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drm/vc4: hdmi: Set a default HSM rate

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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: 4f6e3d66ac ("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-maxime@cerno.tech
This commit is contained in:
Maxime Ripard 2021-09-22 14:54:17 +02:00
parent 8ca011ef4a
commit 3e85b81591
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GPG Key ID: E3EF0D6F671851C5
1 changed files with 14 additions and 0 deletions
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14
drivers/gpu/drm/vc4/vc4_hdmi.c
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@ -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)
@ -2170,6 +2171,19 @@ 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);