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openwrt/target/linux/bcm27xx/patches-5.4/950-0615-vc4_hdmi_phy-Fix-offset-calculation.patch
Álvaro Fernández Rojas f07e572f64 bcm27xx: import latest patches from the RPi foundation
bcm2708: boot tested on RPi B+ v1.2
bcm2709: boot tested on RPi 3B v1.2 and RPi 4B v1.1 4G
bcm2710: boot tested on RPi 3B v1.2
bcm2711: boot tested on RPi 4B v1.1 4G

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
2021-02-18 23:42:32 +01:00

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From 9da2d153eb010d3e92083c322e87de9ae066d93e Mon Sep 17 00:00:00 2001
From: popcornmix <popcornmix@gmail.com>
Date: Thu, 2 Apr 2020 16:46:31 +0100
Subject: [PATCH] vc4_hdmi_phy: Fix offset calculation
The original firmware code worked with float and did
offset = ((vco_freq / fref * 2) * (1 << 22));
offset >>= 2;
In this code it's all integer so doing the integer divide before the shift loses lots of precision
This fixes the issue of 1080p59.94 mode having 59.64 fps
Signed-off-by: popcornmix <popcornmix@gmail.com>
---
drivers/gpu/drm/vc4/vc4_hdmi_phy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/gpu/drm/vc4/vc4_hdmi_phy.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi_phy.c
@@ -192,8 +192,8 @@ static u32 phy_get_rm_offset(unsigned lo
/* RM offset is stored as 9.22 format */
offset = vco_freq * 2;
- do_div(offset, fref);
offset = offset << 22;
+ do_div(offset, fref);
offset >>= 2;
return offset;