1 files changed, 50 insertions, 17 deletions

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index 84af8d7a4295..0b8d32829166 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -39,14 +39,22 @@
 #define EC_MSG_PREAMBLE_COUNT		32
 
 /*
-  * We must get a response from the EC in 5ms. This is a very long
-  * time, but the flash write command can take 2-3ms. The EC command
-  * processing is currently not very fast (about 500us). We could
-  * look at speeding this up and making the flash write command a
-  * 'slow' command, requiring a GET_STATUS wait loop, like flash
-  * erase.
-  */
-#define EC_MSG_DEADLINE_MS		5
+ * Allow for a long time for the EC to respond.  We support i2c
+ * tunneling and support fairly long messages for the tunnel (249
+ * bytes long at the moment).  If we're talking to a 100 kHz device
+ * on the other end and need to transfer ~256 bytes, then we need:
+ *  10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms
+ *
+ * We'll wait 4 times that to handle clock stretching and other
+ * paranoia.
+ *
+ * It's pretty unlikely that we'll really see a 249 byte tunnel in
+ * anything other than testing.  If this was more common we might
+ * consider having slow commands like this require a GET_STATUS
+ * wait loop.  The 'flash write' command would be another candidate
+ * for this, clocking in at 2-3ms.
+ */
+#define EC_MSG_DEADLINE_MS		100
 
 /*
   * Time between raising the SPI chip select (for the end of a
@@ -65,11 +73,13 @@
  *	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,
@@ -111,7 +121,9 @@ 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;
@@ -132,12 +144,19 @@ 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
@@ -208,6 +227,13 @@ 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);
 
@@ -219,7 +245,7 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
 		ktime_get_ts(&ts);
 		delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns;
 		if (delay < EC_SPI_RECOVERY_TIME_NS)
-			ndelay(delay);
+			ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
 	}
 
 	/* Transmit phase - send our message */
@@ -260,7 +286,7 @@ 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 +295,16 @@ 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 +321,14 @@ 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 +359,7 @@ 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;