[AMD Official Use Only - Internal Distribution Only]
Hi Jinlong,
This is a public thread for upstream review purpose mainly. Let's sync internally for your issue.
Thanks,
Lillian
-----Original Message-----
From: Koenig, Christian <Christian.Koenig@xxxxxxx>
Sent: Thursday, September 17, 2020 10:46 AM
To: Zhang, Jinlong <Jinlong.Zhang@xxxxxxx>; Zhuo, Qingqing <Qingqing.Zhuo@xxxxxxx>; Alex Deucher <alexdeucher@xxxxxxxxx>
Cc: Brol, Eryk <Eryk.Brol@xxxxxxx>; Li, Sun peng (Leo) <Sunpeng.Li@xxxxxxx>; Lakha, Bhawanpreet <Bhawanpreet.Lakha@xxxxxxx>; Siqueira, Rodrigo <Rodrigo.Siqueira@xxxxxxx>; amd-gfx list <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>; Wentland, Harry <Harry.Wentland@xxxxxxx>
Subject: Re: [PATCH 04/15] drm/amd/display: Replace msleep with udelay while read edid return defer.
No idea what that is. I can include delay.h just fine in the rest of the driver.
Must be something DC specific.
Regards,
Christian.
Am 17.09.20 um 16:39 schrieb Zhang, Jinlong:
> HI Christian
> While #include <linux/delay.h>, it prompt
> ..\..\..\..\..\dc\dce\dce_aux.c(31): fatal error C1083: Cannot open
> include file: 'linux/delay.h': No such file or directory Could you
> help to check how to include the header of void usleep_range(unsigned
> long min, unsigned long max);
>
> -----Original Message-----
> From: Zhuo, Qingqing <Qingqing.Zhuo@xxxxxxx>
> Sent: Thursday, September 17, 2020 9:02 PM
> To: Koenig, Christian <Christian.Koenig@xxxxxxx>; Alex Deucher
> <alexdeucher@xxxxxxxxx>
> Cc: Brol, Eryk <Eryk.Brol@xxxxxxx>; Li, Sun peng (Leo)
> <Sunpeng.Li@xxxxxxx>; Lakha, Bhawanpreet <Bhawanpreet.Lakha@xxxxxxx>;
> Siqueira, Rodrigo <Rodrigo.Siqueira@xxxxxxx>; amd-gfx list
> <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>; Zhang, Jinlong
> <Jinlong.Zhang@xxxxxxx>; Wentland, Harry <Harry.Wentland@xxxxxxx>
> Subject: RE: [PATCH 04/15] drm/amd/display: Replace msleep with udelay while read edid return defer.
>
> [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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