lkml.org 
[lkml]   [2020]   [Jan]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] watchdog: da9062: make restart handler atomic safe
On Wed, Jan 15, 2020 at 05:23:07PM +0100, Marco Felsch wrote:
> 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") to address this use case. Using regmap within an atomic
> context is allowed only if the regmap type is MMIO and the cache type
> 'flat' or no cache is used. Using the i2c_smbus_write_byte_data()
> function can be done without additional tests because:
> 1) the DA9062 is an i2c-only device and
> 2) the i2c framework emulates the smbus protocol if the host adapter
> does not support smbus_xfer by using the master_xfer.
>
> Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> Hi,
>
> This patch is based on Stefan Lengfeld's RFC Patch [1].
>
> [1] https://patchwork.ozlabs.org/patch/1085942/
>
> Changes:
>
> v2:
> - adapt commit message
> - add comment
> - make use of i2c_smbus_write_byte_data()
> ---
> drivers/watchdog/da9062_wdt.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/watchdog/da9062_wdt.c b/drivers/watchdog/da9062_wdt.c
> index c9b9d6394525..77b6b5336067 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 +150,13 @@ 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);
> int ret;
>
> - ret = regmap_write(wdt->hw->regmap,
> - DA9062AA_CONTROL_F,
> - DA9062AA_SHUTDOWN_MASK);
> - if (ret)
> + /* Don't use regmap because it is not atomic safe */
> + ret = i2c_smbus_write_byte_data(client, DA9062AA_CONTROL_F,
> + DA9062AA_SHUTDOWN_MASK);
> + if (ret < 0)
> dev_alert(wdt->hw->dev, "Failed to shutdown (err = %d)\n",
> ret);
>
> --
> 2.20.1
>

\
 
 \ /
  Last update: 2020-01-15 17:55    [W:0.046 / U:3.344 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site