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drm/vc4: hdmi: Check the HSM rate at runtime_resume

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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@pengutronix.de/
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220929-rpi-pi3-unplugged-fixes-v1-2-cd22e962296c@cerno.tech
This commit is contained in:
Maxime Ripard
2022-09-29 11:21:18 +02:00
parent ae71ab585c
commit 4190e8bbcb
1 changed files with 20 additions and 0 deletions
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20
drivers/gpu/drm/vc4/vc4_hdmi.c
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@@ -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)