On Wed, Aug 12, 2015 at 04:23:12PM +0300, Jani Nikula wrote:
On Wed, 12 Aug 2015, Daniel Vetter daniel@ffwll.ch wrote:
On Wed, Aug 12, 2015 at 09:20:17AM +0300, Jani Nikula wrote:
On Wed, 12 Aug 2015, "Yang, Libin" libin.yang@intel.com wrote:
Hi Jani,
-----Original Message----- From: Jani Nikula [mailto:jani.nikula@linux.intel.com] Sent: Tuesday, August 11, 2015 4:14 PM To: Yang, Libin; alsa-devel@alsa-project.org; tiwai@suse.de; intel- gfx@lists.freedesktop.org; daniel.vetter@ffwll.ch Subject: RE: [Intel-gfx] [PATCH v4 4/4] drm/i915: set proper N/CTS in modeset
On Tue, 11 Aug 2015, "Yang, Libin" libin.yang@intel.com wrote:
Hi Jani,
> -----Original Message----- > From: Jani Nikula [mailto:jani.nikula@linux.intel.com] > Sent: Tuesday, August 11, 2015 3:14 PM > To: Yang, Libin; alsa-devel@alsa-project.org; tiwai@suse.de; intel- > gfx@lists.freedesktop.org; daniel.vetter@ffwll.ch > Subject: RE: [Intel-gfx] [PATCH v4 4/4] drm/i915: set proper N/CTS in > modeset > > On Tue, 11 Aug 2015, "Yang, Libin" libin.yang@intel.com wrote: > > Hi Jani, > > > > Thanks for careful reviewing for all the patches, please > > see my comments. > > > >> -----Original Message----- > >> From: Jani Nikula [mailto:jani.nikula@linux.intel.com] > >> Sent: Monday, August 10, 2015 8:10 PM > >> To: Yang, Libin; alsa-devel@alsa-project.org; tiwai@suse.de; intel- > >> gfx@lists.freedesktop.org; daniel.vetter@ffwll.ch > >> Subject: Re: [Intel-gfx] [PATCH v4 4/4] drm/i915: set proper N/CTS
in
> >> modeset > >> > >> On Mon, 10 Aug 2015, libin.yang@intel.com wrote: > >> > From: Libin Yang libin.yang@intel.com > >> > > >> > When modeset occurs and the TMDS frequency is set to some > >> > speical value, the N/CTS need to be set manually if audio > >> > is playing. > >> > >> When modeset occurs, we disable everything, and then re-enable > >> everything, and notify the audio driver every step of the way. IIUC > >> there should be no audio playing across the modeset, and when
the
> >> modeset is complete and we've set the valid ELD, the audio driver > >> should > >> call the callback from the earlier patches to set the correct audio > >> rate. > >> > >> Why is this patch needed? Please enlighten me. > > > > Please image this scenario: when audio is playing, the gfx driver > > does the modeset. In this situation, after modeset, audio driver > > will do nothing and continue playing. And audio driver will not call > > set_ncts. > > Why does the audio driver not do anything here? Whenever there's
a
> modeset, the graphics driver will disable audio and invalidate the
ELD,
> which should cause an interrupt to notify the audio driver about > this. This is no different from a hot-unplug, in fact I can't see how > the audio driver could even detect whether there's been a hotplug
or
> not > when there's a codec disable/enable.
Yes, it will trigger an interrupt to audio driver when unplug and another interrupt for hotplug. But from audio driver, we will not stop the playing and resume the playing based on the hotplug or modeset. The audio is always playing during the hotplug/modeset.
But the whole display, and consequently ELD, might have changed during the hotplug, why do you assume you can just keep playing?! The display might even have changed from HDMI to DP or vice versa.
The eld info changing will not impact the audio playing. Actually, you can image the monitor as a digital speaker, just like the headphone to the analog audio. Unplug the speaker will not impact on the audio playing. Of course , there is a little difference, when monitor hotplug, in the interrupt, we may change the codec configuration dynamically.
And audio driver supply the mechanism to stop the audio playing when hotplug if the HW requires.
We've also been putting a lot of effort into not depending on previous state when enabling the outputs, for more reliability. We generally don't do partial changes, we disable everything and then enable again. And now you're suggesting we look at some register which for all we know may have been valid for some other display?
In the patch, it will not depend on previous state, I think. We read the register value which is based on the state after modeset.
Okay, let's have the patches cleaned up and see. It'll be easier and quicker to solicit more review on that than this expanding thread.
It sounds like we actually need to ping the audio side _before_ we do the
Do you mean "read _HSW_AUD_STR_DESC_*" by "ping the audio side" above?
No, I mean call into snd-hda-intel before we do the modeset to ask it for what it actually wants to have set up. At least it feels a bit like only reacting to a modeset after it's done leads to confusion. Or maybe we just need to update the register values we want at compute_time instead of doing rwm fun ...
Pure gut feeling comment, I didn't look into details ;-) -Daniel