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 <persmule@hardenedlinux.org>
Change-Id: I2e080b29321b6989d1f26b6c67876b3d703042f4
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74181
Reviewed-by: Swift Geek (Sebastian Grzywna) <swiftgeek@gmail.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <felixsinger@posteo.net>

0 files changed, 0 insertions, 0 deletions