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

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On 10/01/2023 08:57, Laurentiu Palcu wrote:
Hi,

On Mon, Jan 09, 2023 at 10:26:28PM +0200, Dmitry Baryshkov wrote:
Hi,

On 09/01/2023 18:21, Laurentiu Palcu wrote:
Hi Dmitry,

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:

I wondered, why didn't I see this on msm, my main target nowadays. The msm driver is calling msm_kms_helper_poll_init() after initializing fbdev, so all previous kms_helper_poll_enable() calls return early.

I think I have the fix ready. Let me test it locally before posting.


------------[ 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 ]---

Cheers,
Laurentiu



After a short investigation, it seems that we end up calling
drm_bridge_hpd_enable() from both drm_kms_helper_poll_init() and
drm_fbdev_generic_setup(), hence the warning.

There are drivers using the drm_bridge_connector API that also call
drm_kms_helper_poll_init() followed by drm_fbdev_generic_setup(). So,
they might experience the same behavior, unless I'm missing something...
:/

Also, even if drm_fbdev_generic_setup() is not called in the driver
initialization, the warning will still appear the first time the
GETCONNECTOR ioctl is called, because that'll call
drm_helper_probe_single_connector_modes() helper which will eventually
call drm_bridge_hpd_enable().

Any idea?

Cheers,
Laurentiu

On Wed, Nov 02, 2022 at 09:06:58PM +0300, Dmitry Baryshkov wrote:
  From all the drivers using drm_bridge_connector only iMX/dcss and OMAP
DRM driver do a proper work of calling
drm_bridge_connector_en/disable_hpd() in right places. Rather than
teaching each and every driver how to properly handle
drm_bridge_connector's HPD, make that automatic.

Add two additional drm_connector helper funcs: enable_hpd() and
disable_hpd(). Make drm_kms_helper_poll_* functions call them (as this
is the time where the drm_bridge_connector's functions are called by the
drivers too).

Changes since v2:
   - Fixed a typo in the commit message of the second patch.

Changes since v1:
   - Rebased on top of v6.1-rc1
   - Removed the drm_bridge_connector_enable_hpd() from
     drm_bridge_connector_init()
   - Removed extra underscore prefix from
     drm_bridge_connector_en/disable_hpd() helpers

Dmitry Baryshkov (7):
    drm/poll-helper: merge drm_kms_helper_poll_disable() and _fini()
    drm/probe-helper: enable and disable HPD on connectors
    drm/bridge_connector: rely on drm_kms_helper_poll_* for HPD enablement
    drm/imx/dcss: stop using drm_bridge_connector_en/disable_hpd()
    drm/msm/hdmi: stop using drm_bridge_connector_en/disable_hpd()
    drm/omap: stop using drm_bridge_connector_en/disable_hpd()
    drm/bridge_connector: drop drm_bridge_connector_en/disable_hpd()

   drivers/gpu/drm/drm_bridge_connector.c   | 27 +++-------------
   drivers/gpu/drm/drm_probe_helper.c       | 40 ++++++++++++++++++-----
   drivers/gpu/drm/imx/dcss/dcss-dev.c      |  4 ---
   drivers/gpu/drm/imx/dcss/dcss-kms.c      |  2 --
   drivers/gpu/drm/msm/hdmi/hdmi.c          |  2 --
   drivers/gpu/drm/omapdrm/omap_drv.c       | 41 ------------------------
   include/drm/drm_bridge_connector.h       |  2 --
   include/drm/drm_modeset_helper_vtables.h | 22 +++++++++++++
   8 files changed, 59 insertions(+), 81 deletions(-)

--
2.35.1


--
With best wishes
Dmitry


--
With best wishes
Dmitry




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