[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, Bill XIE, Alexander Couzens.

Hello Stefan Ott, build bot (Jenkins), Angel Pons, Arthur Heymans, Alexander Couzens, Swift Geek (Sebastian Grzywna),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/74181

to look at the new patch set (#8).

Change subject: mb/lenovo/x200: Read EDID in mainboard_vbt_filename()
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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,
so "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
gm45_get_lvds_edid_str() and use this string to call
get_blc_pwm_freq_value().

Resolves: https://ticket.coreboot.org/issues/475

Tested on my x200s with LTD121EQ3B (LED), and x200 with LTD121EWVB
(CCFL).

Signed-off-by: Bill XIE 
Change-Id: I2e080b29321b6989d1f26b6c67876b3d703042f4
---
M src/mainboard/lenovo/x200/blc.c
1 file changed, 29 insertions(+), 3 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/81/74181/8