mfd: cros_ec: spi: Make the cros_ec_spi timeout more reliable

The cros_ec_spi transfer had two problems with its timeout code:

1. It looked at the timeout even in the case that it found valid data.
2. If the cros_ec_spi code got switched out for a while, it's possible
   it could get a timeout after a single loop.  Let's be paranoid and
   make sure we do one last transfer after the timeout expires.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Andrew Bresticker <abrestic@chromium.org>
Tested-by: Stephen Warren <swarren@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 a2a605de79a7c8504fde63ab4a14d694101b6a09..4f863c346547276de692640b94470ef9b9ccc244 100644 (file)
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -113,7 +113,9 @@ 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 {
+       while (true) {
+               unsigned long start_jiffies = jiffies;
+
                memset(&trans, 0, sizeof(trans));
                trans.cs_change = 1;
                trans.rx_buf = ptr = ec_dev->din;
@@ -134,12 +136,19 @@ 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