Hi, Jani Thanks for your comment. My comment below. -----Original Message----- From: Jani Nikula [mailto:jani.nikula@xxxxxxxxxxxxxxx] Sent: Friday, May 26, 2017 4:31 PM To: Wang, Quanxian <quanxian.wang@xxxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx Cc: Yang, Libin <libin.yang@xxxxxxxxx>; Wang, Quanxian <quanxian.wang@xxxxxxxxx> Subject: Re: [PATCH] Defined NM doesn't work on KBL and uses automatic N/M. On Fri, 26 May 2017, Quanxian Wang <quanxian.wang@xxxxxxxxx> wrote: > According to the bspec, when set N/M, should disable and enable > transcoder which attaching DP audio. However with that implementation > will affect performance more. > > But with current implementation, KBL could not work with defined N/M. > By default, KBL will use automatic N/M. > > Signed-off-by: Quanxian Wang <quanxian.wang@xxxxxxxxx> > Reviewed-by: Libin Yang <libin.yang@xxxxxxxxx> > Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx> I have *NOT* reviewed this patch. Even if it's based on my suggestion in [1], it does not automatically signify review. [Wang, Quanxian] Sorry, I accept your suggestion. So in order to respect what you said, I input your name here. The patch subject should start with "drm/i915/audio:". [Wang, Quanxian] Ok. The DP spec always expresses the values as M/N, more specifically Maud/Naud, so it's confusing to see them expressed as N/M. [Wang, Quanxian] accept it. I still have trouble understanding the commit message. I am wondering if something was fixed in Kabylake and beyond, since according to [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. 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. 6014ac122ed0 ("drm/i915/audio: set proper N/M in modeset") we need this for certain modes. In particular, should the condition check for KBL || gen >= 10? [Wang, Quanxian] Basically if upstream could provide a reasonable patch, it will appreciate since you are expert in this area. Thanks for your understanding. BR, Jani. [1] http://mid.mail-archive.com/87pogs1lz7.fsf@xxxxxxxxx > --- > drivers/gpu/drm/i915/intel_audio.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_audio.c > b/drivers/gpu/drm/i915/intel_audio.c > index d805b6e..ba4994e 100644 > --- a/drivers/gpu/drm/i915/intel_audio.c > +++ b/drivers/gpu/drm/i915/intel_audio.c > @@ -289,6 +289,10 @@ hsw_dp_audio_config_update(struct intel_crtc *intel_crtc, enum port port, > enum pipe pipe = intel_crtc->pipe; > u32 tmp; > > + /* It doesn't work on KBL and uses automatic N/M. */ > + if (IS_KABYLAKE(dev_priv)) > + nm = NULL; > + > if (nm) > DRM_DEBUG_KMS("using Maud %u, Naud %u\n", nm->m, nm->n); > else -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
