tree 1d0ace21886d83a8ffffbdc72d66d93abd69e916
parent 8998ab8b020d6711f56634880b26b2b908d1340c
author Michael Niewöhner <foss@mniewoehner.de> 1655752947 +0200
committer Michael Niewöhner <foss@mniewoehner.de> 1667423232 +0000

mb/clevo/l140mu: work around PECI staying high when idle, blocking s0ix

According to Intel doc# 575683 the PECI bus should be low when idle and
is pulled up by clients with strong drive. However, for unknown reasons
the bus stays high on this board, blocking s0ix entry.

The PECI reference schematic in the ASPEED AST2400 BMC datasheet
(actually not related to this board) says that a pull-down is *required*
for the idle state.

This might be just a requirement of this BMC, since this is nowhere
documented in Intel datasheets, schematics or elsewhere. However,
configuring a weak pull-down (20 k) on the PECI pad indeed solves this
problem for now.

Change-Id: I85193000af67cd2c0465bdbb58cdd51b68fd5b4f
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68794
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>