[AMD Official Use Only - Internal Distribution Only]
Am 17.09.20 um 00:18 schrieb Alex Deucher:
>> On Wed, Sep 16, 2020 at 6:16 PM Zhuo, Qingqing <Qingqing.Zhuo@xxxxxxx> wrote:
>>> [AMD Official Use Only - Internal Distribution Only]
>>>
>>>On Wed, Sep 16, 2020 at 3:42 PM Qingqing Zhuo <qingqing.zhuo@xxxxxxx> wrote:
>>>> From: jinlong zhang <jinlong.zhang@xxxxxxx>
>>>>
>>> >[why]
>>>>while read edid return defer, then it enter to msleep, but it
>>>>actually took more time during msleep, this will cause remaining
>>>>edid read fail.
>>>>
>>>> [how]
>>>> Replacing msleep with udelay, it will not take any extra time, edid return pass finally.
>>> How long of a delay are we talking about here? Some platforms don't support long udelays and someone will send a patch to change this to msleep.
>>>
>>> Alex
>>>
>>> ---------------------
>>>
>>> Hi Alex,
>>>
>>> It's between 0-5ms for generic cases, though there exist some dongle workaround cases where we will do 70ms. Would this be a concern?
>> I think ARM has a limit of 2ms for udelay.
> Yeah, there is even a define somewhere for this.
> If you need a delay which is longer than this but still more precise than msleep() then there is the high precision timer sleep as alternative.
> I've forgotten the function name to use here, but there was a LWN article about this a few years ago. You just need to google a bit.
Hi Alex and Christian,
Thanks a lot for the input! Given what's been discussed, I will drop this patch for now.
Regards,
Lillian
>
> Regards,
> Christian.
>>
>> Alex
>>
>>> Thank you,
>>> Lillian
>>>
>>>
>>>> Signed-off-by: jinlong zhang <jinlong.zhang@xxxxxxx>
>>>> Reviewed-by: Wenjing Liu <Wenjing.Liu@xxxxxxx>
>>>> Acked-by: Qingqing Zhuo <qingqing.zhuo@xxxxxxx>
>>>> ---
>>>> drivers/gpu/drm/amd/display/dc/dce/dce_aux.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
>>>> b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
>>>> index 743042d5905a..cdcad82765e0 100644
>>>> --- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
>>>> +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
>>>> @@ -653,7 +653,7 @@ bool dce_aux_transfer_with_retries(struct ddc_service *ddc,
>>>> if ((*payload->reply == AUX_TRANSACTION_REPLY_AUX_DEFER) ||
>>>> (*payload->reply == AUX_TRANSACTION_REPLY_I2C_OVER_AUX_DEFER)) {
>>>> if (payload->defer_delay > 0)
>>>> - msleep(payload->defer_delay);
>>>> +
>>>> + udelay(payload->defer_delay * 1000);
>>>> }
>>>> }
>>>> break;
>>>> --
>>>> 2.17.1
>>>>
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