> Subject: Re: i.MX8MP IMX-LCDIF Underrun Question(s) > > On 06.09.24 3:46 AM, Adam Ford wrote: > > I have been testing various settings on the HDMI out of the i.MX8MP. > > > > I noticed that sometimes my monitor would not sync, but sometimes > it > > would on the same resolution/refresh rate. Frieder noted the LCDIF > > was sometimes underflowing, so read up on it a little bit. > > > > In the comments of the LCDIF driver, it's noted: > > Set FIFO Panic watermarks, low 1/3, high 2/3 . > > > > However, in the downstream kernels, NXP changes the threshold to > 1/2 > > and 3/4 on the LCDIF that drives the HDMI, while leaving the other > > LCDIF interfaces at the default. > > > > When I increased the threshold to 1/2 and 3/4, it appeared that > > several resolutions that my monitor was struggling to sync started > > working, and it appeared to sync faster. I don't have an HDMI > > analyzer, so I cannot verify much beyond knowing if my monitor can > or > > cannot sync. > > For me this change doesn't seem to cause any improved behavior. My > monitor still fails to sync every few times I run "modetest -s" . > > Also we have a downstream kernel based on 6.1 with backported > HDMI support and I don't see the issues there. But I need to make > some further tests to make any reliable statements. > Downstream kernel has some NOC settings that not supported in upstream kernel, that maybe the issue. If you check 6.6 kernel, you could see some noc related settings in imx8mp-blk-ctl.c imx8m-blk-ctl.c and gpcv2.c. You may give a try with those noc settings applied and see whether that would improve. Regards, Peng. > > > > Could the threshold and underrun cause this monitor intermittent > > issue, or would this be something else? > > > > Does it make sense to have a flag or device tree option to override > > the default thresholds to change the panic level? > > > > adam
