[S] Change in coreboot[master]: mb/lenovo/x200: Read EDID in mainboard_vbt_filename()

[Bill XIE (Code Review)]

Attention is currently required from: Stefan Ott, Alexander Couzens.

Bill XIE has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/74181 )

Change subject: mb/lenovo/x200: Read EDID in mainboard_vbt_filename()
......................................................................

mb/lenovo/x200: Read EDID in mainboard_vbt_filename()

mainboard_vbt_filename() used to assume that it is called after a call
to get_blc_pwm_freq_value() with a valid parameter, but currently it
is the first call of get_blc_pwm_freq_value(NULL), and will return 0,
making "data_led.vbt" is always returned, regardless of the actual
type of the panel.

Combined with the previous commit, in this commit
mainboard_vbt_filename() will explicitly read EDID string via
get_edid_str() and use this string to call get_blc_pwm_freq_value().

This will resolve https://ticket.coreboot.org/issues/475 .

Signed-off-by: Bill XIE 
Change-Id: I2e080b29321b6989d1f26b6c67876b3d703042f4
---
M src/mainboard/lenovo/x200/blc.c
1 file changed, 25 insertions(+), 3 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/81/74181/1

diff --git a/src/mainboard/lenovo/x200/blc.c b/src/mainboard/lenovo/x200/blc.c
index ef2dbb1..02b16d1 100644
--- a/src/mainboard/lenovo/x200/blc.c
+++ b/src/mainboard/lenovo/x200/blc.c
@@ -4,6 +4,7 @@
 #include <commonlib/helpers.h>
 #include <console/console.h>
 #include <northbridge/intel/gm45/gm45.h>
+#include <device/pci.h>
 #include <drivers/intel/gma/opregion.h>

static const struct blc_pwm_t blc_entries[] = {
@@ -36,9 +37,8 @@

const char *mainboard_vbt_filename(void)
 {
-	u16 pwm_freq;
-
-	pwm_freq = get_blc_pwm_freq_value(NULL);
+	struct device *gma = pcidev_path_on_root(PCI_DEVFN(0x2, 0));
+	u16 pwm_freq = gma ? get_blc_pwm_freq_value(get_edid_str(gma)) : 0;

if (pwm_freq == 0) {
    	printk(BIOS_DEBUG,