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

[sfrench/cifs-2.6.git] / drivers / gpu / drm / vc4 / vc4_hdmi.c

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 64f9feabf43ef92c63ad7f8c4e164650e452d7e4..596e311d6e58eaf7c2c914b531643f7d34979052 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/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)