2016-12-18 23:25:55

by Andrey Smirnov

Subject: [PATCH] at86rf230: Allow slow GPIO pins for "rstn"

Driver code never touches "rstn" signal in atomic context, so there's
no need to implicitly put such restriction on it by using gpio_set_value
to manipulate it. Replace gpio_set_value to gpio_set_value_cansleep to
fix that.

As a an example of where such restriction might be inconvenient,
consider a hardware design where "rstn" is connected to a pin of I2C/SPI
GPIO expander chip.

Cc: Chris Healy <[email protected]>
Signed-off-by: Andrey Smirnov <[email protected]>
---
drivers/net/ieee802154/at86rf230.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ieee802154/at86rf230.c b/drivers/net/ieee802154/at86rf230.c
index 9f10da6..7700690 100644
--- a/drivers/net/ieee802154/at86rf230.c
+++ b/drivers/net/ieee802154/at86rf230.c
@@ -1710,9 +1710,9 @@ static int at86rf230_probe(struct spi_device *spi)
/* Reset */
if (gpio_is_valid(rstn)) {
udelay(1);
- gpio_set_value(rstn, 0);
+ gpio_set_value_cansleep(rstn, 0);
udelay(1);
- gpio_set_value(rstn, 1);
+ gpio_set_value_cansleep(rstn, 1);
usleep_range(120, 240);
}

--
2.5.5

2016-12-21 12:31:09

by Nikita Yushchenko

Subject: Re: at86rf230: Allow slow GPIO pins for "rstn"

> Driver code never touches "rstn" signal in atomic context, so there's
> no need to implicitly put such restriction on it by using gpio_set_value
> to manipulate it. Replace gpio_set_value to gpio_set_value_cansleep to
> fix that.
>
> As a an example of where such restriction might be inconvenient,
> consider a hardware design where "rstn" is connected to a pin of I2C/SPI
> GPIO expander chip.
>
> Cc: Chris Healy <[email protected]>
> Signed-off-by: Andrey Smirnov <[email protected]>

Reviewed-by: Nikita Yushchenko <[email protected]>

2016-12-21 13:11:56

by Stefan Schmidt

Subject: Re: [PATCH] at86rf230: Allow slow GPIO pins for "rstn"

Hello.

On 19/12/16 00:25, Andrey Smirnov wrote:
> Driver code never touches "rstn" signal in atomic context, so there's
> no need to implicitly put such restriction on it by using gpio_set_value
> to manipulate it. Replace gpio_set_value to gpio_set_value_cansleep to
> fix that.

We need to make sure we are not assuming it can be called in such a
context in the future now. But that is something we can worry about if
it comes up.

> As a an example of where such restriction might be inconvenient,
> consider a hardware design where "rstn" is connected to a pin of I2C/SPI
> GPIO expander chip.

Is this a real life issue you run into?

> Cc: Chris Healy <[email protected]>
> Signed-off-by: Andrey Smirnov <[email protected]>
> ---
> drivers/net/ieee802154/at86rf230.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ieee802154/at86rf230.c b/drivers/net/ieee802154/at86rf230.c
> index 9f10da6..7700690 100644
> --- a/drivers/net/ieee802154/at86rf230.c
> +++ b/drivers/net/ieee802154/at86rf230.c
> @@ -1710,9 +1710,9 @@ static int at86rf230_probe(struct spi_device *spi)
> /* Reset */
> if (gpio_is_valid(rstn)) {
> udelay(1);
> - gpio_set_value(rstn, 0);
> + gpio_set_value_cansleep(rstn, 0);
> udelay(1);
> - gpio_set_value(rstn, 1);
> + gpio_set_value_cansleep(rstn, 1);
> usleep_range(120, 240);
> }
>
>


Acked-by: Stefan Schmidt <[email protected]>

regards
Stefan Schmidt

2016-12-21 21:01:23

by Stefan Schmidt

Subject: Re: [PATCH] at86rf230: Allow slow GPIO pins for "rstn"

Hello.

On 21/12/16 19:30, Chris Healy wrote:
>
>
> On Dec 21, 2016 5:11 AM, "Stefan Schmidt" <[email protected]
> <mailto:[email protected]>> wrote:
>
> Hello.
>
>
> On 19/12/16 00:25, Andrey Smirnov wrote:
>
> Driver code never touches "rstn" signal in atomic context, so
> there's
> no need to implicitly put such restriction on it by using
> gpio_set_value
> to manipulate it. Replace gpio_set_value to
> gpio_set_value_cansleep to
> fix that.
>
>
> We need to make sure we are not assuming it can be called in such a
> context in the future now. But that is something we can worry about
> if it comes up.
>
>
> As a an example of where such restriction might be inconvenient,
> consider a hardware design where "rstn" is connected to a pin of
> I2C/SPI
> GPIO expander chip.
>
>
> Is this a real life issue you run into?
>
>
> I have a platform with this configuration. The DTS for the platform is
> in the process of being mainlined right now.

Thanks for letting us know. What platform is that? I'm always interested
in hearing about devices that use the Linux ieee802154 subsystem. :)

regards
Stefan Schmidt