[PATCH 3/3] ram: rk3399: Conduct memory training at 400MHz

[Lee Jones]

Currently the default initialisation frequency is 50MHz.  Although
this does appear to be suitable for some LPDDR4 RAM chips, training at
this low frequency has been seen to cause Column errors, leading to
Capacity check errors on others.

Here we force RAM initialisation to happen at 400MHz before ramping up
to the final value running value of 800MHz after everything has been
successfully configured.

Link: https://lore.kernel.org/u-boot/Yo4v3jUeHXTovjOH@google.com/
Suggested-by: YouMin Chen <cym at rock-chips.com>
Signed-off-by: Lee Jones <lee at kernel.org>
Tested-by: Xavier Drudis Ferran <xdrudis at tinet.cat>
Reviewed-by: Kever Yang <kever.yang at rock-chips.com>
---
 drivers/ram/rockchip/sdram_rk3399.c | 36 +++++++++++++++++------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/drivers/ram/rockchip/sdram_rk3399.c b/drivers/ram/rockchip/sdram_rk3399.c
index 34d6c93f95..b05c5925d5 100644
--- a/drivers/ram/rockchip/sdram_rk3399.c
+++ b/drivers/ram/rockchip/sdram_rk3399.c
@@ -85,7 +85,7 @@ struct sdram_rk3399_ops {
 	int (*data_training_first)(struct dram_info *dram, u32 channel, u8 rank,
 				   struct rk3399_sdram_params *sdram);
 	int (*set_rate_index)(struct dram_info *dram,
-			      struct rk3399_sdram_params *params);
+			      struct rk3399_sdram_params *params, u32 ctl_fn);
 	void (*modify_param)(const struct chan_info *chan,
 			     struct rk3399_sdram_params *params);
 	struct rk3399_sdram_params *
@@ -1644,7 +1644,8 @@ static int data_training_first(struct dram_info *dram, u32 channel, u8 rank,
 }
 
 static int switch_to_phy_index1(struct dram_info *dram,
-				struct rk3399_sdram_params *params)
+				struct rk3399_sdram_params *params,
+				u32 unused)
 {
 	u32 channel;
 	u32 *denali_phy;
@@ -2539,26 +2540,25 @@ static int lpddr4_set_ctl(struct dram_info *dram,
 }
 
 static int lpddr4_set_rate(struct dram_info *dram,
-			   struct rk3399_sdram_params *params)
+			    struct rk3399_sdram_params *params,
+			    u32 ctl_fn)
 {
-	u32 ctl_fn;
 	u32 phy_fn;
 
-	for (ctl_fn = 0; ctl_fn < 2; ctl_fn++) {
-		phy_fn = lpddr4_get_phy_fn(params, ctl_fn);
+	phy_fn = lpddr4_get_phy_fn(params, ctl_fn);
 
-		lpddr4_set_phy(dram, params, phy_fn, &dfs_cfgs_lpddr4[ctl_fn]);
-		lpddr4_set_ctl(dram, params, ctl_fn,
-			       dfs_cfgs_lpddr4[ctl_fn].base.ddr_freq);
+	lpddr4_set_phy(dram, params, phy_fn, &dfs_cfgs_lpddr4[ctl_fn]);
+	lpddr4_set_ctl(dram, params, ctl_fn,
+		       dfs_cfgs_lpddr4[ctl_fn].base.ddr_freq);
 
-		if (IS_ENABLED(CONFIG_RAM_ROCKCHIP_DEBUG))
-			printf("%s: change freq to %dMHz %d, %d\n", __func__,
-			       dfs_cfgs_lpddr4[ctl_fn].base.ddr_freq / MHz,
-			       ctl_fn, phy_fn);
-	}
+	if (IS_ENABLED(CONFIG_RAM_ROCKCHIP_DEBUG))
+		printf("%s: change freq to %dMHz %d, %d\n", __func__,
+		       dfs_cfgs_lpddr4[ctl_fn].base.ddr_freq / MHz,
+		       ctl_fn, phy_fn);
 
 	return 0;
 }
+
 #endif /* CONFIG_RAM_RK3399_LPDDR4 */
 
 /* CS0,n=1
@@ -2955,6 +2955,12 @@ static int sdram_init(struct dram_info *dram,
 		params->ch[ch].cap_info.rank = rank;
 	}
 
+#if defined(CONFIG_RAM_RK3399_LPDDR4)
+	/* LPDDR4 needs to be trained at 400MHz */
+	lpddr4_set_rate(dram, params, 0);
+	params->base.ddr_freq = dfs_cfgs_lpddr4[0].base.ddr_freq / MHz;
+#endif
+
 	params->base.num_channels = 0;
 	for (channel = 0; channel < 2; channel++) {
 		const struct chan_info *chan = &dram->chan[channel];
@@ -3005,7 +3011,7 @@ static int sdram_init(struct dram_info *dram,
 	params->base.stride = calculate_stride(params);
 	dram_all_config(dram, params);
 
-	ret = dram->ops->set_rate_index(dram, params);
+	ret = dram->ops->set_rate_index(dram, params, 1);
 	if (ret)
 		return ret;
 
-- 
2.37.1.559.g78731f0fdb-goog