mfd: cros ec: spi: Fix "in progress" error signaling

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-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index a14196e95e9b3a1c97e7f7234b530fc7c1ba278c..59c82cdcf48d8a508613dbc7b1c98654285de28f 100644 (file)
--- 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);