| Message ID | 20190625140046.31682-1-harry.wentland@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/amd/display: Use msleep instead of udelay for 8ms wait | expand |
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
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 Documentation/timers/timers-howto.txt. 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. Regards, Lucas > Signed-off-by: Harry Wentland <harry.wentland@amd.com> > --- > drivers/gpu/drm/amd/display/dc/core/dc_link.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c > b/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) > break; > } > > - udelay(8000); > + msleep(8); > } > > ASSERT(status == DC_OK);
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 > Documentation/timers/timers-howto.txt. 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. Thanks, Christian. > > 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. > > Regards, > Lucas > >> Signed-off-by: Harry Wentland <harry.wentland@amd.com> >> --- >> drivers/gpu/drm/amd/display/dc/core/dc_link.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c >> b/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) >> break; >> } >> >> - udelay(8000); >> + msleep(8); >> } >> >> ASSERT(status == DC_OK);
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/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) break; } - udelay(8000); + msleep(8); } ASSERT(status == DC_OK);
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. Signed-off-by: Harry Wentland <harry.wentland@amd.com> --- drivers/gpu/drm/amd/display/dc/core/dc_link.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)