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From 37b204f22778f51cad7bdf678d7574ff6d7508a6 Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Wed, 25 Mar 2020 18:22:40 +0000
Subject: [PATCH] drm/vc4: Alter the HDMI state machine clock calc to
allow for 1920x1200
Whilst the documentation for BCM2835 states that the HDMI state machine
clock needs to be 108% of the pixel clock, other documentation says
that it only has to be greater than the pixel clock. The firmware
uses 101%, and that allows 1920x1200@60Hz to work within the
constraint of the HSM clock being < 163.68MHz.
Adopt 101%, and increase the maximum pixel clock for vc4 to 162MHz
so that it too supports 1920x1200@60.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
drivers/gpu/drm/vc4/vc4_hdmi.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -581,10 +581,11 @@ static void vc4_hdmi_encoder_enable(stru
}
/*
- * The HSM rate needs to be at 108% of the pixel clock, with a
- * minimum of 108MHz.
+ * The HSM rate needs to be slightly greater than the pixel clock, with
+ * a minimum of 108MHz.
+ * Use 101% as this is what the firmware uses.
*/
- hsm_rate = max_t(unsigned long, 108000000, (pixel_rate / 100) * 108);
+ hsm_rate = max_t(unsigned long, 108000000, (pixel_rate / 100) * 101);
ret = clk_set_rate(vc4_hdmi->hsm_clock, hsm_rate);
if (ret) {
DRM_ERROR("Failed to set HSM clock rate: %d\n", ret);
@@ -1730,7 +1731,7 @@ static int vc4_hdmi_dev_remove(struct pl
}
static const struct vc4_hdmi_variant bcm2835_variant = {
- .max_pixel_clock = 148500000,
+ .max_pixel_clock = 162000000,
.audio_available = true,
.cec_available = true,
.registers = vc4_hdmi_fields,
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