Re: [PATCH 1/2] gpio: omap: prepare and unprepare the debounce clock

[Javier Martinez Canillas <javier@xxxxxxxxxxxx>]

Hello Rajendra,

On Thu, May 8, 2014 at 1:10 PM, Rajendra Nayak <rnayak@xxxxxx> wrote:
> On Thursday 08 May 2014 02:56 PM, Javier Martinez Canillas wrote:
>> Hello Rajendra,
>>
>> On Thu, May 8, 2014 at 9:06 AM, Rajendra Nayak <rnayak@xxxxxx> wrote:
>>> On Wednesday 23 April 2014 11:41 AM, Rajendra Nayak wrote:
>>>> Replace the clk_enable()s with a clk_prepare_enable() and
>>>> the clk_disables()s with a clk_disable_unprepare()
>>>>
>>>> This never showed issues due to the OMAP platform code (hwmod)
>>>> leaving these clocks in clk_prepare()ed state by default.
>>>>
>>>> Reported-by: Kishon Vijay Abraham I <kishon@xxxxxx>
>>>> Signed-off-by: Rajendra Nayak <rnayak@xxxxxx>
>>>> Cc: linux-gpio@xxxxxxxxxxxxxxx
>>>> Cc: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
>>>> Cc: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>
>>>
>>> Linus,
>>>
>>> Do you mind picking this fix up via the GPIO tree? Alternatively you could
>>> Ack this if you are fine and we can take both Patch 1/2 and Patch 2/2 from this
>>> series via the OMAP tree.
>>>
>>> Patch 2/2 has a dependency on Patch 1/2 and they need to go in in that order else
>>> gpio would break. More discussions are here [1].
>>> Let us know what you think. Thanks.
>>>
>>
>> I wonder if that is really the case. Your Patch 2/2 removes the call
>> to clk_prepare on _init_opt_clks() but it also replaces
>> clk_{enable,disable} with clk_prepare_enable()/clk_disable_unprepare()
>> on _enable_optional_clocks() and _disable_optional_clocks()
>> respectively.
>
> Right, the difference being, by the time hwmod is done enabling/disabling
> the opt clocks, without patch 2/2, the prepare count is 1, with patch 2/2
> prepare count is 0.
>

Ok, got it now.

>>
>> And GPIO banks are reset by hwmod on init which as far as I know
>> happen very early before the GPIO OMAP driver is even probed so by the
>> time clk_enable() is called on the GPIO driver the clock will already
>> be prepared by _enable_optional_clocks(). I tested linux-gpio/devel
>
> and unprepared by _disable_optional_clocks()?
>

I see that _disable_optional_clocks() is called as well so the clock
is left unprepared as you said.

>> branch + only your Patch 2/2 and the GPIOs were working correctly on a
>> OMAP3 board.
>
> Did gpio_debounce() ever get called for any of the gpios?
>

I don't see gpio_debounce() to be called indeed.

omap_gpio_runtime_resume() is executed and calls
_gpio_dbck_enable(bank) but clk_enable(bank->dbck) is not called since
bank->dbck_enable_mask is 0, that was my confusion since I thought
that clk_enable() was called.

Now I understand the dependency between the two patches.

>>
>> So I think that there isn't a strict dependency between these two
>> patches or am I missing something?
>>
>> In fact now that I think about it I wonder what's the functional
>> change of your Patch 2/2 since hwmod is still calling clk_prepare()
>> before the driver. If the clocks should actually be controlled by the
>
> I don't understand why you say 'before the driver'. Hwmod needs to control
> optional clocks for some devices in order to do a ocp reset. So it does
> touch these optional clocks, but if you look at the code it subsequently
> also disables (and unprepares with patch 2/2) these clocks before returning
> the control to the driver.
>

Right, it was just me getting confused by the interaction between
hwmod and the GPIO driver. Thanks a lot for the explanation and sorry
for the noise.

Feel free to add my:

Acked-by: Javier Martinez Canillas <javier@xxxxxxxxxxxx>

Best regards,
Javier

>> drivers like you said then I think that we should remove
>> _{enable,disable}_optional_clocks() completely and let the drivers do
>> the clock prepare and enable like is made on your Patch 1/2 for the
>> GPIO driver.
>>
>> What do you think about it?
>>
>> Best regards,
>> Javier
>>
>>> regards,
>>> Rajendra
>>>
>>> [1] http://www.mail-archive.com/linux-gpio@xxxxxxxxxxxxxxx/msg02801.html
>>>
>>>> ---
>>>>  drivers/gpio/gpio-omap.c |   10 +++++-----
>>>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>> index 19b886c..78bc5a4 100644
>>>> --- a/drivers/gpio/gpio-omap.c
>>>> +++ b/drivers/gpio/gpio-omap.c
>>>> @@ -180,7 +180,7 @@ static inline void _gpio_rmw(void __iomem *base, u32 reg, u32 mask, bool set)
>>>>  static inline void _gpio_dbck_enable(struct gpio_bank *bank)
>>>>  {
>>>>       if (bank->dbck_enable_mask && !bank->dbck_enabled) {
>>>> -             clk_enable(bank->dbck);
>>>> +             clk_prepare_enable(bank->dbck);
>>>>               bank->dbck_enabled = true;
>>>>
>>>>               writel_relaxed(bank->dbck_enable_mask,
>>>> @@ -198,7 +198,7 @@ static inline void _gpio_dbck_disable(struct gpio_bank *bank)
>>>>                */
>>>>               writel_relaxed(0, bank->base + bank->regs->debounce_en);
>>>>
>>>> -             clk_disable(bank->dbck);
>>>> +             clk_disable_unprepare(bank->dbck);
>>>>               bank->dbck_enabled = false;
>>>>       }
>>>>  }
>>>> @@ -231,7 +231,7 @@ static void _set_gpio_debounce(struct gpio_bank *bank, unsigned gpio,
>>>>
>>>>       l = GPIO_BIT(bank, gpio);
>>>>
>>>> -     clk_enable(bank->dbck);
>>>> +     clk_prepare_enable(bank->dbck);
>>>>       reg = bank->base + bank->regs->debounce;
>>>>       writel_relaxed(debounce, reg);
>>>>
>>>> @@ -245,7 +245,7 @@ static void _set_gpio_debounce(struct gpio_bank *bank, unsigned gpio,
>>>>       bank->dbck_enable_mask = val;
>>>>
>>>>       writel_relaxed(val, reg);
>>>> -     clk_disable(bank->dbck);
>>>> +     clk_disable_unprepare(bank->dbck);
>>>>       /*
>>>>        * Enable debounce clock per module.
>>>>        * This call is mandatory because in omap_gpio_request() when
>>>> @@ -290,7 +290,7 @@ static void _clear_gpio_debounce(struct gpio_bank *bank, unsigned gpio)
>>>>               bank->context.debounce = 0;
>>>>               writel_relaxed(bank->context.debounce, bank->base +
>>>>                            bank->regs->debounce);
>>>> -             clk_disable(bank->dbck);
>>>> +             clk_disable_unprepare(bank->dbck);
>>>>               bank->dbck_enabled = false;
>>>>       }
>>>>  }
>>>>
>>>
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