Merge tag 'mfd-fixes-4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd

Pull MFD fix from Lee Jones:
 "A single cros_ec_spi fix correcting the handling for long-running
  commands"

* tag 'mfd-fixes-4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd:
  mfd: cros_ec: Retry commands when EC is known to be busy

2 files changed, 22 insertions, 4 deletions

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index 1b52b8557034..2060d1483043 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -419,10 +419,25 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
                 /* Verify that EC can process command */
                 for (i = 0; i < len; i++) {
                         rx_byte = rx_buf[i];
+                        /*
+                         * Seeing the PAST_END, RX_BAD_DATA, or NOT_READY
+                         * markers are all signs that the EC didn't fully
+                         * receive our command. e.g., if the EC is flashing
+                         * itself, it can't respond to any commands and instead
+                         * clocks out EC_SPI_PAST_END from its SPI hardware
+                         * buffer. Similar occurrences can happen if the AP is
+                         * too slow to clock out data after asserting CS -- the
+                         * EC will abort and fill its buffer with
+                         * EC_SPI_RX_BAD_DATA.
+                         *
+                         * In all cases, these errors should be safe to retry.
+                         * Report -EAGAIN and let the caller decide what to do
+                         * about that.
+                         */
                         if (rx_byte == EC_SPI_PAST_END  ||
                             rx_byte == EC_SPI_RX_BAD_DATA ||
                             rx_byte == EC_SPI_NOT_READY) {
-                                ret = -EREMOTEIO;
+                                ret = -EAGAIN;
                                 break;
                         }
                 }
@@ -431,7 +446,7 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
         if (!ret)
                 ret = cros_ec_spi_receive_packet(ec_dev,
                                 ec_msg->insize + sizeof(*response));
-        else
+        else if (ret != -EAGAIN)
                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 
         final_ret = terminate_request(ec_dev);
@@ -537,10 +552,11 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
                 /* Verify that EC can process command */
                 for (i = 0; i < len; i++) {
                         rx_byte = rx_buf[i];
+                        /* See comments in cros_ec_pkt_xfer_spi() */
                         if (rx_byte == EC_SPI_PAST_END  ||
                             rx_byte == EC_SPI_RX_BAD_DATA ||
                             rx_byte == EC_SPI_NOT_READY) {
-                                ret = -EREMOTEIO;
+                                ret = -EAGAIN;
                                 break;
                         }
                 }
@@ -549,7 +565,7 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
         if (!ret)
                 ret = cros_ec_spi_receive_response(ec_dev,
                                 ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
-        else
+        else if (ret != -EAGAIN)
                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 
         final_ret = terminate_request(ec_dev);
diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index e7bbdf947bbc..8350ca2311c7 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -91,6 +91,8 @@ static int send_command(struct cros_ec_device *ec_dev,
                         usleep_range(10000, 11000);
 
                         ret = (*xfer_fxn)(ec_dev, status_msg);
+                        if (ret == -EAGAIN)
+                                continue;
                         if (ret < 0)
                                 break;