| Message ID | 20210922125419.4125779-4-maxime@cerno.tech (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/vc4: hdmi: Remove CPU hangs, take 2 | expand |
On Wed, 2021-09-22 at 14:54 +0200, Maxime Ripard wrote: > 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> Regards, Nicolas
On Wed, 22 Sep 2021 14:54:17 +0200, Maxime Ripard wrote: > 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. > > > [...] Applied to drm/drm-misc (drm-misc-fixes). Thanks! Maxime
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c index b4b4653fe301..74222b12f8c8 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c @@ -94,6 +94,7 @@ # 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 HDMI_14_MAX_TMDS_CLK (340 * 1000 * 1000) @@ -2169,6 +2170,19 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data) vc4_hdmi->disable_4kp60 = true; } + /* + * 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);
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> --- drivers/gpu/drm/vc4/vc4_hdmi.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)