[PATCH 2/7] mfd: cros_ec: spi: Add mutex to cros_ec_spi

From: Doug Anderson
Date: Thu Apr 17 2014 - 14:01:37 EST


The main transfer function for cros_ec_spi can be called by more than
one client at a time. Make sure that those clients don't stomp on
each other by locking the bus for the duration of the transfer
function.

Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
---
drivers/mfd/cros_ec_spi.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index c185eb6..a2a605d 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -65,11 +65,13 @@
* 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,
@@ -208,6 +210,13 @@ 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);

@@ -260,7 +269,7 @@ 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 */
@@ -269,14 +278,16 @@ 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 */
@@ -293,10 +304,14 @@ 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 void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
@@ -327,6 +342,7 @@ static int cros_ec_spi_probe(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;
--
1.9.1.423.g4596e3a

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/