linux-kernel - Re: [PATCH V4 4/4] pwm: tegra: Add support to configure pin state in suspends/resume

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Date:   Fri, 7 Apr 2017 08:51:54 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Laxman Dewangan <ldewangan@...dia.com>, <thierry.reding@...il.com>,
        <robh+dt@...nel.org>
CC:     <mark.rutland@....com>, <linux-pwm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 4/4] pwm: tegra: Add support to configure pin state in
 suspends/resume


On 06/04/17 17:40, Laxman Dewangan wrote:
> Oops, it was actually v2.
> 
> On Thursday 06 April 2017 08:47 PM, Jon Hunter wrote:
>> On 06/04/17 15:21, Laxman Dewangan wrote:
>>> In some of NVIDIA Tegra's platform, PWM controller is used to
>>> control the PWM controlled regulators. PWM signal is connected to
>>> the VID pin of the regulator where duty cycle of PWM signal decide
>>> the voltage level of the regulator output.
>>>
>>> The tristate (high impedance of PWM pin form Tegra) also define
>>> one of the state of PWM regulator which needs to be configure in
>>> suspend state of system.
>>>
>>> Add support to configure the pin state via pinctrl frameworks in
>>> suspend and active state of the system.
>>>
>>> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
>>> ---
>>> Changes from v1:
>>> - Use standard pinctrl names for sleep and active state.
>>> - Use API pinctrl_pm_select_*()
>>>
>>>   drivers/pwm/pwm-tegra.c | 22 ++++++++++++++++++++++
>>>   1 file changed, 22 insertions(+)
>>>
>>> diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c
>>> index e9c4de5..af1bd4f 100644
>>> --- a/drivers/pwm/pwm-tegra.c
>>> +++ b/drivers/pwm/pwm-tegra.c
>>> @@ -29,6 +29,7 @@
>>>   #include <linux/of_device.h>
>>>   #include <linux/pwm.h>
>>>   #include <linux/platform_device.h>
>>> +#include <linux/pinctrl/consumer.h>
>>>   #include <linux/slab.h>
>>>   #include <linux/reset.h>
>>>   @@ -256,6 +257,22 @@ static int tegra_pwm_remove(struct
>>> platform_device *pdev)
>>>       return pwmchip_remove(&pc->chip);
>>>   }
>>>   +#ifdef CONFIG_PM_SLEEP
>>> +static int tegra_pwm_suspend(struct device *dev)
>>> +{
>>> +    pinctrl_pm_select_sleep_state(dev);
>> Why not return the error code here?
> 
> As the pin state in suspend is optional, I dont  want to return error if
> the sleep state is not available.
> 
> However, it seems pinctrl take care of retuning success if there is no
> sleep state. By seeing code.

Exactly, that is what I did for i2c because pinctrl it is also optional
for i2c.

> Let me test this on different condition and it it works fine then we can
> return the return of pinctrl_pm_select_*()
> 
> 
> BTW, it should be OK to have pwm_tegra_resume/suspend wrapper, not
> directly use the pinctrl_pm_select_* in pm ops suspend/resume. The
> prototype matches.

I think that I would keep the wrapper.

>> By the way, do you plan to include patches to populate the bindings for
>> the pwm devices?
> 
> I am planning to populate the GPU regulator which is PWM based. This
> will only populate the regulator.

Ok.

Jon

-- 
nvpublic