target/linux/bcm27xx/patches-6.1/950-0950-drm-vc4-hdmi-Avoid-hang-with-debug-registers-when-su.patch

   1 From e5e7679d634b10e88df340c85cd8368c9f9989eb Mon Sep 17 00:00:00 2001
   2 From: Dom Cobley <popcornmix@gmail.com>
   3 Date: Tue, 5 Sep 2023 19:38:24 +0100
   4 Subject: [PATCH] drm/vc4: hdmi: Avoid hang with debug registers when suspended
   5
   6 Trying to read /sys/kernel/debug/dri/1/hdmi1_regs
   7 when the hdmi is disconnected results in a fatal system hang.
   8
   9 This is due to the pm suspend code disabling the dvp clock.
  10 That is just a gate of the 108MHz clock in DVP_HT_RPI_MISC_CONFIG,
  11 which results in accesses hanging AXI bus.
  12
  13 Protect against this.
  14
  15 Signed-off-by: Dom Cobley <popcornmix@gmail.com>
  16 ---
  17  drivers/gpu/drm/vc4/vc4_hdmi.c | 4 ++++
  18  1 file changed, 4 insertions(+)
  19
  20 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
  21 +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
  22 @@ -193,6 +193,8 @@ static int vc4_hdmi_debugfs_regs(struct
  23         if (!drm_dev_enter(drm, &idx))
  24                 return -ENODEV;
  25
  26 +       WARN_ON(pm_runtime_resume_and_get(&vc4_hdmi->pdev->dev));
  27 +
  28         drm_print_regset32(&p, &vc4_hdmi->hdmi_regset);
  29         drm_print_regset32(&p, &vc4_hdmi->hd_regset);
  30         drm_print_regset32(&p, &vc4_hdmi->cec_regset);
  31 @@ -202,6 +204,8 @@ static int vc4_hdmi_debugfs_regs(struct
  32         drm_print_regset32(&p, &vc4_hdmi->ram_regset);
  33         drm_print_regset32(&p, &vc4_hdmi->rm_regset);
  34
  35 +       pm_runtime_put(&vc4_hdmi->pdev->dev);
  36 +
  37         drm_dev_exit(idx);
  38
  39         return 0;