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

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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().

--
With best wishes,
Vladimir



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