[Intel-gfx] [alsa-devel] [PATCH 2/2] hda - delayed ELD repoll

[Wu Fengguang]

On Wed, Nov 16, 2011 at 02:25:00AM +0800, Stephen Warren wrote:
> Wu Fengguang wrote at Tuesday, November 15, 2011 7:33 AM:
> > The Intel HDMI chips (ironlake at least) are found to have ~250ms delay
> > between the ELD_Valid=1 hotplug event is send and the ELD buffer becomes
> > actually readable. During the time the ELD buffer is mysteriously all 0.
> > 
> > Fix it by scheduling a delayed work to re-read ELD buffer after 300ms.
> 
> Any idea why; is the graphics driver writing the ELD data to the audio HW
> after triggering the unsolicited even rather than before, or something
> like that?

Nope. The graphics driver is doing

        eld_valid = 0
        write to eld buffer
        eld_valid = 1

> 250mS almost sounds like it's setting ELDV in the audio HW,
> then going and reading the EDID, then writing the EDID to the audio HW;
> perhaps the graphics driver is accidentally setting PRESENT+ELDV when it's
> meant to be setting just PRESENT, and later setting ELDV?

>From the debug dmesg, I'm pretty sure that the ELDV events are
triggered exactly by the "eld_valid = 0" and "eld_valid = 1" register
writes. Since the ELD data is already prepared, there is no EDID read
in between.

Below is the dmesg representing a video mode set.

ELD writes from the graphics driver

[  424.254958] [drm:intel_write_eld], ELD on [CONNECTOR:12:HDMI-A-2], [ENCODER:11:TMDS-11]
[  424.257670] [drm:ironlake_write_eld], ELD on pipe B
[  424.259833] [drm:ironlake_write_eld], Audio directed to unknown port
[  424.262156] [drm:ironlake_write_eld], ELD size 13

ELD events received by audio driver (eld reads 0)

[  424.263258] HDMI hot plug event: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=0
[  424.265877] HDMI status: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=1
[  424.272415] ALSA hda_eld.c:259 HDMI: Unknown ELD version 0
[  424.274566] HDMI hot plug event: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=1
[  424.277027] HDMI status: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=1
[  424.283157] ALSA hda_eld.c:259 HDMI: Unknown ELD version 0

graphics driver go on with its job

[  424.314331] [drm:intel_wait_for_vblank], vblank wait timed out
[  424.367183] [drm:intel_wait_for_vblank], vblank wait timed out
[  424.368960] [drm:ironlake_update_wm], FIFO watermarks For pipe A - plane 5, cursor: 6
[  424.370700] [drm:ironlake_update_wm], FIFO watermarks For pipe B - plane 42, cursor: 6
[  424.424056] [drm:intel_wait_for_vblank], vblank wait timed out
[  424.476906] [drm:intel_wait_for_vblank], vblank wait timed out
[  424.479169] [drm:ironlake_fdi_link_train], FDI_RX_IIR 0x100
[  424.481084] [drm:ironlake_fdi_link_train], FDI train 1 done.
[  424.483452] [drm:ironlake_fdi_link_train], FDI_RX_IIR 0x600
[  424.485444] [drm:ironlake_fdi_link_train], FDI train 2 done.
[  424.486765] [drm:ironlake_fdi_link_train], FDI train done
[  424.490820] [drm:intel_update_fbc], 
[  424.491841] [drm:drm_crtc_helper_set_config], Setting connector DPMS state to on
[  424.494449] [drm:drm_crtc_helper_set_config],        [CONNECTOR:12:HDMI-A-2] set DPMS on
[  424.505904] [drm:intel_prepare_page_flip], preparing flip with no unpin work?

audio driver repoll the ELD after 300ms (eld data readable now)

[  424.574763] HDMI status: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=1
[  424.580867] HDMI: detected monitor RX-V1800 at connection type HDMI
[  424.582413] HDMI: available speakers: FL/FR LFE FC RL/RR RC RLC/RRC
[  424.584740] HDMI: supports coding type LPCM: channels = 2, rates = 32000 44100 48000 96000 176400 192000 384000, bits = 16 20 24
[  424.587429] HDMI: supports coding type LPCM: channels = 8, rates = 32000 44100 48000 96000 176400 192000 384000, bits = 16 20 24
[  424.590968] HDMI: supports coding type AC-3: channels = 6, rates = 32000 44100 48000, max bitrate = 640000
[  424.594164] HDMI: supports coding type DTS: channels = 7, rates = 32000 44100 48000 96000 176400, max bitrate = 1536000
[  424.597563] HDMI: supports coding type DSD (One Bit Audio): channels = 6, rates = 44100
[  424.600284] HDMI: supports coding type E-AC-3/DD+ (Dolby Digital Plus): channels = 8, rates = 44100 48000
[  424.602420] HDMI: supports coding type MLP (Dolby TrueHD): channels = 8, rates = 48000 176400 384000
[  424.604478] HDMI: supports coding type DTS-HD: channels = 8, rates = 48000 176400 384000

Thanks,
Fengguang