Re: [PATCH] drm/amd/display: Use msleep instead of udelay for 8ms wait
From: Koenig, Christian
Date: Tue Jun 25 2019 - 10:27:01 EST
Am 25.06.19 um 16:12 schrieb Lucas Stach:
> Hi Harry,
> Am Dienstag, den 25.06.2019, 10:00 -0400 schrieb Harry Wentland:
>> arm32's udelay only allows values up to 2000 microseconds. msleep
>> does the trick for us here as there is no problem if this isn't
>> microsecond accurate and takes a tad longer.
> A "tad" longer in this case means likely double the intended wait.
> Please see "SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms)" in
Oh, thanks so much for the link! I was searching desperately for this
the last time this came up and couldn't find it.
Clearly going to remember now where to find that.
> The sleep here should use usleep_range. In general the DC code seems to
> use quite a lot of the udelay busy waits. I doubt that many of those
> occurrences are in atomic context, so could easily use a sleeping wait.
> Digging further this seems to apply across amdgpu, not only DC.
>> Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
>> Âdrivers/gpu/drm/amd/display/dc/core/dc_link.c | 2 +-
>> Â1 file changed, 1 insertion(+), 1 deletion(-)
>> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
>> index 4c31930f1cdf..f5d02f89b3f9 100644
>> --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
>> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
>> @@ -548,7 +548,7 @@ static void
>> read_edp_current_link_settings_on_detect(struct dc_link *link)
>> Â break;
>> Â }
>> - udelay(8000);
>> + msleep(8);
>> Â }
>> Â ASSERT(status == DC_OK);