tree 1a91cc80475a15916af9aba6a7a64e59b3524567
parent e70c9740033b5e3c82080bf25bcf510479374004
author Rex-BC Chen <rex-bc.chen@mediatek.com> 1647400407 +0800
committer Commit Bot <commit-bot@chromium.org> 1647901735 +0000

UPSTREAM: mb/google/corsola: Revise power-on sequence of PS8640

Although the panel initializes fine and the fw recovery screen is
displayed without issues, the current power-on sequence of the
PS8640 violates the spec of the PS8640, which can be confirmed by
measuring it with an oscilloscope.

The sequence is:
- set VDD12 to be 1.2V
- set VDD33 to be 3.3V
- pull hign PD#
- pull down RST#
- delay 2ms
- pull high RST#
- delay more than 50ms (55ms for margin)
- pull down RST#
- delay more than 50ms (55ms for margin)
- pull high RST#

This flow will increase 110ms if firmware display is enabled in
krabby. For normal booting flow, the firmware will not be enabled,
so it will meet boot time requirements of Chrome OS. (Less than 1s.)

Datasheet name: PS8640_DS_V1.4_20200210.docx.

BUG=b:222650141
TEST=show fw display normally in krabby.
TEST=result of waveform meets the spec.

Chapter: 14.
Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62893
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Original-Change-Id: I7706c56dc7fc13ac84c0d52a6e534bc0988e8fd3
GitOrigin-RevId: d6727ba9723be806713320a7ff19e5d5c3bd1d3f
Change-Id: Ib7794c11594e9d22080d4edf593e5ca82b04ff80
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/coreboot/+/3539521
Tested-by: CopyBot Service Account <copybot.service@gmail.com>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>