Merge tag 'drm-misc-fixes-2022-10-13' of git://anongit.freedesktop.org/drm/drm-misc into drm-fixes

Short summary of fixes pull:

 * vc4: HDMI fixes
Signed-off-by: Dave Airlie <airlied@redhat.com>

From: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/Y0gGdlujszCstDeP@linux-uq9g

drivers/gpu/drm/vc4/vc4_drv.c

@@ -490,6 +490,7 @@ module_init(vc4_drm_register);
 module_exit(vc4_drm_unregister);
 
 MODULE_ALIAS("platform:vc4-drm");
+MODULE_SOFTDEP("pre: snd-soc-hdmi-codec");
 MODULE_DESCRIPTION("Broadcom VC4 DRM Driver");
 MODULE_AUTHOR("Eric Anholt <eric@anholt.net>");
 MODULE_LICENSE("GPL v2");

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -3318,12 +3318,37 @@ 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;
 
+	/*
+	 * The HSM clock is in the HDMI power domain, so we need to set
+	 * its frequency while the power domain is active so that it
+	 * keeps its rate.
+	 */
+	ret = clk_set_min_rate(vc4_hdmi->hsm_clock, HSM_MIN_CLOCK_FREQ);
+	if (ret)
+		return ret;
+
 	ret = clk_prepare_enable(vc4_hdmi->hsm_clock);
 	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);
 
@@ -3345,6 +3370,10 @@ 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 void vc4_hdmi_put_ddc_device(void *ptr)