[PATCH 04/15] drm/amd/display: Replace msleep with udelay while read edid return defer.

[Zhuo, Qingqing]

[AMD Official Use Only - Internal Distribution Only]

On Wed, Sep 16, 2020 at 3:42 PM Qingqing Zhuo <qingqing.zhuo at amd.com> wrote:
>
> From: jinlong zhang <jinlong.zhang at amd.com>
>
> [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?  

Thank you,
Lillian


>
> Signed-off-by: jinlong zhang <jinlong.zhang at amd.com>
> Reviewed-by: Wenjing Liu <Wenjing.Liu at amd.com>
> Acked-by: Qingqing Zhuo <qingqing.zhuo at amd.com>
> ---
>  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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