From ed9349831a138ac4d2079e59edf40923645f28de Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime@cerno.tech>
Date: Thu, 3 Feb 2022 11:20:03 +0100
Subject: drm/vc4: crtc: Fix runtime_pm reference counting
Git-commit: 6764eb690e77ecded48587d6d4e346ba2e196546
Patch-mainline: v5.17-rc6
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
At boot on the BCM2711, if the HDMI controllers are running, the CRTC
driver will disable itself and its associated HDMI controller to work
around a hardware bug that would leave some pixels stuck in a FIFO.
In order to avoid that issue, we need to run some operations in lockstep
between the CRTC and HDMI controller, and we need to make sure the HDMI
controller will be powered properly.
However, since we haven't enabled it through KMS, the runtime_pm state
is off at this point so we need to make sure the device is powered
through pm_runtime_resume_and_get, and once the operations are complete,
we call pm_runtime_put.
However, the HDMI controller will do that itself in its
post_crtc_powerdown, which means we'll end up calling pm_runtime_put for
a single pm_runtime_get, throwing the reference counting off. Let's
remove the pm_runtime_put call in the CRTC code in order to have the
proper counting.
Fixes: bca10db67bda ("drm/vc4: crtc: Make sure the HDMI controller is powered when disabling")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220203102003.1114673-1-maxime@cerno.tech
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/vc4/vc4_crtc.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index e6cc47470e03..783890e8d43a 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -525,9 +525,11 @@ int vc4_crtc_disable_at_boot(struct drm_crtc *crtc)
if (ret)
return ret;
- ret = pm_runtime_put(&vc4_hdmi->pdev->dev);
- if (ret)
- return ret;
+ /*
+ * post_crtc_powerdown will have called pm_runtime_put, so we
+ * don't need it here otherwise we'll get the reference counting
+ * wrong.
+ */
return 0;
}
--
2.38.1