[PATCH v3 0/7] drm/bridge_connector: perform HPD enablement automatically

[Geert Uytterhoeven]

On Tue, Jan 10, 2023 at 8:07 AM Laurentiu Palcu
<laurentiu.palcu at oss.nxp.com> wrote:
> On Mon, Jan 09, 2023 at 10:26:28PM +0200, Dmitry Baryshkov wrote:
> > On 09/01/2023 18:21, Laurentiu Palcu wrote:
> > > It looks like there are some issues with this patchset... :/ I just
> > > fetched the drm-tip and, with these patches included, the "Hot plug
> > > detection already enabled" warning is back for i.MX DCSS.
> >
> > Could you please provide a backtrace?
>
> Sure, see below:
>
> ------------[ cut here ]------------
> Hot plug detection already enabled
> WARNING: CPU: 2 PID: 9 at drivers/gpu/drm/drm_bridge.c:1257 drm_bridge_hpd_enable+0x94/0x9c [drm]
> Modules linked in: videobuf2_memops snd_soc_simple_card snd_soc_simple_card_utils fsl_imx8_ddr_perf videobuf2_common snd_soc_imx_spdif adv7511 etnaviv imx8m_ddrc imx_dcss mc cec nwl_dsi gov
> CPU: 2 PID: 9 Comm: kworker/u8:0 Not tainted 6.2.0-rc2-15208-g25b283acd578 #6
> Hardware name: NXP i.MX8MQ EVK (DT)
> Workqueue: events_unbound deferred_probe_work_func
> pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : drm_bridge_hpd_enable+0x94/0x9c [drm]
> lr : drm_bridge_hpd_enable+0x94/0x9c [drm]
> sp : ffff800009ef3740
> x29: ffff800009ef3740 x28: ffff000009331f00 x27: 0000000000001000
> x26: 0000000000000020 x25: ffff800001148ed8 x24: ffff00000a8fe000
> x23: 00000000fffffffd x22: ffff000005086348 x21: ffff800001133ee0
> x20: ffff00000550d800 x19: ffff000005086288 x18: 0000000000000006
> x17: 0000000000000000 x16: ffff8000096ef008 x15: 97ffff2891004260
> x14: 2a1403e194000000 x13: 97ffff2891004260 x12: 2a1403e194000000
> x11: 7100385f29400801 x10: 0000000000000aa0 x9 : ffff800008112744
> x8 : ffff000000250b00 x7 : 0000000000000003 x6 : 0000000000000011
> x5 : 0000000000000000 x4 : ffff0000bd986a48 x3 : 0000000000000001
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000000250000
> Call trace:
>  drm_bridge_hpd_enable+0x94/0x9c [drm]
>  drm_bridge_connector_enable_hpd+0x2c/0x3c [drm_kms_helper]
>  drm_kms_helper_poll_enable+0x94/0x10c [drm_kms_helper]
>  drm_helper_probe_single_connector_modes+0x1a8/0x510 [drm_kms_helper]
>  drm_client_modeset_probe+0x204/0x1190 [drm]
>  __drm_fb_helper_initial_config_and_unlock+0x5c/0x4a4 [drm_kms_helper]
>  drm_fb_helper_initial_config+0x54/0x6c [drm_kms_helper]
>  drm_fbdev_client_hotplug+0xd0/0x140 [drm_kms_helper]
>  drm_fbdev_generic_setup+0x90/0x154 [drm_kms_helper]
>  dcss_kms_attach+0x1c8/0x254 [imx_dcss]
>  dcss_drv_platform_probe+0x90/0xfc [imx_dcss]
>  platform_probe+0x70/0xcc
>  really_probe+0xc4/0x2e0
>  __driver_probe_device+0x80/0xf0
>  driver_probe_device+0xe0/0x164
>  __device_attach_driver+0xc0/0x13c
>  bus_for_each_drv+0x84/0xe0
>  __device_attach+0xa4/0x1a0
>  device_initial_probe+0x1c/0x30
>  bus_probe_device+0xa4/0xb0
>  deferred_probe_work_func+0x90/0xd0
>  process_one_work+0x200/0x474
>  worker_thread+0x74/0x43c
>  kthread+0xfc/0x110
>  ret_from_fork+0x10/0x20
> ---[ end trace 0000000000000000 ]---

I get a similar trace on R-Car Gen2 (Koelsch with R-Car M2-W) and
Gen3 (Salvator-XS with R-Car H3 ES2.0), and bisected it to commit
92d755d8f13b6791 ("drm/bridge_connector: rely on drm_kms_helper_poll_*
for HPD enablement") in drm-misc/for-linux-next.

As I do not have any displays connected, I do not know what is the
full impact.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds