[PATCH v2 06/15] EDAC/synopsys: Add optional ECC Scrub support

[Serge Semin]

DW uMCTL2 DDRC ECC has a so called ECC Scrub feature in case if an
single-bit error is detected. The scrub is executed as a new RMW operation
to the location that resulted in a single-bit error thus fixing the ECC
code preserved in the SDRAM. But that feature not only optional, but also
runtime switchable. So there can be platforms with DW uMCTL2 DDRC not
supporting hardware-base scrub. In those cases the single-bit errors will
still be detected but won't be fixed until the next SDRAM write commands
to the erroneous location. Since the ECC Scrub feature availability is
detectable by means of the ECCCFG0.dis_scrub flag state we can use it to
tune the MCI core up so one would automatically execute the
platform-specific the platform-specific scrubbing to the affected SDRAM
location. It's now possible to be done since the DW uMCTL2 DDRC driver
supports the actual system address reported to the MCI core. The only
thing left to do is to auto-detect the ECC Scrub feature availability and
set the mem_ctl.info.scrub_mode mode with SCRUB_SW_SRC if the feature is
unavailable. The rest will be done by the MCI core when the single-bit
errors happen.

Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/edac/synopsys_edac.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/edac/synopsys_edac.c b/drivers/edac/synopsys_edac.c
index d5d82531719b..b36f7ec4a79e 100644
--- a/drivers/edac/synopsys_edac.c
+++ b/drivers/edac/synopsys_edac.c
@@ -32,6 +32,7 @@
 #define SNPS_EDAC_MOD_VER		"1"
 
 /* DDR capabilities */
+#define SNPS_CAP_ECC_SCRUB		BIT(0)
 #define SNPS_CAP_ZYNQMP			BIT(31)
 
 /* Synopsys uMCTL2 DDR controller registers that are relevant to ECC */
@@ -114,6 +115,7 @@
 #define DDR_MSTR_MEM_LPDDR4		BIT(5)
 
 /* ECC CFG0 register definitions */
+#define ECC_CFG0_DIS_SCRUB		BIT(4)
 #define ECC_CFG0_MODE_MASK		GENMASK(2, 0)
 
 /* ECC status register definitions */
@@ -1008,6 +1010,10 @@ static int snps_get_ddrc_info(struct snps_edac_priv *priv)
 		return -ENXIO;
 	}
 
+	/* Assume HW-src scrub is always available if it isn't disabled */
+	if (!(regval & ECC_CFG0_DIS_SCRUB))
+		priv->info.caps |= SNPS_CAP_ECC_SCRUB;
+
 	/* Auto-detect the basic HIF/SDRAM bus parameters */
 	regval = readl(priv->baseaddr + DDR_MSTR_OFST);
 
@@ -1484,8 +1490,14 @@ static struct mem_ctl_info *snps_mc_create(struct snps_edac_priv *priv)
 			 MEM_FLAG_DDR3 | MEM_FLAG_LPDDR3 |
 			 MEM_FLAG_DDR4 | MEM_FLAG_LPDDR4;
 	mci->edac_ctl_cap = EDAC_FLAG_NONE | EDAC_FLAG_SECDED;
-	mci->scrub_cap = SCRUB_FLAG_HW_SRC;
-	mci->scrub_mode = SCRUB_NONE;
+
+	if (priv->info.caps & SNPS_CAP_ECC_SCRUB) {
+		mci->scrub_mode = SCRUB_HW_SRC;
+		mci->scrub_cap = SCRUB_FLAG_HW_SRC;
+	} else {
+		mci->scrub_mode = SCRUB_SW_SRC;
+		mci->scrub_cap = SCRUB_FLAG_SW_SRC;
+	}
 
 	mci->edac_cap = EDAC_FLAG_SECDED;
 	mci->ctl_name = "snps_umctl2_ddrc";
@@ -1578,6 +1590,8 @@ static int snps_ddrc_info_show(struct seq_file *s, void *data)
 
 	seq_puts(s, "Caps:");
 	if (priv->info.caps) {
+		if (priv->info.caps & SNPS_CAP_ECC_SCRUB)
+			seq_puts(s, " +Scrub");
 		if (priv->info.caps & SNPS_CAP_ZYNQMP)
 			seq_puts(s, " +ZynqMP");
 	} else {
-- 
2.37.2