linux-kernel - [PATCH 2/3] cros_ec: Fix deadlock when EC is not responsive at probe

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Message-Id: <1485363674-25503-3-git-send-email-thierry.escande@collabora.com>
Date:   Wed, 25 Jan 2017 18:01:13 +0100
From:   Thierry Escande <thierry.escande@...labora.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Benson Leung <bleung@...omium.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] cros_ec: Fix deadlock when EC is not responsive at probe

From: Gwendal Grignou <gwendal@...omium.org>

When the EC is not responsive at probe, we try to get basic information
(protocol to use) later on through cros_xfer_cmd() call.
This patch makes sure there is no deadlock when re-probing the EC by
replacing call to cros_xfer_cmd() with send_command() in the function
cros_ec_get_host_command_version_mask(). Also, this patch adds the
function header indicating it must be called protected.

Signed-off-by: Gwendal Grignou <gwendal@...omium.org>
Signed-off-by: Thierry Escande <thierry.escande@...labora.com>
---
 drivers/platform/chrome/cros_ec_proto.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 403649a..256249b 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -235,6 +235,22 @@ static int cros_ec_host_command_proto_query_v2(struct cros_ec_device *ec_dev)
 	return ret;
 }
 
+/*
+ * cros_ec_get_host_command_version_mask
+ *
+ * Get the version mask of a given command.
+ *
+ * @ec_dev: EC device to call
+ * @msg: message structure to use
+ * @cmd: command to get the version of.
+ * @mask: result when function returns 0.
+ *
+ * @return 0 on success, error code otherwise
+ *
+ * LOCKING:
+ * the caller has ec_dev->lock mutex or the caller knows there is
+ * no other command in progress.
+ */
 static int cros_ec_get_host_command_version_mask(struct cros_ec_device *ec_dev,
 	u16 cmd, u32 *mask)
 {
@@ -256,7 +272,7 @@ static int cros_ec_get_host_command_version_mask(struct cros_ec_device *ec_dev,
 	pver = (struct ec_params_get_cmd_versions *)msg->data;
 	pver->cmd = cmd;
 
-	ret = cros_ec_cmd_xfer(ec_dev, msg);
+	ret = send_command(ec_dev, msg);
 	if (ret > 0) {
 		rver = (struct ec_response_get_cmd_versions *)msg->data;
 		*mask = rver->version_mask;
-- 
2.7.4