[PATCH v2 1/2] drm/i915/hpd: postpone HPD cancel work after last user suspension

[Andrzej Hajda]

i915->hotplug.dig_port_work can be queued from intel_hpd_irq_handler
called by IRQ handler or by intel_hpd_trigger_irq called from dp_mst.
Since dp_mst is suspended after irq handler uninstall, a cleaner approach
is to cancel hpd work after intel_dp_mst_suspend, otherwise we risk
use-after-free.

It should fix following WARNINGS:
[283.405824] cpu_latency_qos_update_request called for unknown object
[283.405866] WARNING: CPU: 2 PID: 240 at kernel/power/qos.c:296 cpu_latency_qos_update_request+0x2d/0x100
[283.405912] CPU: 2 PID: 240 Comm: kworker/u64:9 Not tainted 5.18.0-rc6-Patchwork_103738v3-g1672d1c43e43+ #1
[283.405915] Hardware name: Intel Corporation Raptor Lake Client Platform/RPL-S ADP-S DDR5 UDIMM CRB, BIOS RPLSFWI1.R00.2397.A01.2109300731 09/30/2021
[283.405916] Workqueue: i915-dp i915_digport_work_func [i915]
[283.406020] RIP: 0010:cpu_latency_qos_update_request+0x2d/0x100
...
[283.406040] Call Trace:
[283.406041]  <TASK>
[283.406044]  intel_dp_aux_xfer+0x60e/0x8e0 [i915]
[283.406131]  ? finish_swait+0x80/0x80
[283.406139]  intel_dp_aux_transfer+0xc5/0x2b0 [i915]
[283.406218]  drm_dp_dpcd_access+0x79/0x130 [drm_display_helper]
[283.406227]  drm_dp_dpcd_read+0xe2/0xf0 [drm_display_helper]
[283.406233]  intel_dp_hpd_pulse+0x134/0x570 [i915]
[283.406308]  ? __down_killable+0x70/0x140
[283.406313]  i915_digport_work_func+0xba/0x150 [i915]

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4586
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5558
Signed-off-by: Andrzej Hajda <andrzej.hajda at intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 3 +++
 drivers/gpu/drm/i915/i915_irq.c              | 1 -
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 903226e2a6260d..ec8e59b3adaea7 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -9007,6 +9007,9 @@ void intel_modeset_driver_remove_noirq(struct drm_i915_private *i915)
 	 */
 	intel_dp_mst_suspend(i915);
 
+	/* MST is the last user of HPD work */
+	intel_hpd_cancel_work(i915);
+
 	/* poll work can call into fbdev, hence clean that up afterwards */
 	intel_fbdev_fini(i915);
 
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 73cebc6aa65072..db14787aef95dd 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -4597,7 +4597,6 @@ void intel_irq_uninstall(struct drm_i915_private *dev_priv)
 
 	free_irq(irq, dev_priv);
 
-	intel_hpd_cancel_work(dev_priv);
 	dev_priv->runtime_pm.irqs_enabled = false;
 }
 
-- 
2.25.1