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

Dmitry Baryshkov
2024-12-20T00:45:24Z

On Thu, Dec 19, 2024 at 04:16:37PM +0000, Dave Stevenson wrote:
> On Wed, 18 Dec 2024 at 14:52, Dave Stevenson
> <dave.stevenson@raspberrypi.com> wrote:
> >
> > Hi Maxime & Dmitry
> >
> > On Wed, 18 Dec 2024 at 07:59, Maxime Ripard <mripard@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@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.

Tested-by?

>
>
> 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

--
With best wishes
Dmitry