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/*
* ChromeOS EC multi-function device (SPI)
*
* Copyright (C) 2012 Google, Inc
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mfd/cros_ec.h>
#include <linux/mfd/cros_ec_commands.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
/* The header byte, which follows the preamble */
#define EC_MSG_HEADER 0xec
/*
* Number of EC preamble bytes we read at a time. Since it takes
* about 400-500us for the EC to respond there is not a lot of
* point in tuning this. If the EC could respond faster then
* we could increase this so that might expect the preamble and
* message to occur in a single transaction. However, the maximum
* SPI transfer size is 256 bytes, so at 5MHz we need a response
* time of perhaps <320us (200 bytes / 1600 bits).
*/
#define EC_MSG_PREAMBLE_COUNT 32
/*
* Allow for a long time for the EC to respond. We support i2c
* tunneling and support fairly long messages for the tunnel (249
* bytes long at the moment). If we're talking to a 100 kHz device
* on the other end and need to transfer ~256 bytes, then we need:
* 10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms
*
* We'll wait 4 times that to handle clock stretching and other
* paranoia.
*
* It's pretty unlikely that we'll really see a 249 byte tunnel in
* anything other than testing. If this was more common we might
* consider having slow commands like this require a GET_STATUS
* wait loop. The 'flash write' command would be another candidate
* for this, clocking in at 2-3ms.
*/
#define EC_MSG_DEADLINE_MS 100
/*
* Time between raising the SPI chip select (for the end of a
* transaction) and dropping it again (for the next transaction).
* If we go too fast, the EC will miss the transaction. We know that we
* need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be
* safe.
*/
#define EC_SPI_RECOVERY_TIME_NS (200 * 1000)
/**
* struct cros_ec_spi - information about a SPI-connected EC
*
* @spi: SPI device we are connected to
* @last_transfer_ns: time that we last finished a transfer, or 0 if there
* if no record
* @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
* is sent when we want to turn on CS at the start of a transaction.
* @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
* is sent when we want to turn off CS at the end of a transaction.
*/
struct cros_ec_spi {
struct spi_device *spi;
s64 last_transfer_ns;
unsigned int start_of_msg_delay;
unsigned int end_of_msg_delay;
};
static void debug_packet(struct device *dev, const char *name, u8 *ptr,
int len)
{
#ifdef DEBUG
int i;
dev_dbg(dev, "%s: ", name);
for (i = 0; i < len; i++)
pr_cont(" %02x", ptr[i]);
pr_cont("\n");
#endif
}
static int terminate_request(struct cros_ec_device *ec_dev)
{
struct cros_ec_spi *ec_spi = ec_dev->priv;
struct spi_message msg;
struct spi_transfer trans;
int ret;
/*
* Turn off CS, possibly adding a delay to ensure the rising edge
* doesn't come too soon after the end of the data.
*/
spi_message_init(&msg);
memset(&trans, 0, sizeof(trans));
trans.delay_usecs = ec_spi->end_of_msg_delay;
spi_message_add_tail(&trans, &msg);
ret = spi_sync(ec_spi->spi, &msg);
/* Reset end-of-response timer */
ec_spi->last_transfer_ns = ktime_get_ns();
if (ret < 0) {
dev_err(ec_dev->dev,
"cs-deassert spi transfer failed: %d\n",
ret);
}
return ret;
}
/**
* receive_n_bytes - receive n bytes from the EC.
*
* Assumes buf is a pointer into the ec_dev->din buffer
*/
static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
{
struct cros_ec_spi *ec_spi = ec_dev->priv;
struct spi_transfer trans;
struct spi_message msg;
int ret;
BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);
memset(&trans, 0, sizeof(trans));
trans.cs_change = 1;
trans.rx_buf = buf;
trans.len = n;
spi_message_init(&msg);
spi_message_add_tail(&trans, &msg);
ret = spi_sync(ec_spi->spi, &msg);
if (ret < 0)
dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
return ret;
}
/**
* cros_ec_spi_receive_packet - Receive a packet from the EC.
*
* This function has two phases: reading the preamble bytes (since if we read
* data from the EC before it is ready to send, we just get preamble) and
* reading the actual message.
*
* The received data is placed into ec_dev->din.
*
* @ec_dev: ChromeOS EC device
* @need_len: Number of message bytes we need to read
*/
static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
int need_len)
{
struct ec_host_response *response;
u8 *ptr, *end;
int ret;
unsigned long deadline;
int todo;
BUG_ON(EC_MSG_PREAMBLE_COUNT > ec_dev->din_size);
/* Receive data until we see the header byte */
deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
while (true) {
unsigned long start_jiffies = jiffies;
ret = receive_n_bytes(ec_dev,
ec_dev->din,
EC_MSG_PREAMBLE_COUNT);
if (ret < 0)
return ret;
ptr = ec_dev->din;
for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
if (*ptr == EC_SPI_FRAME_START) {
dev_dbg(ec_dev->dev, "msg found at %zd\n",
ptr - ec_dev->din);
break;
}
}
if (ptr != end)
break;
/*
* Use the time at the start of the loop as a timeout. This
* gives us one last shot at getting the transfer and is useful
* in case we got context switched out for a while.
*/
if (time_after(start_jiffies, deadline)) {
dev_warn(ec_dev->dev, "EC failed to respond in time\n");
return -ETIMEDOUT;
}
}
/*
* ptr now points to the header byte. Copy any valid data to the
* start of our buffer
*/
todo = end - ++ptr;
BUG_ON(todo < 0 || todo > ec_dev->din_size);
todo = min(todo, need_len);
memmove(ec_dev->din, ptr, todo);
ptr = ec_dev->din + todo;
dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
need_len, todo);
need_len -= todo;
/* If the entire response struct wasn't read, get the rest of it. */
if (todo < sizeof(*response)) {
ret = receive_n_bytes(ec_dev, ptr, sizeof(*response) - todo);
if (ret < 0)
return -EBADMSG;
ptr += (sizeof(*response) - todo);
todo = sizeof(*response);
}
response = (struct ec_host_response *)ec_dev->din;
/* Abort if data_len is too large. */
if (response->data_len > ec_dev->din_size)
return -EMSGSIZE;
/* Receive data until we have it all */
while (need_len > 0) {
/*
* We can't support transfers larger than the SPI FIFO size
* unless we have DMA. We don't have DMA on the ISP SPI ports
* for Exynos. We need a way of asking SPI driver for
* maximum-supported transfer size.
*/
todo =
|