On Wed, Nov 16, 2011 at 11:51:28PM +0800, Stephen Warren wrote:
Wu Fengguang wrote at Tuesday, November 15, 2011 7:48 PM:
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 = 1OK, that sounds fine.
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
That line makes sense.
[ 424.265877] HDMI status: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=1
I don't /think/ it's related to this issue, but I wonder why ELDV==1 in that message; it seems that the unsolicited response contains the correct data, but AC_VERB_GET_PIN_SENSE contains ELDV==1 all the time. That's odd.
It depends on timing. When audio driver receives the unsolicited event, graphics driver has finished with "eld_valid = 1", hence AC_VERB_GET_PIN_SENSE returns ELDV=1.
It's not happening /all the time/ though. For example here is another dmesg showing a different timing on the same test box.
[ 467.561516] [drm:intel_dp_mode_set], Enabling DP audio on pipe B [ 467.567503] [drm:intel_write_eld], ELD on [CONNECTOR:26:DP-3], [ENCODER:27:TMDS-27] [ 467.574207] [drm:ironlake_write_eld], ELD on pipe B [ 467.579346] [drm:ironlake_write_eld], Audio directed to unknown port [ 467.584724] [drm:ironlake_write_eld], ELD: DisplayPort detected [ 467.586540] HDMI hot plug event: Codec=3 Pin=7 Presence_Detect=1 ELD_Valid=0 [ 467.599608] [drm:ironlake_write_eld], [ 467.599922] HDMI status: Codec=3 Pin=7 Presence_Detect=1 ELD_Valid=0 [ 467.605834] ELD size 9 [ 467.610434] [drm:sandybridge_update_wm], FIFO watermarks For pipe A - plane 7, cursor: 6 [ 467.612365] HDMI hot plug event: Codec=3 Pin=7 Presence_Detect=1 ELD_Valid=1 [ 467.620654] [drm:sandybridge_update_wm], [ 467.620765] HDMI status: Codec=3 Pin=7 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
...
OK, well I guess this make it work, and I don't think the patch will cause any issues on HW without this issue, so the patch is fine. I'd still love to understand why this is happening though.
I'd like to know the root cause, too... However enabling drm debugging does not show any co-related event that turns the ELD into readable state, and I cannot find clues in the spec, too...
Thanks, Fengguang