[PATCH 2/2] drm/vc4: hdmi: Check the HSM rate at runtime_resume
Maxime Ripard
maxime at cerno.tech
Thu Sep 29 09:21:18 UTC 2022
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/
Signed-off-by: Maxime Ripard <maxime at cerno.tech>
---
drivers/gpu/drm/vc4/vc4_hdmi.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 2e28fe16ed5e..eb3aaaca2b80 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -2889,6 +2889,7 @@ 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;
/*
@@ -2904,6 +2905,21 @@ 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);
@@ -2925,6 +2941,10 @@ 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)
--
b4 0.10.1
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