[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 <[email protected]> wrote: >>> [AMD Official Use Only - Internal Distribution Only] >>> >>>On Wed, Sep 16, 2020 at 3:42 PM Qingqing Zhuo <[email protected]> wrote: >>>> From: jinlong zhang <[email protected]> >>>> >>> >[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 <[email protected]> >>>> Reviewed-by: Wenjing Liu <[email protected]> >>>> Acked-by: Qingqing Zhuo <[email protected]> >>>> --- >>>> 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 >>>> >>>> _______________________________________________ >>>> amd-gfx mailing list >>>> [email protected] >>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fli >>>> st >>>> s.freedesktop.org%2Fmailman%2Flistinfo%2Famd-gfx&data=02%7C01%7C >>>> qi >>>> ngqing.zhuo%40amd.com%7C36c3bee68c28448769fa08d85a884619%7C3dd8961fe >>>> 48 >>>> 84e608e11a82d994e183d%7C0%7C0%7C637358888627498307&sdata=mynpHpi >>>> up >>>> J%2FU2o5gZNW%2Bft%2Fg2beFY86%2BzMRWoTZCghQ%3D&reserved=0 >> _______________________________________________ >> amd-gfx mailing list >> [email protected] >> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flist >> s.freedesktop.org%2Fmailman%2Flistinfo%2Famd-gfx&data=02%7C01%7CQi >> ngqing.Zhuo%40amd.com%7Cd4acd0d5e65c49a7270f08d85ae37036%7C3dd8961fe48 >> 84e608e11a82d994e183d%7C0%7C0%7C637359280197936127&sdata=ahcoCqG91 >> EDMNlHNSk4Eimh1azMtRWSX%2BKyHCdpFq1Q%3D&reserved=0 _______________________________________________ amd-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/amd-gfx
