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charset="us-ascii" Content-Disposition: inline List-Id: X-Webhook-Received: from li982-79.members.linode.com [45.33.32.79] by aws-us-west-2-korg-lkml-1.web.codeaurora.org with HTTPS for ; Wed, 06 Aug 2025 01:16:18 -0000 X-Groupsio-URL: https://lists.cip-project.org/g/cip-dev/message/19674 On Tue, Aug 05, 2025 at 01:46:51PM +0300, Dmitry Baryshkov wrote: > On Mon, Aug 04, 2025 at 11:13:59PM +0300, Nicusor Huhulea wrote: > > A regression in output polling was introduced by commit 4ad8d57d902fbc7c82507cfc1b031f3a07c3de6e > > ("drm: Check output polling initialized before disabling") in the 6.1.y stable tree. > > As a result, when the i915 driver detects an HPD IRQ storm and attempts to switch > > from IRQ-based hotplug detection to polling, output polling fails to resume. > > > > The root cause is the use of dev->mode_config.poll_running. Once poll_running is set > > (during the first connector detection) the calls to drm_kms_helper_poll_enable(), such as > > intel_hpd_irq_storm_switch_to_polling() fails to schedule output_poll_work as expected. > > Therefore, after an IRQ storm disables HPD IRQs, polling does not start, breaking hotplug detection. > > Why doesn't disable path use drm_kms_helper_poll_disable() ? In general i915 doesn't disable polling as a whole after an IRQ storm and a 2 minute delay (or runtime resuming), since on some other connectors the polling may be still required. Also, in the 6.1.y stable tree drm_kms_helper_poll_disable() is: if (drm_WARN_ON(dev, !dev->mode_config.poll_enabled)) return; cancel_delayed_work_sync(&dev->mode_config.output_poll_work); so calling that wouldn't really fix the problem, which is clearly just an incorrect backport of the upstream commit 5abffb66d12bcac8 ("drm: Check output polling initialized before disabling") to the v6.1.y stable tree by commit 4ad8d57d902f ("drm: Check output polling initialized before disabling") in v6.1.y. The upstream commit did not add the check for dev->mode_config.poll_running in drm_kms_helper_poll_enable(), the condition was only part of the diff context in the commit. Hence adding the condition in the 4ad8d57d902f backport commit was incorrect. > > The fix is to remove the dev->mode_config.poll_running in the check condition, ensuring polling > > is always scheduled as requested. > > > > Notes: > > Initial analysis, assumptions, device testing details, the correct fix and detailed rationale > > were discussed here https://lore.kernel.org/stable/aI32HUzrT95nS_H9@ideak-desk/ > > > > -- > With best wishes > Dmitry