-----Original Message----- From: Jani Nikula [mailto:jani.nikula@xxxxxxxxxxxxxxx] Sent: Monday, May 29, 2017 4:29 PM To: Wang, Quanxian <quanxian.wang@xxxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx Cc: Yang, Libin <libin.yang@xxxxxxxxx> Subject: RE: [PATCH] Defined NM doesn't work on KBL and uses automatic N/M. On Fri, 26 May 2017, "Wang, Quanxian" <quanxian.wang@xxxxxxxxx> wrote: > "The patch is probably fine. But I can't invent an explanation if I > don't know what the problem is." > > @Jani @libin, is it possible for you to help contact Intel graphics > hardware design engineer to get the reason why M/N doesn't work as you > implemented in kernel code in Kabylake platform? I don't find good > reason in bspec. Thanks. How did you come up with the patch then? What made you try this? [Wang, Quanxian] I am from OSV enabling team and responsible for Ubuntu enabling. 17.04 (kernel 4.10) is released, we will do full testing for all Intel platforms including KBL/SKL... With audio testing, we found this regression issue on KBL and find patch caused this regression. Compared with previous implementation, we use automatic M/N to have a try. It works. BR, Jani. > > -----Original Message----- > From: Jani Nikula [mailto:jani.nikula@xxxxxxxxxxxxxxx] > Sent: Friday, May 26, 2017 7:01 PM > To: Wang, Quanxian <quanxian.wang@xxxxxxxxx>; > intel-gfx@xxxxxxxxxxxxxxxxxxxxx > Cc: Yang, Libin <libin.yang@xxxxxxxxx> > Subject: RE: [PATCH] Defined NM doesn't work on KBL and uses automatic N/M. > > On Fri, 26 May 2017, "Wang, Quanxian" <quanxian.wang@xxxxxxxxx> wrote: >> [Wang, Quanxian] in Ubuntu 17.04, we do audio testing on KBL/SKL/APL >> and more, the audio doesn't work on KBL specially, and other platform >> works fine. Even if with latest upstream kernel, but it works on 4.8 >> kernel. Therefore It is a regression issue. After investigation, we >> found it is caused by commit >> "6014ac122ed081feca99217bc57b2e15c7fc1a51] drm/i915/audio: set proper >> N/M in modeset". Therefore I provided this patch. > > If it's a regression, we need to backport the fix to stable kernels, and the patch needs annotation: > > Fixes: 6014ac122ed0 ("drm/i915/audio: set proper N/M in modeset") > Cc: <stable@xxxxxxxxxxxxxxx> # v4.10+ > >> After getting suggestion from you and Libin, we do more testing on 4K >> monitor for audio delay issue. Also talked with Libin why not use >> transcoder disable/enable process described in bspec, it will affect >> performance. >> >> This is the whole story. You can check LCK number 3791 in Intel JIRA >> about that. > > Actually, I can't. And the commit message needs to have the explanation. I still do not know what the bug is specifically, or why Kabylake, and only Kabylake, needs this. > >> [Wang, Quanxian] Basically if upstream could provide a reasonable >> patch, it will appreciate since you are expert in this area. >> Thanks for your understanding. > > The patch is probably fine. But I can't invent an explanation if I don't know what the problem is. > > > BR, > Jani. > > -- > Jani Nikula, Intel Open Source Technology Center -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
