Unverified Commit 3e85b815 authored by Maxime Ripard's avatar Maxime Ripard
Browse files

drm/vc4: hdmi: Set a default HSM rate 



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: 4f6e3d66 ("drm/vc4: Add runtime PM support to the HDMI encoder driver")
Signed-off-by: default avatarMaxime Ripard <maxime@cerno.tech>
Reviewed-by: default avatarNicolas Saenz Julienne <nsaenz@kernel.org>
Tested-by: default avatarNicolas Saenz Julienne <nsaenz@kernel.org>
Tested-by: default avatarMichael Stapelberg <michael@stapelberg.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210922125419.4125779-4-maxime@cerno.tech
parent 8ca011ef

drivers/gpu/drm/vc4/vc4_hdmi.c

+14 −0
Original line number Diff line number Diff line
@@ -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);