linux-kernel - [PATCH 1/3] Input: applespi: Don't wait for responses to commands indefinitely.

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Date:   Wed, 17 Feb 2021 11:07:16 -0800
From:   Ronald Tschalär <ronald@...ovation.ch>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Sergiu Cuciurean <sergiu.cuciurean@...log.com>,
        Lee Jones <lee.jones@...aro.org>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] Input: applespi: Don't wait for responses to commands indefinitely.

The response to a command may never arrive or it may be corrupted (and
hence dropped) for some reason. While exceedingly rare, when it did
happen it blocked all further commands. One way to fix this was to
do a suspend/resume. However, recovering automatically seems like a
nicer option. Hence this puts a time limit (1 sec) on how long we're
willing to wait for a response, after which we assume it got lost.

Signed-off-by: Ronald Tschalär <ronald@...ovation.ch>
---
 drivers/input/keyboard/applespi.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/input/keyboard/applespi.c b/drivers/input/keyboard/applespi.c
index d22223154177f..8494bf610fd70 100644
--- a/drivers/input/keyboard/applespi.c
+++ b/drivers/input/keyboard/applespi.c
@@ -48,6 +48,7 @@
 #include <linux/efi.h>
 #include <linux/input.h>
 #include <linux/input/mt.h>
+#include <linux/ktime.h>
 #include <linux/leds.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
@@ -409,7 +410,7 @@ struct applespi_data {
 	unsigned int			cmd_msg_cntr;
 	/* lock to protect the above parameters and flags below */
 	spinlock_t			cmd_msg_lock;
-	bool				cmd_msg_queued;
+	ktime_t				cmd_msg_queued;
 	enum applespi_evt_type		cmd_evt_type;
 
 	struct led_classdev		backlight_info;
@@ -729,7 +730,7 @@ static void applespi_msg_complete(struct applespi_data *applespi,
 		wake_up_all(&applespi->drain_complete);
 
 	if (is_write_msg) {
-		applespi->cmd_msg_queued = false;
+		applespi->cmd_msg_queued = 0;
 		applespi_send_cmd_msg(applespi);
 	}
 
@@ -771,8 +772,16 @@ static int applespi_send_cmd_msg(struct applespi_data *applespi)
 		return 0;
 
 	/* check whether send is in progress */
-	if (applespi->cmd_msg_queued)
-		return 0;
+	if (applespi->cmd_msg_queued) {
+		if (ktime_ms_delta(ktime_get(), applespi->cmd_msg_queued) < 1000)
+			return 0;
+
+		dev_warn(&applespi->spi->dev, "Command %d timed out\n",
+			 applespi->cmd_evt_type);
+
+		applespi->cmd_msg_queued = 0;
+		applespi->write_active = false;
+	}
 
 	/* set up packet */
 	memset(packet, 0, APPLESPI_PACKET_SIZE);
@@ -869,7 +878,7 @@ static int applespi_send_cmd_msg(struct applespi_data *applespi)
 		return sts;
 	}
 
-	applespi->cmd_msg_queued = true;
+	applespi->cmd_msg_queued = ktime_get();
 	applespi->write_active = true;
 
 	return 0;
@@ -1921,7 +1930,7 @@ static int __maybe_unused applespi_resume(struct device *dev)
 	applespi->drain = false;
 	applespi->have_cl_led_on = false;
 	applespi->have_bl_level = 0;
-	applespi->cmd_msg_queued = false;
+	applespi->cmd_msg_queued = 0;
 	applespi->read_active = false;
 	applespi->write_active = false;
 
-- 
2.26.2