Merge pull request 'Fix E6400 display issue with 1440 x 900 panel' (#211) from nic3-14159/lbmk:fix-e6400-igpu-ref-clock into master

Reviewed-on: https://codeberg.org/libreboot/lbmk/pulls/211

1 files changed, 36 insertions, 0 deletions

diff --git a/config/coreboot/dell/patches/0010-mb-dell-e6400-Use-100-MHz-reference-clock-for-displa.patch b/config/coreboot/dell/patches/0010-mb-dell-e6400-Use-100-MHz-reference-clock-for-displa.patch
new file mode 100644
index 00000000..7f85d0ed
--- /dev/null
+++ b/config/coreboot/dell/patches/0010-mb-dell-e6400-Use-100-MHz-reference-clock-for-displa.patch
@@ -0,0 +1,36 @@
+From c35d431a0f1b326b18cd5bbb7d1d49e67d3309bd 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] 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/e6400/Kconfig | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/src/mainboard/dell/e6400/Kconfig b/src/mainboard/dell/e6400/Kconfig
+index 034de4be2b..4cb16af697 100644
+--- a/src/mainboard/dell/e6400/Kconfig
++++ b/src/mainboard/dell/e6400/Kconfig
+@@ -17,6 +17,9 @@ config BOARD_SPECIFIC_OPTIONS
+ 	select INTEL_GMA_HAVE_VBT
+ 	select EC_DELL_MEC5035
+ 
++config INTEL_GMA_DPLL_REF_FREQ
++	default 100000000
++
+ config MAINBOARD_DIR
+ 	default "dell/e6400"
+ 
+-- 
+2.45.1
+