
+			ctrl_reg = 0;
+		if (!(ctrl_reg & CTRL_NEXT_LEN_MASK))
+			return i;
+		// ctrl_reg units are 16bits words
+		len = (ctrl_reg & CTRL_NEXT_LEN_MASK) * 2;
+		piggyback = rx_helper(wdev, len, num_cnf);
+		if (piggyback < 0)
+			return i;
+		if (!(piggyback & CTRL_WLAN_READY))
+			dev_err(wdev->dev, "unexpected piggyback value: ready bit not set: %04x\n",
+				piggyback);
+	}
+	if (piggyback & CTRL_NEXT_LEN_MASK) {
+		ctrl_reg = atomic_xchg(&wdev->hif.ctrl_reg, piggyback);
+		complete(&wdev->hif.ctrl_ready);
+		if (ctrl_reg)
+			dev_err(wdev->dev, "unexpected IRQ happened: %04x/%04x\n",
+				ctrl_reg, piggyback);
+	}
+	return i;
+}
+
+static void tx_helper(struct wfx_dev *wdev, struct hif_msg *hif)
+{
+	int ret;
+	void *data;
+	bool is_encrypted = false;
+	size_t len = le16_to_cpu(hif->len);
+
+	BUG_ON(len < sizeof(*hif));
+
+	hif->seqnum = wdev->hif.tx_seqnum;
+	wdev->hif.tx_seqnum = (wdev->hif.tx_seqnum + 1) % (HIF_COUNTER_MAX + 1);
+
+	data = hif;
+	WARN(len > wdev->hw_caps.size_inp_ch_buf,
+	     "%s: request exceed WFx capability: %zu > %d\n", __func__,
+	     len, wdev->hw_caps.size_inp_ch_buf);
+	len = wdev->hwbus_ops->align_size(wdev->hwbus_priv, len);
+	ret = wfx_data_write(wdev, data, len);
+	if (ret)
+		goto end;
+
+	wdev->hif.tx_buffers_used++;
+end:
+	if (is_encrypted)
+		kfree(data);
+}
+
+static int bh_work_tx(struct wfx_dev *wdev, int max_msg)
+{
+	struct hif_msg *hif;
+	int i;
+
+	for (i = 0; i < max_msg; i++) {
+		hif = NULL;
+		if (wdev->hif.tx_buffers_used < wdev->hw_caps.num_inp_ch_bufs) {
+			/* FIXME: get queued data */
+		}
+		if (!hif)
+			return i;
+		tx_helper(wdev, hif);
+	}
+	return i;
+}
+
+/* In SDIO mode, it is necessary to make an access to a register to acknowledge
+ * last received message. It could be possible to restrict this acknowledge to
+ * SDIO mode and only if last operation was rx.
+ */
+static void ack_sdio_data(struct wfx_dev *wdev)
+{
+	uint32_t cfg_reg;
+
+	config_reg_read(wdev, &cfg_reg);
+	if (cfg_reg & 0xFF) {
+		dev_warn(wdev->dev, "chip reports errors: %02x\n", cfg_reg & 0xFF);
+		config_reg_write_bits(wdev, 0xFF, 0x00);
+	}
+}
+
+static void bh_work(struct work_struct *work)
+{
+	struct wfx_dev *wdev = container_of(work, struct wfx_dev, hif.bh);
+	int stats_req = 0, stats_cnf = 0, stats_ind = 0;
+	bool release_chip = false, last_op_is_rx = false;
+	int num_tx, num_rx;
+
+	device_wakeup(wdev);
+	do {
+		num_tx = bh_work_tx(wdev, 32);
+		stats_req += num_tx;
+		if (num_tx)
+			last_op_is_rx = false;
+		num_rx = bh_work_rx(wdev, 32, &stats_cnf);
+		stats_ind += num_rx;
+		if (num_rx)
+			last_op_is_rx = true;
+	} while (num_rx || num_tx);
+	stats_ind -= stats_cnf;
+
+	if (last_op_is_rx)
+		ack_sdio_data(wdev);
+	if (!wdev->hif.tx_buffers_used && !work_pending(work)) {
+		device_release(wdev);
+		release_chip = true;
+	}
+}
+
+/*
+ * An IRQ from chip did occur
+ */
+void wfx_bh_request_rx(struct wfx_dev *wdev)
+{
+	u32 cur, prev;
+
+	control_reg_read(wdev, &cur);
+	prev = atomic_xchg(&wdev->hif.ctrl_reg, cur);
+	complete(&wdev->hif.ctrl_ready);
+	queue_work(system_highpri_wq, &wdev->hif.bh);
+
+	if (!(cur & CTRL_NEXT_LEN_MASK))
+		dev_err(wdev->dev, "unexpected control register value: length field is 0: %04x\n",
+			cur);
+	if (prev != 0)
+		dev_err(wdev->dev, "received IRQ but previous data was not (yet) read: %04x/%04x\n",
+			prev, cur);
+}
+
+/*
+ * Driver want to send data
+ */
+void wfx_bh_request_tx(struct wfx_dev *wdev)
+{
+	queue_work(system_highpri_wq, &wdev->hif.bh);
+}
+
+void wfx_bh_register(struct wfx_dev *wdev)
+{
+	INIT_WORK(&wdev->hif.bh, bh_work);
+	init_completion(&wdev->hif.ctrl_ready);
+	init_waitqueue_head(&wdev->hif.tx_buffers_empty);
+}
+
+void wfx_bh_unregister(struct wfx_dev *wdev)
+{
+	flush_work(&wdev->hif.bh);
+}