On 09.09.24 5:00 AM, Peng Fan wrote: >> 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. With "downstream kernel" I didn't mean linux-imx. I meant our Kontron linux-ktn, which is based on mainline. I didn't test linux-imx to see if the issue occurs there, but that might be one task for further debugging.
