From: Maxime Ripard maxime@cerno.tech
[ Upstream commit 3e85b81591609bb794bb00cd619b20965b5b38cd ]
When the firmware doesn't setup the HSM rate (such as when booting without an HDMI cable plugged in), its rate is 0 and thus any register access results in a CPU stall, even though HSM is enabled.
Let's enforce a minimum rate at boot to avoid this issue.
Fixes: 4f6e3d66ac52 ("drm/vc4: Add runtime PM support to the HDMI encoder driver") Signed-off-by: Maxime Ripard maxime@cerno.tech Reviewed-by: Nicolas Saenz Julienne nsaenz@kernel.org Tested-by: Nicolas Saenz Julienne nsaenz@kernel.org Tested-by: Michael Stapelberg michael@stapelberg.ch Link: https://patchwork.freedesktop.org/patch/msgid/20210922125419.4125779-4-maxim... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/vc4/vc4_hdmi.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c index ee293f061f0a8..5d5c4e9a86218 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c @@ -79,6 +79,7 @@ # define VC4_HD_M_SW_RST BIT(2) # define VC4_HD_M_ENABLE BIT(0)
+#define HSM_MIN_CLOCK_FREQ 120000000 #define CEC_CLOCK_FREQ 40000 #define VC4_HSM_MID_CLOCK 149985000
@@ -1806,6 +1807,19 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data) vc4_hdmi->disable_wifi_frequencies = of_property_read_bool(dev->of_node, "wifi-2.4ghz-coexistence");
+ /* + * If we boot without any cable connected to the HDMI connector, + * the firmware will skip the HSM initialization and leave it + * with a rate of 0, resulting in a bus lockup when we're + * accessing the registers even if it's enabled. + * + * Let's put a sensible default at runtime_resume so that we + * don't end up in this situation. + */ + ret = clk_set_min_rate(vc4_hdmi->hsm_clock, HSM_MIN_CLOCK_FREQ); + if (ret) + goto err_put_ddc; + if (vc4_hdmi->variant->reset) vc4_hdmi->variant->reset(vc4_hdmi);