drm/vc4: hdmi: Adjust HSM clock rate depending on pixel rate

The HSM clock needs to be setup at around 101% of the pixel rate. This
was done previously by setting the clock rate to 163.7MHz at probe time and
only check in mode_valid whether the mode pixel clock was under the pixel
clock +1% or not.

However, with 4k we need to change that frequency to a higher frequency
than 163.7MHz, and yet want to have the lowest clock as possible to have a
decent power saving.

Let's change that logic a bit by setting the clock rate of the HSM clock
to the pixel rate at encoder_enable time. This would work for the
BCM2711 that support 4k resolutions and has a clock that can provide it,
but we still have to take care of a 4k panel plugged on a BCM283x SoCs
that wouldn't be able to use those modes, so let's define the limit in
the variant.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/7e692ddc231d33dd671e70ea04dd1dcf56c1ecb3.1599120059.git-series.maxime@cerno.tech

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
index 3f07aebe89f1..342f6e0227a2 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.h
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
@@ -36,6 +36,9 @@ struct vc4_hdmi_variant {
 	/* Set to true when the CEC support is available */
 	bool cec_available;
 
+	/* Maximum pixel clock supported by the controller (in Hz) */
+	unsigned long long max_pixel_clock;
+
 	/* List of the registers available on that variant */
 	const struct vc4_hdmi_register *registers;