Change in coreboot[master]: mb/google/skyrim: Fix ESPI communication issues

[Karthik Ramasubramanian (Code Review)]

Karthik Ramasubramanian has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/63286 )

Change subject: mb/google/skyrim: Fix ESPI communication issues
......................................................................

mb/google/skyrim: Fix ESPI communication issues

* Use dedicated ALERT pin to resolve NO_RESPONSE error/status while
getting target configuration.
* Configure the ESPI to operate at 16 MHZ since operating at 33 MHz
causes boot stall.

BUG=b:226635441
TEST=Build and Boot to OS in Skyrim. Ensure that EC <-> AP communication
is working fine through Host Command debug logs in EC console, ectool
version command.

Signed-off-by: Karthikeyan Ramasubramanian 
Change-Id: I951afdada8ee4f917cdeba8e287e5a2ae77c97ee
---
M src/mainboard/google/skyrim/variants/baseboard/devicetree.cb
1 file changed, 2 insertions(+), 2 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/86/63286/1

diff --git a/src/mainboard/google/skyrim/variants/baseboard/devicetree.cb b/src/mainboard/google/skyrim/variants/baseboard/devicetree.cb
index 8fa6ba5..7f74d6d 100644
--- a/src/mainboard/google/skyrim/variants/baseboard/devicetree.cb
+++ b/src/mainboard/google/skyrim/variants/baseboard/devicetree.cb
@@ -27,9 +27,9 @@
    	},

.io_mode = ESPI_IO_MODE_QUAD,
-		.op_freq_mhz = ESPI_OP_FREQ_33_MHZ,
+		.op_freq_mhz = ESPI_OP_FREQ_16_MHZ,
    	.crc_check_enable = 1,
-		.alert_pin = ESPI_ALERT_PIN_IN_BAND,
+		.alert_pin = ESPI_ALERT_PIN_OPEN_DRAIN,
    	.periph_ch_en = 1,
    	.vw_ch_en = 1,
    	.oob_ch_en = 0,