From d2b2be39296d910178173273017800a1b054a1ba Mon Sep 17 00:00:00 2001
From: Kane Chen <kane.chen@intel.com>
Date: Mon, 13 Apr 2020 20:48:54 +0800
Subject: soc/intel/cannonlake: Report driver strength by _DSM in eMMC ACPI
 device

According to doc 621880, it suggests setting 40 ohm in byte 185 in extCSD.

This commit provides _DSM method for driver to query driving strength.

TEST=mmc extcsd read |grep HS_TIMING and found bit[7:4] is set to 4
BUG=b:154159888

Signed-off-by: Kane Chen <kane.chen@intel.com>
Change-Id: I1b4df8b0d1d2cad3a7f521ad47ee5a4b3320c767
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40467
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
---
 src/soc/intel/cannonlake/acpi/scs.asl | 56 +++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

(limited to 'src/soc/intel/cannonlake')

diff --git a/src/soc/intel/cannonlake/acpi/scs.asl b/src/soc/intel/cannonlake/acpi/scs.asl
index 775c99781a..8dd3003053 100644
--- a/src/soc/intel/cannonlake/acpi/scs.asl
+++ b/src/soc/intel/cannonlake/acpi/scs.asl
@@ -20,9 +20,12 @@ Scope (\_SB.PCI0) {
 		Name(_ADR, 0x001A0000)
 		Name (_DDN, "eMMC Controller")
 		Name (TEMP, 0)
+		Name (DSUU, ToUUID("f6c13ea5-65cd-461f-ab7a-29f7e8d5bd61"))
 
 		OperationRegion(SCSR, PCI_Config, 0x00, 0x100)
 		Field(SCSR, WordAcc, NoLock, Preserve) {
+			Offset (0x0),	/* PCI VID DID */
+			VDID, 32,
 			Offset (0x84),	/* PMECTRLSTATUS */
 			PMCR, 16,
 			Offset (0xA2),	/* PG_CONFIG */
@@ -64,6 +67,59 @@ Scope (\_SB.PCI0) {
 				Return (0)
 			}
 		}
+		/* _DSM x86 Device Specific Method
+		 * Arg0: UUID Unique function identifier
+		 * Arg1: Integer Revision Level
+		 * Arg2: Integer Function Index (0 = Return Supported Functions)
+		 * Arg3: Package Parameters
+		 */
+		Method (_DSM, 4)
+		{
+			If (LEqual (Arg0, ^DSUU)) {
+				/* Check the revision */
+				If (LGreaterEqual (Arg1, Zero)) {
+					/*
+					 * Function Index 0 the return value is a buffer
+					 * containing one bit for each function index, starting
+					 * with zero.
+					 * Bit 0 - Indicates whether there is support for any
+					 * 	   functions other than function 0
+					 * Bit 1 - Indicates support to clear power control
+					 *	   register
+					 * Bit 2 - Indicates support to set power control
+					 *	   register
+					 * Bit 3 - Indicates support to set 1.8V signalling
+					 * Bit 4 - Indicates support to set 3.3V signalling
+					 * Bit 5 - Indicates support for HS200 mode
+					 * Bit 6 - Indicates support for HS400 mode
+					 * Bit 9 - Indicates eMMC I/O Driver Strength
+					 */
+					If (LEqual (Arg2, Zero)) {
+						If (Lequal (VDID, 0x02c48086) ) {
+							/*
+							 * Set bit 9 for CML eMMC to indicate
+							 * eMMC I/O driver strength is supported
+							 */
+							Return(Buffer() {0x0, 0x02})
+						}
+
+					}
+					/*
+					 * Function Index 9, the return value is preferred eMMC
+					 * driver strength
+					 * 0 - 50 ohm
+					 * 1 - 33 ohm
+					 * 2 - 66 ohm
+					 * 3 - 100 ohm
+					 * 4 - 40 ohm
+					 */
+					If (LEqual (Arg2, 9)) {
+						Return(Buffer() {0x4})
+					}
+				}
+			}
+			Return(Buffer() { 0x0 })
+		}
 	}
 
 	/* SD CARD */
-- 
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