linux-kernel - [PATCH v3] cros_ec_i2c: prevent i2c timeout for EC_CMD_FLASH

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Message-Id: <20170515180138.91592-1-wnhuang@google.com>
Date:   Tue, 16 May 2017 02:01:38 +0800
From:   Wei-Ning Huang <wnhuang@...omium.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Douglas Anderson <dianders@...gle.com>,
        Duncan Laurie <dlaurie@...gle.com>,
        Andrew de los Reyes <adlr@...gle.com>,
        Wei-Ning Huang <wnhuang@...omium.org>, lee.jones@...aro.org
Subject: [PATCH v3] cros_ec_i2c: prevent i2c timeout for EC_CMD_FLASH_ERASE

From: Wei-Ning Huang <wnhuang@...omium.org>

Some EC chip has larger flash sector size which requires longer erase
time. During erase the CPU is usually stalled and can't even respond to
interrupts. We sleep a while to block any EC command from executing
during the flash erase period.

Signed-off-by: Wei-Ning Huang <wnhuang@...omium.org>
---
 drivers/mfd/cros_ec_i2c.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/cros_ec_i2c.c b/drivers/mfd/cros_ec_i2c.c
index 9f70de1e4c70..c1b5c831b9cb 100644
--- a/drivers/mfd/cros_ec_i2c.c
+++ b/drivers/mfd/cros_ec_i2c.c
@@ -23,6 +23,14 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 
+/*
+ * Some EC chip has larger flash sector size which requires longer erase time.
+ * During erase the CPU is usually stalled and can't even respond to
+ * interrupts. We sleep for a while to block any EC command from executing
+ * during the flash erase period to prevent i2c timeout.
+ */
+#define EC_FLASH_ERASE_DELAY_MS	5000
+
 /**
  * Request format for protocol v3
  * byte 0	0xda (EC_COMMAND_PROTOCOL_3)
@@ -120,7 +128,7 @@ static int cros_ec_pkt_xfer_i2c(struct cros_ec_device *ec_dev,
 		ret = -EAGAIN;
 		dev_dbg(ec_dev->dev, "command 0x%02x in progress\n",
 			msg->command);
-		goto done;
+		goto inprogress;
 
 	default:
 		dev_dbg(ec_dev->dev, "command 0x%02x returned %d\n",
@@ -177,7 +185,19 @@ static int cros_ec_pkt_xfer_i2c(struct cros_ec_device *ec_dev,
 
 	ret = ec_response->data_len;
 
+inprogress:
+	/*
+	 * If we get EC_RES_IN_PROGRESS for EC_CMD_FLASH_ERASE this means EC
+	 * need a long time to erase flash, during flash erase CPU is stalled
+	 * and can't respond to interrupts, so we sleep for a while to stop new
+	 * EC commands from communicating with EC.
+	 */
+	if (msg->command == EC_CMD_FLASH_ERASE &&
+	    msg->result == EC_RES_IN_PROGRESS)
+		msleep(EC_FLASH_ERASE_DELAY_MS);
+
 done:
+
 	if (msg->command == EC_CMD_REBOOT_EC)
 		msleep(EC_REBOOT_DELAY_MS);
 
-- 
2.12.2