serial: imx: Avoid probe failure in case of missing gpiolib
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Message ID 20190801081524.22577-1-frieder.schrempf@kontron.de
State New
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Series
  • serial: imx: Avoid probe failure in case of missing gpiolib
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Commit Message

Schrempf Frieder Aug. 1, 2019, 8:18 a.m. UTC
From: Frieder Schrempf <frieder.schrempf@kontron.de>

If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() will return
-ENOSYS and cause the probing of the imx UART to fail. As the
GPIOs are optional, we should continue probing in this case.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
---
 drivers/tty/serial/imx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Uwe Kleine-König Aug. 1, 2019, 8:48 a.m. UTC | #1
On Thu, Aug 01, 2019 at 08:18:05AM +0000, Schrempf Frieder wrote:
> From: Frieder Schrempf <frieder.schrempf@kontron.de>
> 
> If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() will return
> -ENOSYS and cause the probing of the imx UART to fail. As the
> GPIOs are optional, we should continue probing in this case.

Is this really still the case? On which version did you hit this
problem?

I would expect that is gone with
d99482673f950817b30caf3fcdfb31179b050ce1 if not earlier.

Best regards
Uwe
Schrempf Frieder Aug. 1, 2019, 9:28 a.m. UTC | #2
Hi Uwe,

On 01.08.19 10:48, Uwe Kleine-König wrote:
> On Thu, Aug 01, 2019 at 08:18:05AM +0000, Schrempf Frieder wrote:
>> From: Frieder Schrempf <frieder.schrempf@kontron.de>
>>
>> If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() will return
>> -ENOSYS and cause the probing of the imx UART to fail. As the
>> GPIOs are optional, we should continue probing in this case.
> 
> Is this really still the case? On which version did you hit this
> problem?

Yes, I think it is. I used v5.2.5, that already has d99482673f95.

> 
> I would expect that is gone with
> d99482673f950817b30caf3fcdfb31179b050ce1 if not earlier.

I think this is a different problem. If CONFIG_GPIOLIB is disabled, 
mctrl_gpio_init() returns -ENOSYS unconditionally here: [1]. The 
existing patch (d99482673f95) seems to handle the case when 
CONFIG_GPIOLIB is enabled, but no or not all GPIOs are given in the dtb.

The sh-sci.c driver has a similar check to skip this case: [2].

Regards,
Frieder

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/serial_mctrl_gpio.h#n121
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/sh-sci.c#n3290
Uwe Kleine-König Aug. 1, 2019, 9:55 a.m. UTC | #3
On Thu, Aug 01, 2019 at 09:28:33AM +0000, Schrempf Frieder wrote:
> Hi Uwe,
> 
> On 01.08.19 10:48, Uwe Kleine-König wrote:
> > On Thu, Aug 01, 2019 at 08:18:05AM +0000, Schrempf Frieder wrote:
> >> From: Frieder Schrempf <frieder.schrempf@kontron.de>
> >>
> >> If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() will return
> >> -ENOSYS and cause the probing of the imx UART to fail. As the
> >> GPIOs are optional, we should continue probing in this case.
> > 
> > Is this really still the case? On which version did you hit this
> > problem?
> 
> Yes, I think it is. I used v5.2.5, that already has d99482673f95.
> 
> > 
> > I would expect that is gone with
> > d99482673f950817b30caf3fcdfb31179b050ce1 if not earlier.
> 
> I think this is a different problem. If CONFIG_GPIOLIB is disabled, 
> mctrl_gpio_init() returns -ENOSYS unconditionally here: [1]. The 
> existing patch (d99482673f95) seems to handle the case when 
> CONFIG_GPIOLIB is enabled, but no or not all GPIOs are given in the dtb.

Ah, I see.

I don't think we should handle this on a per-driver basis. So my
suggestion is to drop the dummy implementation for mctrl_gpio if GPIOLIB
is disabled. Then the behaviour should be consistant with the gpio stuff
returning NULL in this case. (Or alternatively adapt the dummy
implementation to shortcut and behave identically.)

(Having said that I don't like gpiolib's behaviour of returning NULL for
the optional calls if it's disabled, but having mctrl_gpio behave
differently is worse.)

> The sh-sci.c driver has a similar check to skip this case: [2].

This should than be dropped, too.

Best regards
Uwe

> [1] 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/serial_mctrl_gpio.h#n121
> [2] 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/sh-sci.c#n3290
Schrempf Frieder Aug. 1, 2019, 10:59 a.m. UTC | #4
On 01.08.19 11:55, Uwe Kleine-König wrote:
> On Thu, Aug 01, 2019 at 09:28:33AM +0000, Schrempf Frieder wrote:
>> Hi Uwe,
>>
>> On 01.08.19 10:48, Uwe Kleine-König wrote:
>>> On Thu, Aug 01, 2019 at 08:18:05AM +0000, Schrempf Frieder wrote:
>>>> From: Frieder Schrempf <frieder.schrempf@kontron.de>
>>>>
>>>> If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() will return
>>>> -ENOSYS and cause the probing of the imx UART to fail. As the
>>>> GPIOs are optional, we should continue probing in this case.
>>>
>>> Is this really still the case? On which version did you hit this
>>> problem?
>>
>> Yes, I think it is. I used v5.2.5, that already has d99482673f95.
>>
>>>
>>> I would expect that is gone with
>>> d99482673f950817b30caf3fcdfb31179b050ce1 if not earlier.
>>
>> I think this is a different problem. If CONFIG_GPIOLIB is disabled,
>> mctrl_gpio_init() returns -ENOSYS unconditionally here: [1]. The
>> existing patch (d99482673f95) seems to handle the case when
>> CONFIG_GPIOLIB is enabled, but no or not all GPIOs are given in the dtb.
> 
> Ah, I see.
> 
> I don't think we should handle this on a per-driver basis. So my
> suggestion is to drop the dummy implementation for mctrl_gpio if GPIOLIB
> is disabled. Then the behaviour should be consistant with the gpio stuff
> returning NULL in this case. (Or alternatively adapt the dummy
> implementation to shortcut and behave identically.)

I get your point, but it seems a bit strange to go down all the way from 
the driver to mctrl_gpio_init_noauto() and into the loop just to return 
an empty struct mctrl_gpios to the driver that will be looped over again 
on each call of mctrl_gpio_*().

So I would rather go with a variation of your second proposal and keep 
the dummy implementation, but let it return NULL instead of an error 
pointer, as all the mctrl_gpio_*() functions already seem to have a 
check for gpios == NULL.

What do you think?

> 
> (Having said that I don't like gpiolib's behaviour of returning NULL for
> the optional calls if it's disabled, but having mctrl_gpio behave
> differently is worse.)
> 
>> The sh-sci.c driver has a similar check to skip this case: [2].
> 
> This should than be dropped, too.
> 
> Best regards
> Uwe
> 
>> [1]
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/serial_mctrl_gpio.h#n121
>> [2]
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/sh-sci.c#n3290
>
Uwe Kleine-König Aug. 1, 2019, 11:50 a.m. UTC | #5
Hello,

On Thu, Aug 01, 2019 at 10:59:54AM +0000, Schrempf Frieder wrote:
> So I would rather go with a variation of your second proposal and keep 
> the dummy implementation, but let it return NULL instead of an error 
> pointer, as all the mctrl_gpio_*() functions already seem to have a 
> check for gpios == NULL.
> 
> What do you think?

I'll gladly review a patch.

Best regads
Uwe

Patch
diff mbox series

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 10db3e54ac9e..51714498dacf 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2237,7 +2237,9 @@  static int imx_uart_probe(struct platform_device *pdev)
 	timer_setup(&sport->timer, imx_uart_timeout, 0);
 
 	sport->gpios = mctrl_gpio_init(&sport->port, 0);
-	if (IS_ERR(sport->gpios))
+	if (PTR_ERR(sport->gpios) == -ENOSYS)
+		sport->gpios = NULL;
+	else if (IS_ERR(sport->gpios))
 		return PTR_ERR(sport->gpios);
 
 	sport->clk_ipg = devm_clk_get(&pdev->dev, "ipg");