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

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jan 24, 2023 at 12:45:48PM +0200, 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 apparently broke something in i915. I suspect polling
is no longer happening correctly while the device is runtime
suspended.

https://gitlab.freedesktop.org/drm/intel/-/issues/8451

> 
> 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>
> ---
>  drivers/gpu/drm/drm_probe_helper.c | 42 +++++++++++++++---------------
>  1 file changed, 21 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index ab787d71fa66..8127be134c39 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -282,7 +282,8 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
>  	bool poll = false;
>  	unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
>  
> -	if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
> +	if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll ||
> +	    dev->mode_config.poll_running)
>  		return;
>  
>  	poll = drm_kms_helper_enable_hpd(dev);
> @@ -304,6 +305,8 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
>  
>  	if (poll)
>  		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
> +
> +	dev->mode_config.poll_running = true;
>  }
>  EXPORT_SYMBOL(drm_kms_helper_poll_enable);
>  
> @@ -592,10 +595,7 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
>  	}
>  
>  	/* Re-enable polling in case the global poll config changed. */
> -	if (drm_kms_helper_poll != dev->mode_config.poll_running)
> -		drm_kms_helper_poll_enable(dev);
> -
> -	dev->mode_config.poll_running = drm_kms_helper_poll;
> +	drm_kms_helper_poll_enable(dev);
>  
>  	if (connector->status == connector_status_disconnected) {
>  		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
> @@ -735,8 +735,11 @@ static void output_poll_execute(struct work_struct *work)
>  	changed = dev->mode_config.delayed_event;
>  	dev->mode_config.delayed_event = false;
>  
> -	if (!drm_kms_helper_poll)
> +	if (!drm_kms_helper_poll && dev->mode_config.poll_running) {
> +		drm_kms_helper_disable_hpd(dev);
> +		dev->mode_config.poll_running = false;
>  		goto out;
> +	}
>  
>  	if (!mutex_trylock(&dev->mode_config.mutex)) {
>  		repoll = true;
> @@ -833,19 +836,6 @@ bool drm_kms_helper_is_poll_worker(void)
>  }
>  EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);
>  
> -static void drm_kms_helper_poll_disable_fini(struct drm_device *dev, bool fini)
> -{
> -	if (!dev->mode_config.poll_enabled)
> -		return;
> -
> -	if (fini)
> -		dev->mode_config.poll_enabled = false;
> -
> -	drm_kms_helper_disable_hpd(dev);
> -
> -	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
> -}
> -
>  /**
>   * drm_kms_helper_poll_disable - disable output polling
>   * @dev: drm_device
> @@ -862,7 +852,12 @@ static void drm_kms_helper_poll_disable_fini(struct drm_device *dev, bool fini)
>   */
>  void drm_kms_helper_poll_disable(struct drm_device *dev)
>  {
> -	drm_kms_helper_poll_disable_fini(dev, false);
> +	if (dev->mode_config.poll_running)
> +		drm_kms_helper_disable_hpd(dev);
> +
> +	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
> +
> +	dev->mode_config.poll_running = false;
>  }
>  EXPORT_SYMBOL(drm_kms_helper_poll_disable);
>  
> @@ -900,7 +895,12 @@ EXPORT_SYMBOL(drm_kms_helper_poll_init);
>   */
>  void drm_kms_helper_poll_fini(struct drm_device *dev)
>  {
> -	drm_kms_helper_poll_disable_fini(dev, true);
> +	if (!dev->mode_config.poll_enabled)
> +		return;
> +
> +	drm_kms_helper_poll_disable(dev);
> +
> +	dev->mode_config.poll_enabled = false;
>  }
>  EXPORT_SYMBOL(drm_kms_helper_poll_fini);
>  
> -- 
> 2.39.0

-- 
Ville Syrjälä
Intel