mb/google/zork: Reconfigure PCIE_RST1_L as GPO driven low on sleep path
This change configures PCIE_RST1_L as GPO driven low on the sleep
path. This is required to keep PERST# asserted to devices until
coreboot deasserts it on S3 resume path. Without this change, on S3
resume, PCIE_RST1_L gets deasserted sooner than required resulting in
violation of PCIe reset timings.
With this change, the behavior of PCIE_RST1_L is as follows:
1. GPIO27 is configured as NF (PCIE_RST1_L) in coreboot
bootblock/romstage and driven high.
2. On S3 entry, GPIO27 is configured as GPO driven low.
* Boot out of G3: Timing should be met since GPIO_27 is pulled down by
default until coreboot configures it.
* S3 resume: Timing should be met since GPIO_27 is configured as GPO
low and it retains state across S3 entry/exit. So, should be low
until coreboot configures it.
* Warm reset: Timing should be met since it is configured as NF. So,
hardware guarantees the reset timing as seen in "warm reset.jpg" in
#46.
BUG=b:152582706
Signed-off-by: Furquan Shaikh <furquan@google.com>
Change-Id: Ia0ad1522edc438fd054d927ef4a2ab5c27329c00
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/coreboot/+/2261116
Reviewed-by: Aaron Durbin <adurbin@google.com>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
diff --git a/src/mainboard/google/zork/variants/baseboard/gpio_baseboard_common.c b/src/mainboard/google/zork/variants/baseboard/gpio_baseboard_common.c
index e43b0b4..1dd2dd5 100644
--- a/src/mainboard/google/zork/variants/baseboard/gpio_baseboard_common.c
+++ b/src/mainboard/google/zork/variants/baseboard/gpio_baseboard_common.c
@@ -34,6 +34,8 @@
static const struct soc_amd_gpio gpio_sleep_table[] = {
/* PEN_POWER_EN */
PAD_GPO(GPIO_5, LOW),
+ /* PCIE_RST1_L */
+ PAD_GPO(GPIO_27, LOW),
/* EN_PWR_CAMERA */
PAD_GPO(GPIO_76, LOW),
};
