This is a note to let you know that I've just added the patch titled
drm/vc4: hdmi: Check the HSM rate at runtime_resume
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-vc4-hdmi-check-the-hsm-rate-at-runtime_resume.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6359a362b248765e174a6ce4bfc00b19f81f11cd
Author: Maxime Ripard <maxime@xxxxxxxxxx>
Date: Thu Sep 29 11:21:18 2022 +0200
drm/vc4: hdmi: Check the HSM rate at runtime_resume
[ Upstream commit 4190e8bbcbc77a9c36724681801cedc5229e7fc2 ]
If our HSM clock has not been properly initialized, any register access
will silently lock up the system.
Let's check that this can't happen by adding a check for the rate before
any register access, and error out otherwise.
Link: https://lore.kernel.org/dri-devel/20220922145448.w3xfywkn5ecak2et@xxxxxxxxxxxxxx/
Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Tested-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20220929-rpi-pi3-unplugged-fixes-v1-2-cd22e962296c@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 780a19a75c3f..874c6bd787c5 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -2869,6 +2869,7 @@ static int vc4_hdmi_runtime_resume(struct device *dev)
struct vc4_hdmi *vc4_hdmi = dev_get_drvdata(dev);
unsigned long __maybe_unused flags;
u32 __maybe_unused value;
+ unsigned long rate;
int ret;
/*
@@ -2884,6 +2885,21 @@ static int vc4_hdmi_runtime_resume(struct device *dev)
if (ret)
return ret;
+ /*
+ * Whenever the RaspberryPi boots without an HDMI monitor
+ * plugged in, the firmware won't have initialized the HSM clock
+ * rate and it will be reported as 0.
+ *
+ * If we try to access a register of the controller in such a
+ * case, it will lead to a silent CPU stall. Let's make sure we
+ * prevent such a case.
+ */
+ rate = clk_get_rate(vc4_hdmi->hsm_clock);
+ if (!rate) {
+ ret = -EINVAL;
+ goto err_disable_clk;
+ }
+
if (vc4_hdmi->variant->reset)
vc4_hdmi->variant->reset(vc4_hdmi);
@@ -2905,6 +2921,10 @@ static int vc4_hdmi_runtime_resume(struct device *dev)
#endif
return 0;
+
+err_disable_clk:
+ clk_disable_unprepare(vc4_hdmi->hsm_clock);
+ return ret;
}
static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
