Change in coreboot[master]: [WIP]soc/intel/cannonlake: Clear EMMC timeout for USB boot

[Bora Guvendik (Code Review)]

Bora Guvendik has uploaded this change for review. ( https://review.coreboot.org/25290

Change subject: [WIP]soc/intel/cannonlake: Clear EMMC timeout for USB boot
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[WIP]soc/intel/cannonlake: Clear EMMC timeout for USB boot

Clear EMMC timeout register to avoid EMMC issue according to cannonlake
bios writer guide. _PS0 is not called by OS during USB boot but OS still
initializes emmc. Add _INI to cover USB boot case.

BUG=b.71586766
TEST=Install OS into EMMC

Change-Id: I4eef23f637f781b709696951c5bd825530cc1d11
Signed-off-by: Bora Guvendik 
---
M src/soc/intel/cannonlake/acpi/scs.asl
1 file changed, 13 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/90/25290/1

diff --git a/src/soc/intel/cannonlake/acpi/scs.asl b/src/soc/intel/cannonlake/acpi/scs.asl
index 4062e70..7e9195a 100644
--- a/src/soc/intel/cannonlake/acpi/scs.asl
+++ b/src/soc/intel/cannonlake/acpi/scs.asl
@@ -31,6 +31,12 @@
    		PGEN, 1,	/* PG_ENABLE */
    	}

+		Method(_INI) {
+			/* Clear register 0x1C20/0x4820 */
+                        ^^PCRA (PID_EMMC, 0x1C20, 0x0)
+                        ^^PCRA (PID_EMMC, 0x4820, 0x0)
+		}
+
    	Method(_PS0, 0, Serialized) {
    		Stall (50) // Sleep 50 us

@@ -80,6 +86,13 @@
    		PGEN, 1,	/* PG_ENABLE */
    	}

+		Method(_INI)
+		{
+			/* Clear register 0x1C20/0x4820 */
+			^^PCRA (PID_SDX, 0x1C20, 0x0)
+			^^PCRA (PID_SDX, 0x4820, 0x0)
+		}
+
    	Method (_PS0, 0, Serialized)
    	{
    		Store (0, PGEN) /* Disable PG */