[coreboot-gerrit] Change in coreboot[master]: mb/google/zork/variants/dalboz: Use HS200 for eMMC

[Furquan Shaikh (Code Review)]

Furquan Shaikh has submitted this change. ( https://review.coreboot.org/c/coreboot/+/43572 )

Change subject: mb/google/zork/variants/dalboz: Use HS200 for eMMC
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mb/google/zork/variants/dalboz: Use HS200 for eMMC

Earlier versions of Dalboz did not correctly handle HS400. One fix was
to add stitching vias, but these boards did not have them. b/156539551

Another possible fix is to add tuning parameters including drive
strength, but that is still a WIP. b/158959725

This should correct OS load failures in the meantime by running the bus
slower.

BUG=b:158845662
TEST=build, flash, boot sku 0x5a80000c to OS
BRANCH=None
Signed-off-by: Eric Peers 
Change-Id: Ia3e7a641bde04c5a7be29bf91c38dd8c110ed17a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43572
Reviewed-by: Angel Pons 
Reviewed-by: Raul Rangel 
Tested-by: build bot (Jenkins) 
---
M src/mainboard/google/zork/variants/dalboz/variant.c
1 file changed, 14 insertions(+), 2 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Raul Rangel: Looks good to me, approved
  Angel Pons: Looks good to me, approved

diff --git a/src/mainboard/google/zork/variants/dalboz/variant.c b/src/mainboard/google/zork/variants/dalboz/variant.c
index 0212161..de4338e 100644
--- a/src/mainboard/google/zork/variants/dalboz/variant.c
+++ b/src/mainboard/google/zork/variants/dalboz/variant.c
@@ -127,9 +127,21 @@
    cfg = config_of_soc();

if (sku_has_emmc()) {
-		if (sku_id() == 0x5A800003)
-			/* rev0 boards have issues with HS400 */
+		if ((sku_id() == 0x5A800003) || (sku_id() == 0x5A80000C)) {
+			/*
+			 * rev0 and rev1 boards have issues with HS400
+			 *
+			 * There is a tuning fix with ES which shows promise
+			 * for some boards, and a HW fix with stitching vias.
+			 * There were also concerns that these boards did not
+			 * have good margins for certain skus.
+			 *
+			 * But these original boards have none of these fixes.
+			 * So we keep the speed low here, with the intent that
+			 * other variants implement these corrections.
+			 */
    		cfg->sd_emmc_config = SD_EMMC_EMMC_HS200;
+		}
    } else {
    	cfg->sd_emmc_config = SD_EMMC_DISABLE;
    }