Re: [Intel-gfx] [PATCH v3 2/2] drm/probe_helper: sort out poll_running vs poll_enabled

[Geert Uytterhoeven <geert@linux-m68k.org>]

 	Hi Dmitry,

On Tue, 24 Jan 2023, Dmitry Baryshkov wrote:
> There are two flags attemting to guard connector polling:
> poll_enabled and poll_running. While poll_enabled semantics is clearly
> defined and fully adhered (mark that drm_kms_helper_poll_init() was
> called and not finalized by the _fini() call), the poll_running flag
> doesn't have such clearliness.
>
> This flag is used only in drm_helper_probe_single_connector_modes() to
> guard calling of drm_kms_helper_poll_enable, it doesn't guard the
> drm_kms_helper_poll_fini(), etc. Change it to only be set if the polling
> is actually running. Tie HPD enablement to this flag.
>
> This fixes the following warning reported after merging the HPD series:
>
> 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 ]---
>
> Reported-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
> Fixes: c8268795c9a9 ("drm/probe-helper: enable and disable HPD on connectors")
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> Acked-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
> Tested-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
> Tested-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Thanks for your patch!
This gets rids of the warning splats on e.g. Renesas Koelsch and
Salvator-XS, so
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

 						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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