On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@xxxxxxxxxxxx> wrote: > > Hi, > > On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote: > > > > + sankeerth > > > > Hi Doug > > > > On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > > The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > > board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > > mode is listed first and thus is marked preferred. The EDID decode I > > > ran says: > > > > > > First detailed timing includes the native pixel format and preferred > > > refresh rate. > > > > > > ... > > > > > > Detailed Timing Descriptors: > > > DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > > Hfront 48 Hsync 32 Hback 80 Hpol N > > > Vfront 3 Vsync 5 Vback 69 Vpol N > > > DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > > Hfront 48 Hsync 32 Hback 80 Hpol N > > > Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > > I'm proposing here that the above is actually a bug and that the 60 Hz > > > mode really should be considered preferred by Linux. > > > > > > The argument here is that this is a laptop panel and on a laptop we > > > know power will always be a concern. Presumably even if someone using > > > this panel wanted to use 144 Hz for some use cases they would only do > > > so dynamically and would still want the default to be 60 Hz. > > > > > > Let's change the default to 60 Hz using a standard quirk. > > > > > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > > > > Yes, we were aware that 144Hz was getting picked. We found that while > > debugging the screen corruption issue. > > > > Well, yes power would be less with 60Hz but so will be the performance. > > What performance specifically will be less with 60 Hz? In general the > sc7280 CPU is a bit memory-bandwidth constrained and the LCD refresh > from memory is a non-trivial part of that. Reducing to 60 Hz will > relieve some of the memory bandwidth pressure and will actually allow > tasks on the CPU to run _faster_. I guess the downside is that some > animations might be a little less smooth... I guess he is referring to something that is vblank sync'd running faster than 60fps. but OTOH it is a bit of a waste for fbcon to be using 144Hz. And there are enough android games that limit themselves to 30fps to save your "phone" battery. So it seems a lot more sane to default to 60Hz and let userspace that knows it wants more pick the 144Hz rate when needed. BR, -R > > > > The test teams have been validating with 144Hz so far so we are checking > > internally with the team whether its OKAY to goto 60Hz now since that > > kind of invalidates the testing they have been doing. > > You're worried that the panel itself won't work well at 60 Hz, or > something else about the system won't? The whole system in general > needs to work well with 60 Hz displays and I expect them to be much > more common than 144 Hz displays. Quite honestly if switching to 60 Hz > uncovers a problem that would be a huge benefit of landing this patch > because it would mean we'd find it now rather than down the road when > someone hooks up a different panel. > > -Doug
