Re: [PATCH 1/2] PCI: rcar: Poll more often in rcar_pcie_wait_for_dl()

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On 03/19/2018 03:48 PM, Marek Vasut wrote:
> On 03/19/2018 02:43 PM, Vladimir Zapolskiy wrote:
>> On 03/19/2018 12:56 PM, Marek Vasut wrote:
>>> On 03/19/2018 11:53 AM, Geert Uytterhoeven wrote:
>>>> Hi Marek,
>>>>
>>>> On Mon, Mar 19, 2018 at 10:53 AM, Marek Vasut <marek.vasut@xxxxxxxxx> wrote:
>>>>> On 03/19/2018 09:38 AM, Simon Horman wrote:
>>>>>> On Sun, Mar 18, 2018 at 11:52:52AM +0100, Marek Vasut wrote:
>>>>>>> The data link active signal usually takes ~20 uSec to be asserted,
>>>>>>> poll the bit more often to avoid useless delays in this function.
>>>>>>>
>>>>>>> Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxx>
>>>>>>> Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>>>>>>> Cc: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
>>>>>>> Cc: Simon Horman <horms+renesas@xxxxxxxxxxxx>
>>>>>>> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
>>>>>>> Cc: linux-renesas-soc@xxxxxxxxxxxxxxx
>>>>>>
>>>>>> Unless my eyes deceive me this seems to be quite a lot (100x) more often,
>>>>>> but so be it.
>>>>>
>>>>> It's just a higher frequency to avoid slowdown when bringing the link up.
>>>>
>>>> No it isn't: you replaced a sleep by a delay, thus making it blocking.
>>>
>>> For much shorter period of time.
>>>
>>>> So this can spin for up to 50 ms (+ overhead)?
>>>
>>> That's what it did before too , it used msleep and now it uses udelay.
>>>
>>
>> msleep() does not spin, it reschedules the process.
>>
>> Instead to find a balance you may want to play with usleep_range().
> 
> Which does not work in atomic context, which will be needed when using
> this function in suspend/resume later on.
> 

IIRC suspend/resume are never executed in atomic context, and runtime
suspend/resume are invoked in atomic context only if pm_runtime_irq_safe()
is called (just a few drivers in vanilla uses it at the moment).

Nevertheless, the commit message does not say that the change is needed
for future suspend/resume add-on.

--
With best wishes,
Vladimir




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