From cc018c2626745d2e52273f941f9db222101aa11a Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Wed, 9 Aug 2023 13:43:05 +0300 Subject: [PATCH] drm/i915: Avoid endless HPD poll detect loop via runtime suspend/resume MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The issue fixed in commit a8ddac7c9f06 ("drm/i915: Avoid HPD poll detect triggering a new detect cycle") on VLV, CHV is still present on platforms where the display hotplug detection functionality is available whenever the device is in D0 state (hence these platforms switch to HPD polling only when the device is runtime suspended). The above commit avoids an endless i915_hpd_poll_init_work() -> connector detect loop by making sure that by the end of i915_hpd_poll_init_work() all display power references acquired by the connector detect functions which can trigger a new cycle (display core power domain) are dropped. However on platforms where HPD polling is enabled/disabled only from the runtime suspend/resume handlers, this is not ensured: for instance eDP VDD, TypeC port PHYs and the runtime autosuspend delay may still keep the device runtime resumed (via a power reference acquired during connector detection and hence result in an endless loop like the above). Solve the problem described in the above commit on all platforms, by making sure that a i915_hpd_poll_init_work() -> connector detect sequence can't take any power reference in the first place which would trigger a new cycle, instead of relying on these power references to be dropped by the end of the sequence. With the default runtime autosuspend delay (10 sec) this issue didn't happen in practice, since the device remained runtime resumed for the whole duration of the above sequence. CI/IGT tests however set the autosuspend delay to 0, which makes the problem visible, see References: below. Tested on GLK, CHV. v2: Don't warn about a requeued work, to account for disabling polling directly during driver loading, reset and system resume. References: https://gitlab.freedesktop.org/drm/intel/-/issues/7940#note_1997403 Signed-off-by: Imre Deak Reviewed-by: Jouni Högander Link: https://patchwork.freedesktop.org/patch/msgid/20230809104307.1218058-1-imre.deak@intel.com --- drivers/gpu/drm/i915/display/intel_crt.c | 6 ------ drivers/gpu/drm/i915/display/intel_dp.c | 6 ------ drivers/gpu/drm/i915/display/intel_hdmi.c | 6 ------ drivers/gpu/drm/i915/display/intel_hotplug.c | 22 +++++++++++++++++++- 4 files changed, 21 insertions(+), 19 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_crt.c b/drivers/gpu/drm/i915/display/intel_crt.c index 809074758687..f66340b4caf0 100644 --- a/drivers/gpu/drm/i915/display/intel_crt.c +++ b/drivers/gpu/drm/i915/display/intel_crt.c @@ -907,12 +907,6 @@ load_detect: out: intel_display_power_put(dev_priv, intel_encoder->power_domain, wakeref); - /* - * Make sure the refs for power wells enabled during detect are - * dropped to avoid a new detect cycle triggered by HPD polling. - */ - intel_display_power_flush_work(dev_priv); - return status; } diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 12bd2f322e62..964bf0551bdc 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -4957,12 +4957,6 @@ out: if (status != connector_status_connected && !intel_dp->is_mst) intel_dp_unset_edid(intel_dp); - /* - * Make sure the refs for power wells enabled during detect are - * dropped to avoid a new detect cycle triggered by HPD polling. - */ - intel_display_power_flush_work(dev_priv); - if (!intel_dp_is_edp(intel_dp)) drm_dp_set_subconnector_property(connector, status, diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c index 94a7e1537f42..9442bf43550e 100644 --- a/drivers/gpu/drm/i915/display/intel_hdmi.c +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c @@ -2522,12 +2522,6 @@ out: if (status != connector_status_connected) cec_notifier_phys_addr_invalidate(intel_hdmi->cec_notifier); - /* - * Make sure the refs for power wells enabled during detect are - * dropped to avoid a new detect cycle triggered by HPD polling. - */ - intel_display_power_flush_work(dev_priv); - return status; } diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c index 0ff5ed46ae1e..dd7eb9fc7861 100644 --- a/drivers/gpu/drm/i915/display/intel_hotplug.c +++ b/drivers/gpu/drm/i915/display/intel_hotplug.c @@ -25,6 +25,7 @@ #include "i915_drv.h" #include "i915_irq.h" +#include "intel_display_power.h" #include "intel_display_types.h" #include "intel_hotplug.h" #include "intel_hotplug_irq.h" @@ -638,11 +639,25 @@ static void i915_hpd_poll_init_work(struct work_struct *work) display.hotplug.poll_init_work); struct drm_connector_list_iter conn_iter; struct intel_connector *connector; + intel_wakeref_t wakeref; bool enabled; mutex_lock(&dev_priv->drm.mode_config.mutex); enabled = READ_ONCE(dev_priv->display.hotplug.poll_enabled); + /* + * Prevent taking a power reference from this sequence of + * i915_hpd_poll_init_work() -> drm_helper_hpd_irq_event() -> + * connector detect which would requeue i915_hpd_poll_init_work() + * and so risk an endless loop of this same sequence. + */ + if (!enabled) { + wakeref = intel_display_power_get(dev_priv, + POWER_DOMAIN_DISPLAY_CORE); + drm_WARN_ON(&dev_priv->drm, + READ_ONCE(dev_priv->display.hotplug.poll_enabled)); + cancel_work(&dev_priv->display.hotplug.poll_init_work); + } drm_connector_list_iter_begin(&dev_priv->drm, &conn_iter); for_each_intel_connector_iter(connector, &conn_iter) { @@ -669,8 +684,13 @@ static void i915_hpd_poll_init_work(struct work_struct *work) * We might have missed any hotplugs that happened while we were * in the middle of disabling polling */ - if (!enabled) + if (!enabled) { drm_helper_hpd_irq_event(&dev_priv->drm); + + intel_display_power_put(dev_priv, + POWER_DOMAIN_DISPLAY_CORE, + wakeref); + } } /** -- 2.25.1