Unverified Commit 4190e8bb authored by Maxime Ripard's avatar Maxime Ripard
Browse files

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

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: default avatarJavier Martinez Canillas <javierm@redhat.com>
Tested-by: default avatarStefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: default avatarMaxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220929-rpi-pi3-unplugged-fixes-v1-2-cd22e962296c@cerno.tech
parent ae71ab58

drivers/gpu/drm/vc4/vc4_hdmi.c

+20 −0
Original line number Diff line number Diff line
@@ -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)