From: Guenter Roeck <linux@roeck-us.net>
To: Marco Felsch <m.felsch@pengutronix.de>
Cc: support.opensource@diasemi.com, contact@stefanchrist.eu,
Adam.Thomson.Opensource@diasemi.com,
linux-watchdog@vger.kernel.org, kernel@pengutronix.de,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] watchdog: da9062: make restart handler atomic safe
Date: Wed, 15 Jan 2020 08:54:47 -0800 [thread overview]
Message-ID: <20200115165447.GA13912@roeck-us.net> (raw)
In-Reply-To: <20200115162307.7336-1-m.felsch@pengutronix.de>
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
>
next prev parent reply other threads:[~2020-01-15 16:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 16:23 [PATCH v2] watchdog: da9062: make restart handler atomic safe Marco Felsch
2020-01-15 16:54 ` Guenter Roeck [this message]
2020-01-16 7:23 ` Stefan Lengfeld
2020-01-19 11:34 ` Stefan Lengfeld
2020-01-23 15:03 ` Adam Thomson
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