[PATCH] FSL DDR: Errata A009942 clears board cpo_sample

[Joakim Tjernlund]

LSB in debug_28 register is cleared here so
previous setting by errata A009942 is lost.
Save and restore LSB in debug_28

Signed-off-by: Joakim Tjernlund <joakim.tjernlund at infinera.com>
---
 drivers/ddr/fsl/fsl_ddr_gen4.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/ddr/fsl/fsl_ddr_gen4.c b/drivers/ddr/fsl/fsl_ddr_gen4.c
index 31c58d9a8e..1f8ff87a8b 100644
--- a/drivers/ddr/fsl/fsl_ddr_gen4.c
+++ b/drivers/ddr/fsl/fsl_ddr_gen4.c
@@ -477,6 +477,8 @@ step2:
 #ifdef CONFIG_SYS_FSL_ERRATUM_A009942
 	ddr_freq = get_ddr_freq(ctrl_num) / 1000000;
 	val32 = ddr_in32(&ddr->debug[28]);
+	temp32 = val32 & 0xff;
+	debug("cpo_sample:%x\n", temp32);
 	val32 &= 0xff0fff00;
 	if (ddr_freq <= 1333)
 		val32 |= 0x0080006a;
@@ -487,6 +489,8 @@ step2:
 	else if (ddr_freq <= 2133)
 		val32 |= 0x0060007b;
 
+	if (temp32)
+		val32 = (val32 & ~0xff) | temp32;
 	ddr_out32(&ddr->debug[28], val32);
 	debug("Applied errata CONFIG_SYS_FSL_ERRATUM_A009942\n");
 #endif
-- 
2.43.2