diff options
Diffstat (limited to 'drivers/mfd/cros_ec_spi.c')
| -rw-r--r-- | drivers/mfd/cros_ec_spi.c | 123 |
1 files changed, 94 insertions, 29 deletions
diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c index 367ccb58ecb..0b8d3282916 100644 --- a/drivers/mfd/cros_ec_spi.c +++ b/drivers/mfd/cros_ec_spi.c @@ -18,6 +18,7 @@ #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> @@ -38,22 +39,31 @@ #define EC_MSG_PREAMBLE_COUNT 32 /* - * We must get a response from the EC in 5ms. This is a very long - * time, but the flash write command can take 2-3ms. The EC command - * processing is currently not very fast (about 500us). We could - * look at speeding this up and making the flash write command a - * 'slow' command, requiring a GET_STATUS wait loop, like flash - * erase. - */ -#define EC_MSG_DEADLINE_MS 5 + * 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. It seems - * that 50us is enough with the 16MHz STM32 EC. + * 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 (50 * 1000) +#define EC_SPI_RECOVERY_TIME_NS (200 * 1000) /** * struct cros_ec_spi - information about a SPI-connected EC @@ -61,10 +71,15 @@ * @spi: SPI device we are connected to * @last_transfer_ns: time that we last finished a transfer, or 0 if there * if no record + * @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. + * @lock: mutex to ensure only one user of cros_ec_command_spi_xfer at a time */ struct cros_ec_spi { struct spi_device *spi; s64 last_transfer_ns; + unsigned int end_of_msg_delay; + struct mutex lock; }; static void debug_packet(struct device *dev, const char *name, u8 *ptr, @@ -75,7 +90,9 @@ static void debug_packet(struct device *dev, const char *name, u8 *ptr, dev_dbg(dev, "%s: ", name); for (i = 0; i < len; i++) - dev_cont(dev, " %02x", ptr[i]); + pr_cont(" %02x", ptr[i]); + + pr_cont("\n"); #endif } @@ -104,8 +121,10 @@ static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev, /* Receive data until we see the header byte */ deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS); - do { - memset(&trans, '\0', sizeof(trans)); + while (true) { + unsigned long start_jiffies = jiffies; + + memset(&trans, 0, sizeof(trans)); trans.cs_change = 1; trans.rx_buf = ptr = ec_dev->din; trans.len = EC_MSG_PREAMBLE_COUNT; @@ -125,12 +144,19 @@ static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev, break; } } + if (ptr != end) + break; - if (time_after(jiffies, deadline)) { + /* + * 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; } - } while (ptr == end); + } /* * ptr now points to the header byte. Copy any valid data to the @@ -157,7 +183,7 @@ static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev, dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n", todo, need_len, ptr - ec_dev->din); - memset(&trans, '\0', sizeof(trans)); + memset(&trans, 0, sizeof(trans)); trans.cs_change = 1; trans.rx_buf = ptr; trans.len = todo; @@ -201,6 +227,13 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, int ret = 0, final_ret; struct timespec ts; + /* + * We have the shared ec_dev buffer plus we do lots of separate spi_sync + * calls, so we need to make sure only one person is using this at a + * time. + */ + mutex_lock(&ec_spi->lock); + len = cros_ec_prepare_tx(ec_dev, ec_msg); dev_dbg(ec_dev->dev, "prepared, len=%d\n", len); @@ -212,12 +245,12 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, ktime_get_ts(&ts); delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns; if (delay < EC_SPI_RECOVERY_TIME_NS) - ndelay(delay); + ndelay(EC_SPI_RECOVERY_TIME_NS - delay); } /* Transmit phase - send our message */ debug_packet(ec_dev->dev, "out", ec_dev->dout, len); - memset(&trans, '\0', sizeof(trans)); + memset(&trans, 0, sizeof(trans)); trans.tx_buf = ec_dev->dout; trans.len = len; trans.cs_change = 1; @@ -235,6 +268,17 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, /* turn off CS */ spi_message_init(&msg); + + if (ec_spi->end_of_msg_delay) { + /* + * Add delay for last transaction, to ensure the rising edge + * doesn't come too soon after the end of the data. + */ + memset(&trans, 0, sizeof(trans)); + trans.delay_usecs = ec_spi->end_of_msg_delay; + spi_message_add_tail(&trans, &msg); + } + final_ret = spi_sync(ec_spi->spi, &msg); ktime_get_ts(&ts); ec_spi->last_transfer_ns = timespec_to_ns(&ts); @@ -242,7 +286,7 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, ret = final_ret; if (ret < 0) { dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); - return ret; + goto exit; } /* check response error code */ @@ -251,14 +295,16 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n", ec_msg->cmd, ptr[0]); debug_packet(ec_dev->dev, "in_err", ptr, len); - return -EINVAL; + ret = -EINVAL; + goto exit; } len = ptr[1]; sum = ptr[0] + ptr[1]; if (len > ec_msg->in_len) { dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)", len, ec_msg->in_len); - return -ENOSPC; + ret = -ENOSPC; + goto exit; } /* copy response packet payload and compute checksum */ @@ -275,13 +321,28 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, dev_err(ec_dev->dev, "bad packet checksum, expected %02x, got %02x\n", sum, ptr[len + 2]); - return -EBADMSG; + ret = -EBADMSG; + goto exit; } - return 0; + ret = 0; +exit: + mutex_unlock(&ec_spi->lock); + return ret; } -static int cros_ec_probe_spi(struct spi_device *spi) +static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev) +{ + struct device_node *np = dev->of_node; + u32 val; + int ret; + + ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val); + if (!ret) + ec_spi->end_of_msg_delay = val; +} + +static int cros_ec_spi_probe(struct spi_device *spi) { struct device *dev = &spi->dev; struct cros_ec_device *ec_dev; @@ -298,10 +359,14 @@ static int cros_ec_probe_spi(struct spi_device *spi) if (ec_spi == NULL) return -ENOMEM; ec_spi->spi = spi; + mutex_init(&ec_spi->lock); ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL); if (!ec_dev) return -ENOMEM; + /* Check for any DT properties */ + cros_ec_spi_dt_probe(ec_spi, dev); + spi_set_drvdata(spi, ec_dev); ec_dev->name = "SPI"; ec_dev->dev = dev; @@ -323,7 +388,7 @@ static int cros_ec_probe_spi(struct spi_device *spi) return 0; } -static int cros_ec_remove_spi(struct spi_device *spi) +static int cros_ec_spi_remove(struct spi_device *spi) { struct cros_ec_device *ec_dev; @@ -364,12 +429,12 @@ static struct spi_driver cros_ec_driver_spi = { .owner = THIS_MODULE, .pm = &cros_ec_spi_pm_ops, }, - .probe = cros_ec_probe_spi, - .remove = cros_ec_remove_spi, + .probe = cros_ec_spi_probe, + .remove = cros_ec_spi_remove, .id_table = cros_ec_spi_id, }; module_spi_driver(cros_ec_driver_spi); -MODULE_LICENSE("GPL"); +MODULE_LICENSE("GPL v2"); MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)"); |