soc/intel/apollolake: Disable Periodic Retraining per-SKU

Certain LPDDR4 models have some HW issues that can be worked around
by turning off Periodic Retraining feature in the memory controller.
Add option to disable PR per SKU.

BUG=chrome-os-partner:55466
TEST=run RMT test, pass

Change-Id: Ie7aa79586665f6d3a7edd854a9eef07e6a1b2ab8
Signed-off-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-on: https://review.coreboot.org/16320
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/mainboard/google/reef/romstage.c

@@ -103,6 +103,7 @@ static const struct lpddr4_sku skus[] = {
 		.ch0_dual_rank = 1,
 		.ch1_dual_rank = 1,
 		.part_num = "MT53B512M32D2NP",
+		.disable_periodic_retraining = 1,
 	},
 	/* MT53B256M32D1NP-062 WT:C - both logical channels */
 	[3] = {
@@ -110,6 +111,7 @@ static const struct lpddr4_sku skus[] = {
 		.ch0_rank_density = LP4_8Gb_DENSITY,
 		.ch1_rank_density = LP4_8Gb_DENSITY,
 		.part_num = "MT53B256M32D1NP",
+		.disable_periodic_retraining = 1,
 	},
 	/* K4F8E304HB-MGCH - both logical channels */
 	[PROTO_SKU] = {

src/soc/intel/apollolake/include/soc/meminit.h

@@ -102,6 +102,7 @@ struct lpddr4_sku {
 	int ch0_dual_rank;
 	int ch1_dual_rank;
 	const char *part_num;
+	bool disable_periodic_retraining;
 };
 
 struct lpddr4_cfg {

src/soc/intel/apollolake/meminit.c

@@ -254,6 +254,8 @@ void meminit_lpddr4_by_sku(struct FSP_M_CONFIG *cfg,
 						sku->ch1_dual_rank,
 						lpcfg->swizzle_config);
 	}
+
+	cfg->PeriodicRetrainingDisable = sku->disable_periodic_retraining;
 }
 
 void save_lpddr4_dimm_info(const struct lpddr4_cfg *lp4cfg, size_t mem_sku)