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Subject[PATCH] mfd: cros ec: spi: Fix "in progress" error signaling
Date
For host commands that take a long time to process, cros ec can return
early by signaling a EC_RES_IN_PROGRESS result. The host must then poll
status with EC_CMD_GET_COMMS_STATUS until completion of the command.

None of the above applies when data link errors are encountered. When
errors such as EC_SPI_PAST_END are encountered during command
transmission, it usually means the command was not received by the EC.
Treating such errors as if they were 'EC_RES_IN_PROGRESS' results is
almost always the wrong decision, and can result in host commands
silently being lost.

Reported-and-tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
---
drivers/mfd/cros_ec_spi.c | 52 ++++++++++++++++++++++-------------------------
1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index c9714072e224..d019b5b00b67 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -377,6 +377,7 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
u8 *ptr;
u8 *rx_buf;
u8 sum;
+ u8 rx_byte;
int ret = 0, final_ret;

len = cros_ec_prepare_tx(ec_dev, ec_msg);
@@ -421,25 +422,22 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
if (!ret) {
/* Verify that EC can process command */
for (i = 0; i < len; i++) {
- switch (rx_buf[i]) {
- case EC_SPI_PAST_END:
- case EC_SPI_RX_BAD_DATA:
- case EC_SPI_NOT_READY:
- ret = -EAGAIN;
- ec_msg->result = EC_RES_IN_PROGRESS;
- default:
+ rx_byte = rx_buf[i];
+ if (rx_byte == EC_SPI_PAST_END ||
+ rx_byte == EC_SPI_RX_BAD_DATA ||
+ rx_byte == EC_SPI_NOT_READY) {
+ ret = -EREMOTEIO;
break;
}
- if (ret)
- break;
}
- if (!ret)
- ret = cros_ec_spi_receive_packet(ec_dev,
- ec_msg->insize + sizeof(*response));
- } else {
- dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
}

+ if (!ret)
+ ret = cros_ec_spi_receive_packet(ec_dev,
+ ec_msg->insize + sizeof(*response));
+ else
+ dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
+
final_ret = terminate_request(ec_dev);

spi_bus_unlock(ec_spi->spi->master);
@@ -508,6 +506,7 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
int i, len;
u8 *ptr;
u8 *rx_buf;
+ u8 rx_byte;
int sum;
int ret = 0, final_ret;

@@ -544,25 +543,22 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
if (!ret) {
/* Verify that EC can process command */
for (i = 0; i < len; i++) {
- switch (rx_buf[i]) {
- case EC_SPI_PAST_END:
- case EC_SPI_RX_BAD_DATA:
- case EC_SPI_NOT_READY:
- ret = -EAGAIN;
- ec_msg->result = EC_RES_IN_PROGRESS;
- default:
+ rx_byte = rx_buf[i];
+ if (rx_byte == EC_SPI_PAST_END ||
+ rx_byte == EC_SPI_RX_BAD_DATA ||
+ rx_byte == EC_SPI_NOT_READY) {
+ ret = -EREMOTEIO;
break;
}
- if (ret)
- break;
}
- if (!ret)
- ret = cros_ec_spi_receive_response(ec_dev,
- ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
- } else {
- dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
}

+ if (!ret)
+ ret = cros_ec_spi_receive_response(ec_dev,
+ ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
+ else
+ dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
+
final_ret = terminate_request(ec_dev);

spi_bus_unlock(ec_spi->spi->master);
--
2.12.2
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