nb/intel/sandybridge: Use one sequence for write leveling

In order to run a write leveling test, one needs to unset the Qoff bit
in MR1, then run the test, and finally set Qoff again. The current IOSAV
sequence uses two subsequences to perform the test, while the other two
are unused. It is possible to perform the two necessary MR1 updates in
the same sequence, which can potentially improve runtime (not measured).

Since `write_mrreg` is no longer used, it is necessary to handle address
mirroring explicitly. This can be accomplished with the recently-added
`ddr3_mirror_mrreg` function, which is also used in `write_mrreg`.

Tested on Asus P8H61-M PRO, still boots.

Change-Id: I65ca1aa32cdb177d2a9e27c3b02e74ac0c882794
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47614
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 48 insertions, 8 deletions

diff --git a/src/northbridge/intel/sandybridge/raminit_common.c b/src/northbridge/intel/sandybridge/raminit_common.c
index 885689c94f..92d0c4f47d 100644
--- a/src/northbridge/intel/sandybridge/raminit_common.c
+++ b/src/northbridge/intel/sandybridge/raminit_common.c
@@ -1696,15 +1696,40 @@ static void precharge(ramctr_timing *ctrl)
 
 static void test_timB(ramctr_timing *ctrl, int channel, int slotrank)
 {
-	/* enable DQs on this slotrank */
-	write_mrreg(ctrl, channel, slotrank, 1, make_mr1(ctrl, slotrank, channel) | 1 << 7);
+	/* First DQS/DQS# rising edge after write leveling mode is programmed */
+	const u32 tWLMRD = 40;
+
+	u32 mr1reg = make_mr1(ctrl, slotrank, channel) | 1 << 7;
+	int bank = 1;
+
+	if (ctrl->rank_mirror[channel][slotrank])
+		ddr3_mirror_mrreg(&bank, &mr1reg);
 
 	wait_for_iosav(channel);
 
 	const struct iosav_ssq sequence[] = {
-		/* DRAM command NOP */
+		/* DRAM command MRS: enable DQs on this slotrank */
 		[0] = {
 			.sp_cmd_ctrl = {
+				.command    = IOSAV_MRS,
+				.ranksel_ap = 1,
+			},
+			.subseq_ctrl = {
+				.cmd_executions = 1,
+				.cmd_delay_gap  = 3,
+				.post_ssq_wait  = tWLMRD,
+				.data_direction = SSQ_NA,
+			},
+			.sp_cmd_addr = {
+				.address = mr1reg,
+				.rowbits = 6,
+				.bank    = bank,
+				.rank    = slotrank,
+			},
+		},
+		/* DRAM command NOP */
+		[1] = {
+			.sp_cmd_ctrl = {
 				.command    = IOSAV_NOP,
 				.ranksel_ap = 1,
 			},
@@ -1722,7 +1747,7 @@ static void test_timB(ramctr_timing *ctrl, int channel, int slotrank)
 			},
 		},
 		/* DRAM command NOP */
-		[1] = {
+		[2] = {
 			.sp_cmd_ctrl = {
 				.command    = IOSAV_NOP_ALT,
 				.ranksel_ap = 1,
@@ -1740,6 +1765,25 @@ static void test_timB(ramctr_timing *ctrl, int channel, int slotrank)
 				.rank    = slotrank,
 			},
 		},
+		/* DRAM command MRS: disable DQs on this slotrank */
+		[3] = {
+			.sp_cmd_ctrl = {
+				.command    = IOSAV_MRS,
+				.ranksel_ap = 1,
+			},
+			.subseq_ctrl = {
+				.cmd_executions = 1,
+				.cmd_delay_gap  = 3,
+				.post_ssq_wait  = ctrl->tMOD,
+				.data_direction = SSQ_NA,
+			},
+			.sp_cmd_addr = {
+				.address = mr1reg | 1 << 12,
+				.rowbits = 6,
+				.bank    = bank,
+				.rank    = slotrank,
+			},
+		},
 	};
 	iosav_write_sequence(channel, sequence, ARRAY_SIZE(sequence));
 
@@ -1747,10 +1791,6 @@ static void test_timB(ramctr_timing *ctrl, int channel, int slotrank)
 	iosav_run_once(channel);
 
 	wait_for_iosav(channel);
-
-	/* disable DQs on this slotrank */
-	write_mrreg(ctrl, channel, slotrank, 1,
-		make_mr1(ctrl, slotrank, channel) | 1 << 12 | 1 << 7);
 }
 
 static int discover_timB(ramctr_timing *ctrl, int channel, int slotrank)