Files
lbmk/config/coreboot/default/patches/0018-mb-dell-e6400-Use-100-MHz-reference-clock-for-displa.patch
Leah Rowe 1068acd2c0 coreboot/default: new rev ed5a993f
latest coreboot rev as of literally today

this is in preparation for a thinkpad x270 port
using a WIP patch that was contributed

Signed-off-by: Leah Rowe <leah@libreboot.org>
2026-02-19 15:36:22 +00:00

52 lines
1.8 KiB
Diff

From 760ea1634b4b3bcf3dc0aef9b058d383f2c230ab Mon Sep 17 00:00:00 2001
From: Nicholas Chin <nic.c3.14@gmail.com>
Date: Mon, 20 May 2024 10:24:16 -0600
Subject: [PATCH 18/45] mb/dell/e6400: Use 100 MHz reference clock for display
The E6400 uses a 100 MHz reference clock for spread spectrum support on
LVDS, whereas libgfxinit previously assumed a 96 MHz input clock. For
the more common 1280 x 800 display panels, the numerical error was not
large enough to cause noticable issues, but the actual pixel clock
frequency derived from a 100 MHz reference using PLL configs calculated
assuming a 96 MHz reference was not close enough for 1440 x 900 panels,
which require a much higher pixel clock. This resulted in a garbled
display in the pre-OS graphics environment provided by libgfxinit.
Signed-off-by: Nicholas Chin <nic.c3.14@gmail.com>
---
src/mainboard/dell/gm45_latitude/Kconfig | 2 ++
src/northbridge/intel/gm45/Kconfig | 4 ++++
2 files changed, 6 insertions(+)
diff --git a/src/mainboard/dell/gm45_latitude/Kconfig b/src/mainboard/dell/gm45_latitude/Kconfig
index edc79b0d43..5020744990 100644
--- a/src/mainboard/dell/gm45_latitude/Kconfig
+++ b/src/mainboard/dell/gm45_latitude/Kconfig
@@ -22,6 +22,8 @@ config BOARD_DELL_E6400
select BOARD_DELL_GM45_LATITUDE_COMMON
if BOARD_DELL_GM45_LATITUDE_COMMON
+config INTEL_GMA_DPLL_REF_FREQ
+ default 100000000
config MAINBOARD_DIR
default "dell/gm45_latitude"
diff --git a/src/northbridge/intel/gm45/Kconfig b/src/northbridge/intel/gm45/Kconfig
index a776217475..35e89b0c88 100644
--- a/src/northbridge/intel/gm45/Kconfig
+++ b/src/northbridge/intel/gm45/Kconfig
@@ -14,6 +14,10 @@ config NORTHBRIDGE_INTEL_GM45
if NORTHBRIDGE_INTEL_GM45
+config INTEL_GMA_DPLL_REF_FREQ
+ int
+ default 96000000
+
config VBOOT
select VBOOT_STARTS_IN_BOOTBLOCK
--
2.47.3