From 7f213fb817a90f0cb5aba2ff7746816f4238534c Mon Sep 17 00:00:00 2001 From: Dom Cobley 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 --- drivers/gpu/drm/vc4/vc4_hdmi.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c index a546853..18c79be 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c @@ -185,6 +185,8 @@ static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused) 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); @@ -194,6 +196,8 @@ static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused) 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; -- 2.7.4