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

Tue Jan 10 06:57:12 UTC 2023

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:

------------[ 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
> 