drivers/analogix/anx7625: Fix edid_read()

The current implementations of edid_read() and segments_edid_read() have
a few problems:

1. The type of variable `c` is incorrect, not matching the return type
   of sp_tx_aux_rd(). In addition, the meaning of `c` is unknown.
2. It is pointless to do `cnt++` when sp_tx_aux_rd() fails.
3. These two functions ignore the return value of
   anx7625_reg_block_read().
4. In segments_edid_read(), anx7625_reg_write() might return a positive
   value on failure.

Fix all of the 4 issues, and modify the code to be closer to kernel
5.10's implementation (drivers/gpu/drm/bridge/analogix/anx7625.c). Note
that, however, unlike in kernel, anx7625_reg_block_read() here doesn't
return the number of bytes. On success, 0 is returned instead.

In addition, following coreboot's convention, always return negative
error codes. In particular, change the return value to -1 for
edid_read() and segments_edid_read() on failure.

BUG=b:207055969
TEST=emerge-asurada coreboot
BRANCH=none

Change-Id: Ife9d7d97df2926b4581ba519a152c9efed8cd969
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59540
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

0 files changed, 0 insertions, 0 deletions