Re: [PATCH v5] drm/i915: pass ELD to HDMI/DP audio driver

[Takashi Iwai <tiwai@suse.de>]

At Thu, 10 Nov 2011 12:50:11 +0100,
Christopher White wrote:
> 
> On 11/10/11 12:22 PM, Takashi Iwai wrote:
> > At Thu, 10 Nov 2011 12:00:53 +0100,
> > Christopher White wrote:
> >> On 11/10/11 9:55 AM, Christopher White wrote:
> >>> On 11/10/11 8:55 AM, Wu Fengguang wrote:
> >>>> On Thu, Nov 10, 2011 at 03:33:50PM +0800, Wu Fengguang wrote:
> >>>>> Wow I reproduced the bug and got a very interesting dmesg:
> >>>>>
> >>>>> gfx =>          [ 4561.287980] [drm:intel_write_eld], ELD on
> >>>>> [CONNECTOR:12:HDMI-A-2], [ENCODER:11:TMDS-11]
> >>>>> gfx =>          [ 4561.291730] [drm:ironlake_write_eld], ELD on pipe B
> >>>>> gfx =>          [ 4561.293804] [drm:ironlake_write_eld], Audio
> >>>>> directed to unknown port
> >>>>> gfx =>          [ 4561.295273] [drm:ironlake_write_eld],
> >>>>>         alsa =>   [ 4561.295486] HDMI hot plug event: Codec=3 Pin=6
> >>>>> Presence_Detect=1 ELD_Valid=0
> >>>>>         alsa =>   [ 4561.295564] HDMI status: Codec=3 Pin=6
> >>>>> Presence_Detect=1 ELD_Valid=0
> >>>>> gfx =>          [ 4561.300020] ELD size 13
> >>>>>         alsa =>   [ 4561.300697] HDMI hot plug event: Codec=3 Pin=6
> >>>>> Presence_Detect=1 ELD_Valid=1
> >>>>>         alsa =>   [ 4561.303322] HDMI status: Codec=3 Pin=6
> >>>>> Presence_Detect=1 ELD_Valid=1
> >>>>>         alsa =>   [ 4561.311120] ALSA hda_eld.c:259 HDMI: Unknown ELD
> >>>>> version 0
> >>>>>
> >>>>> Hey the two parts are interleaved!
> >>>>>
> >>>>> But still it should work all fine, since the gfx driver does
> >>>>>
> >>>>>           set ELD_Valid = 0
> >>>>>           write ELD
> >>>>>           set ELD_Valid = 1
> >>>>>
> >>>>> So the audio driver would read the correct ELD unless the ELD content
> >>>>> and flag writes are somehow _reordered_ underneath. Or the ELD content
> >>>>> writes take some time to take effect?
> >>>> Just confirmed that adding 1s delay can fix it!
> >>>>
> >>>> New dmesg is:
> >>>>
> >>>> [   48.564923] [drm:drm_crtc_helper_set_mode], [ENCODER:11:TMDS-11]
> >>>> set [MODE:34:]
> >>>> [   48.567481] [drm:intel_hdmi_mode_set], Enabling HDMI audio on pipe B
> >>>> [   48.568975] [drm:intel_write_eld], ELD on [CONNECTOR:12:HDMI-A-2],
> >>>> [ENCODER:11:TMDS-11]
> >>>> [   48.571728] [drm:ironlake_write_eld], ELD on pipe B
> >>>> [   48.572882] [drm:ironlake_write_eld], Audio directed to unknown port
> >>>> [   48.575252] [drm:ironlake_write_eld],
> >>>> [   48.575400] HDMI hot plug event: Codec=3 Pin=6 Presence_Detect=1
> >>>> ELD_Valid=0
> >>>> [   48.575487] HDMI status: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=0
> >>>> [   48.580116] ELD size 13
> >>>> [   48.580795] HDMI hot plug event: Codec=3 Pin=6 Presence_Detect=1
> >>>> ELD_Valid=1
> >>>> [   48.583340] HDMI status: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=1
> >>>> [   48.632514] [drm:intel_wait_for_vblank], vblank wait timed out
> >>>> [   48.685322] [drm:intel_wait_for_vblank], vblank wait timed out
> >>>> [   48.687438] [drm:ironlake_update_wm], FIFO watermarks For pipe A -
> >>>> plane 5, cursor: 6
> >>>> [   48.687438] [drm:ironlake_update_wm], FIFO watermarks For pipe A -
> >>>> plane 5, cursor: 6
> >>>> [   48.690106] [drm:ironlake_update_wm], FIFO watermarks For pipe B -
> >>>> plane 42, cursor: 6
> >>>> [   48.745204] [drm:intel_wait_for_vblank], vblank wait timed out
> >>>> [   48.798035] [drm:intel_wait_for_vblank], vblank wait timed out
> >>>> [   48.799633] [drm:ironlake_fdi_link_train], FDI_RX_IIR 0x100
> >>>> [   48.802686] [drm:ironlake_fdi_link_train], FDI train 1 done.
> >>>> [   48.805103] [drm:ironlake_fdi_link_train], FDI_RX_IIR 0x600
> >>>> [   48.807246] [drm:ironlake_fdi_link_train], FDI train 2 done.
> >>>> [   48.809426] [drm:ironlake_fdi_link_train], FDI train done
> >>>> [   48.813960] [drm:intel_update_fbc],
> >>>> [   48.814782] [drm:drm_crtc_helper_set_config], Setting connector
> >>>> DPMS state to on
> >>>> [   48.818093] [drm:drm_crtc_helper_set_config],
> >>>> [CONNECTOR:12:HDMI-A-2] set DPMS on
> >>>> [   48.828633] [drm:intel_prepare_page_flip], preparing flip with no
> >>>> unpin work?
> >>>> [   49.618962] HDMI: detected monitor RX-V1800 at connection type HDMI
> >>>> [   49.621013] HDMI: available speakers: FL/FR LFE FC RL/RR RC RLC/RRC
> >>>> [   49.622304] HDMI: supports coding type LPCM: channels = 2, rates =
> >>>> 32000 44100 48000 96000 176400 192000 384000, bits = 16 20 24
> >>>> [   49.625069] HDMI: supports coding type LPCM: channels = 8, rates =
> >>>> 32000 44100 48000 96000 176400 192000 384000, bits = 16 20 24
> >>>> [   49.628535] HDMI: supports coding type AC-3: channels = 6, rates =
> >>>> 32000 44100 48000, max bitrate = 640000
> >>>> [   49.630810] HDMI: supports coding type DTS: channels = 7, rates =
> >>>> 32000 44100 48000 96000 176400, max bitrate = 1536000
> >>>> [   49.633148] HDMI: supports coding type DSD (One Bit Audio):
> >>>> channels = 6, rates = 44100
> >>>> [   49.635039] HDMI: supports coding type E-AC-3/DD+ (Dolby Digital
> >>>> Plus): channels = 8, rates = 44100 48000
> >>>> [   49.637130] HDMI: supports coding type MLP (Dolby TrueHD):
> >>>> channels = 8, rates = 48000 176400 384000
> >>>> [   49.639172] HDMI: supports coding type DTS-HD: channels = 8, rates
> >>>> = 48000 176400 384000
> >>>>
> >>>> Thanks,
> >>>> Fengguang
> >>> Wow, you were able to reproduce it! That's the best news ever. I will
> >>> be applying this patch and rebuilding now to see what happens. So it
> >>> was some sort of timing issue after all.
> >>>
> >>> Expect me to reply within 1h, but rebuild takes some time.
> >> I still had the old build directory and only had to rebuild one module
> >> which only took 5 minutes. The rest of the delay was me doing an hour of
> >> tests as well as being on a 45 minute phone call. Anyway, now the result:
> >>
> >> Success!
> >>
> >> So we know it's a timing issue somewhere. Wow, real progress and near a
> >> solution. Finally! The big question now is what causes the audio driver
> >> to read the ELD while it is empty, and why the 1 second delay fixes it.
> >>
> >> Look at speakertest.txt here. It's beautiful. ;-) Playing digital
> >> multichannel sound over the HDMI PCH bus, and I can hear every channel
> >> in their proper location on my speaker system. It's beautiful. I've
> >> waited for this moment since building this Linux HTPC back in April. ;-)
> >> (I'm an astonishingly patient man hehe).
> >>
> >> Now as for why we needed a 1 second delay, any ideas? Could it be that
> >> the audio driver was reading the ELD while it wasn't written to the
> >> register yet?
> > Maybe not necessarily 1 second.  It could do some loop with a small
> > delay until it reads zero-size?  Or if it really can take long time
> > like 1 second, it'd be better to be a work to self-reschdule to do in
> > background, as it's called at the probing time and at each unsol
> > event.  Since radeon sends really zero-byte ELD when a DVI monitor
> > without audio is connected, stalling one second there is no good
> > choice.
> >
> > Hopefully this delay would fix the zero-size problem we are currently
> > working around in an ugly way (the comment mentions about ASUS P5E-VM
> > HDMI board), too.
> >
> >
> > thanks,
> >
> > Takashi
> 
> Well yes obviously the 1 second delay is a temporary workaround until 
> the real cause is found. Something like what you suggested should be the 
> final fix; a real loop that proceeds only when the data is ready (with a 
> 1 second or so maximum loop time, to avoid infinite loop if data never 
> becomes ready).
> 
> I don't think a background schedule would work, because the data needs 
> to be available at boot BEFORE the audio layer loads. Otherwise ALSA 
> (for example) would load while no data had yet been read into the ELD 
> registers. If a background schedule is used, then GREAT care must be 
> taken to make sure it finishes before the audio layer launches.

In theory, the delayed probe and notification can be handled just like
a hotplug case.  We have still no notification framework (especially
in PulseAudio) yet, though :)


thanks,

Takashi