linux-kernel - [PATCH] watchdog: da9062: make restart handler atomic safe

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Date:   Mon, 13 Jan 2020 10:15:21 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     support.opensource@...semi.com, linux@...ck-us.net,
        contact@...fanchrist.eu, Adam.Thomson.Opensource@...semi.com
Cc:     linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de
Subject: [PATCH] watchdog: da9062: make restart handler atomic safe

The restart handler is executed during the shutdown phase which is
atomic/irq-less. The i2c framework supports atomic transfers since
commit 63b96983a5dd ("i2c: core: introduce callbacks for atomic
transfers") but unfortunately the regmap framework doesn't support it
yet. Hard coding the i2c stuff can be done without worries since the
DA9062 is an i2c-only device.

Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
---
Hi,

This patch is based on Stefan Lengfeld's RFC Patch [1].

[1] https://patchwork.ozlabs.org/patch/1085942/
---
 drivers/watchdog/da9062_wdt.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/watchdog/da9062_wdt.c b/drivers/watchdog/da9062_wdt.c
index c9b9d6394525..84c5a0a455b2 100644
--- a/drivers/watchdog/da9062_wdt.c
+++ b/drivers/watchdog/da9062_wdt.c
@@ -11,6 +11,7 @@
 #include <linux/platform_device.h>
 #include <linux/uaccess.h>
 #include <linux/slab.h>
+#include <linux/i2c.h>
 #include <linux/delay.h>
 #include <linux/jiffies.h>
 #include <linux/mfd/da9062/registers.h>
@@ -149,12 +150,18 @@ static int da9062_wdt_restart(struct watchdog_device *wdd, unsigned long action,
 			      void *data)
 {
 	struct da9062_watchdog *wdt = watchdog_get_drvdata(wdd);
+	struct i2c_client *client = to_i2c_client(wdt->hw->dev);
+	u8 buf[] = {DA9062AA_CONTROL_F, DA9062AA_SHUTDOWN_MASK};
+	struct i2c_msg msg = {
+		.addr = client->addr,
+		.flags = 0,
+		.len = sizeof(buf),
+		.buf = buf,
+	};
 	int ret;
 
-	ret = regmap_write(wdt->hw->regmap,
-			   DA9062AA_CONTROL_F,
-			   DA9062AA_SHUTDOWN_MASK);
-	if (ret)
+	ret = i2c_transfer(client->adapter, &msg, 1);
+	if (ret < 0)
 		dev_alert(wdt->hw->dev, "Failed to shutdown (err = %d)\n",
 			  ret);
 
-- 
2.20.1