[PATCH v7 00/10] drm: add DRM HDMI Codec framework

[Dave Stevenson]

On Wed, 18 Dec 2024 at 14:52, Dave Stevenson
<dave.stevenson at raspberrypi.com> wrote:
>
> Hi Maxime & Dmitry
>
> On Wed, 18 Dec 2024 at 07:59, Maxime Ripard <mripard at kernel.org> wrote:
> >
> > On Wed, Dec 18, 2024 at 07:24:23AM +0200, Dmitry Baryshkov wrote:
> > > On Tue, 17 Dec 2024 at 19:21, Maxime Ripard <mripard at kernel.org> wrote:
> > > > On Tue, Dec 17, 2024 at 02:40:22AM +0200, Dmitry Baryshkov wrote:
> > > > > While porting lt9611 DSI-to-HDMI bridge driver to use HDMI Connector
> > > > > framework, I stumbled upon an issue while handling the Audio InfoFrames.
> > > > > The HDMI codec callbacks weren't receiving the drm_atomic_state, so
> > > > > there was no simple way to get the drm_connector that stayed at the end
> > > > > of the bridge chain. At the same point the drm_hdmi_connector functions
> > > > > expected to get drm_connector instance.
> > > > >
> > > > > While looking for a way to solve the issue, I stumbled upon several
> > > > > deficiencies in existing hdmi_codec_ops implementations. Only few of the
> > > > > implementations were able to handle codec's 'plugged' callback. One
> > > > > third of the drivers didn't implement the get_eld() callback.
> > > > >
> > > > > Most of the issues can be solved if drm_connector handles
> > > > > hdmi-audio-codec on its own, delegating functionality to the actual
> > > > > implementation, be it a driver that implements drm_connector or
> > > > > drm_bridge.
> > > > >
> > > > > Implement such high-level framework, adding proper support for Audio
> > > > > InfoFrame generation to the LT9611 driver.
> > > > >
> > > > > Several design decisions to be kept in mind:
> > > > >
> > > > > - drm_connector_hdmi_codec is kept as simple as possible. It implements
> > > > >   generic functionality (ELD, hotplug, registration).
> > > > >
> > > > > - drm_hdmi_connector sets up HDMI codec device if the connector
> > > > >   is setup correspondingly (either I2S or S/PDIF is marked as
> > > > >   supported).
> > > > >
> > > > > - drm_bridge_connector provides a way to link HDMI audio codec
> > > > >   funcionality in the drm_bridge with the drm_connector_hdmi_codec
> > > > >   framework.
> > > > >
> > > > > - It might be worth reverting the no_i2s_capture / no_spdif_capture
> > > > >   bits. Only TDA889x driver sets them, while it's safe to assume that
> > > > >   most of HDMI / DP devices do not support ARC / capture. I think the
> > > > >   drivers should opt-in capture support rather than having to opt-out of
> > > > >   it.
> > > >
> > > > Sorry if this isn't clear to me and I'm quite late to the party, but did
> > > > you test this on vc4 with both a pi3 and pi4, or was it just compile
> > > > tested?
> > >
> > > LT9611 is actually tested, VC4 is only compile-tested. Should I put an RFT tag?
> >
> > Yeah, we definitely need to test it on the pi3 (polling-based) and the
> > pi4 (irq-based) at least.
> >
> > Dave, Maira, could you give it a try?
>
> I'm on it.

Basic checks look OK.
Pi3 and Pi4 tested, including 4k60 on Pi4 (enables scrambling). Audio
works, and all the EDID parsing seems to be correct.

Ideally I would like to do a couple more tests though as I had a
couple of spontaneous reboots on Pi4 whilst hotplugging.
Most likely it was just grounding issues, as I can't think of an
obvious way for the kernel to be triggering an automatic reboot. They
seemed to go away when I had enabled drm.debug=0x14, but more likely
I'd connected the serial port and therefore provided another ground.
Please don't hold the patches waiting on me though - I don't know when
I'll have time to do them.


Also unrelated to this patch set, I have noted I'm getting
[   60.780897] WARNING: CPU: 3 PID: 501 at
drivers/gpu/drm/vc4/vc4_hvs.c:743 __vc4_hvs_stop_channel+0x148/0x164
[vc4]
...
[   60.781192]  __vc4_hvs_stop_channel+0x148/0x164 [vc4] (P)
[   60.781212]  __vc4_hvs_stop_channel+0x40/0x164 [vc4] (L)
[   60.781230]  vc4_hvs_stop_channel+0x30/0x3c [vc4]
[   60.781248]  vc4_crtc_disable+0x140/0x1e8 [vc4]
[   60.781266]  vc4_crtc_atomic_disable+0x98/0xb8 [vc4]
[   60.781284]  disable_outputs+0x22c/0x33c [drm_kms_helper]
[   60.781326]  drm_atomic_helper_commit_modeset_disables+0x1c/0x4c
[drm_kms_helper]
[   60.781347]  vc4_atomic_commit_tail+0x10c/0x8e4 [vc4]
[   60.781364]  commit_tail+0xa0/0x188 [drm_kms_helper]
[   60.781385]  drm_atomic_helper_commit+0x16c/0x180 [drm_kms_helper]
[   60.781406]  drm_atomic_commit+0x88/0xc4 [drm]
[   60.781500]  drm_client_modeset_commit_atomic+0x204/0x264 [drm]
[   60.781553]  drm_client_modeset_commit_locked+0x5c/0x198 [drm]
[   60.781603]  drm_client_modeset_commit+0x30/0x58 [drm]
[   60.781652]  __drm_fb_helper_restore_fbdev_mode_unlocked+0xb4/0xe8
[drm_kms_helper]
[   60.781674]  drm_fb_helper_hotplug_event+0x108/0x12c [drm_kms_helper]
[   60.781695]  drm_fbdev_client_hotplug+0x28/0xd4 [drm_client_lib]
[   60.781700]  drm_client_dev_hotplug+0xc8/0x12c [drm]
[   60.781750]  drm_connector_helper_hpd_irq_event+0x70/0xb0 [drm_kms_helper]
[   60.781771]  vc4_hdmi_hpd_irq_thread+0x2c/0x3c [vc4]
[   60.781790]  irq_thread_fn+0x2c/0xa8
[   60.781799]  irq_thread+0x16c/0x2f4
[   60.781805]  kthread+0x118/0x11c
[   60.781813]  ret_from_fork+0x10/0x20
On first plugging or unplugging a second monitor. I suspect that is
spurious though and I'll look into it, but probably not this side of
the Christmas break.

  Dave