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From e5e7679d634b10e88df340c85cd8368c9f9989eb Mon Sep 17 00:00:00 2001
From: Dom Cobley <popcornmix@gmail.com>
Date: Tue, 5 Sep 2023 19:38:24 +0100
Subject: [PATCH] drm/vc4: hdmi: Avoid hang with debug registers when suspended
Trying to read /sys/kernel/debug/dri/1/hdmi1_regs
when the hdmi is disconnected results in a fatal system hang.
This is due to the pm suspend code disabling the dvp clock.
That is just a gate of the 108MHz clock in DVP_HT_RPI_MISC_CONFIG,
which results in accesses hanging AXI bus.
Protect against this.
Signed-off-by: Dom Cobley <popcornmix@gmail.com>
---
drivers/gpu/drm/vc4/vc4_hdmi.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -193,6 +193,8 @@ static int vc4_hdmi_debugfs_regs(struct
if (!drm_dev_enter(drm, &idx))
return -ENODEV;
+ WARN_ON(pm_runtime_resume_and_get(&vc4_hdmi->pdev->dev));
+
drm_print_regset32(&p, &vc4_hdmi->hdmi_regset);
drm_print_regset32(&p, &vc4_hdmi->hd_regset);
drm_print_regset32(&p, &vc4_hdmi->cec_regset);
@@ -202,6 +204,8 @@ static int vc4_hdmi_debugfs_regs(struct
drm_print_regset32(&p, &vc4_hdmi->ram_regset);
drm_print_regset32(&p, &vc4_hdmi->rm_regset);
+ pm_runtime_put(&vc4_hdmi->pdev->dev);
+
drm_dev_exit(idx);
return 0;
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