[PATCH 10/18] EDAC/synopsys: Get corrected bit position

[Serge Semin]

Since the DQ-bus width is now available in the driver we can use it to
calculate the bit-position corrected by the ECC engine. It can be done
based on the offsets provided in the table [1]. Using info from that table
let's introduce a new inline method snps_get_bitpos() which would provide
the actual CE bit-position based on the value read from the
ECCSTAT.corrected_bit_num field and the DQ-bus width. The method will be
called if a corrected error is detected.

[1] DesignWare® Cores Enhanced Universal DDR Memory Controller (uMCTL2)
    Databook, Version 3.91a, October 2020, p.426-427

Signed-off-by: Serge Semin <Sergey.Semin at baikalelectronics.ru>
---
 drivers/edac/synopsys_edac.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/edac/synopsys_edac.c b/drivers/edac/synopsys_edac.c
index af34a83dc1ef..5a116c9ebeda 100644
--- a/drivers/edac/synopsys_edac.c
+++ b/drivers/edac/synopsys_edac.c
@@ -10,6 +10,7 @@
 #include <linux/bitfield.h>
 #include <linux/edac.h>
 #include <linux/fs.h>
+#include <linux/log2.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/seq_file.h>
@@ -357,6 +358,27 @@ struct snps_edac_priv {
 #endif
 };
 
+/**
+ * snps_get_bitpos - Get DQ-bus corrected bit position.
+ * @bitnum:	Bit number retrieved from the ECCSTAT.corrected_bit_num field.
+ * @dq_width:	Controller DQ-bus width.
+ *
+ * Return: actual corrected DQ-bus bit position starting from 0.
+ */
+static inline u32 snps_get_bitpos(u32 bitnum, enum snps_dq_width dq_width)
+{
+	/* ecc[0] bit */
+	if (bitnum == 0)
+		return BITS_PER_BYTE << dq_width;
+
+	/* ecc[1:x] bit */
+	if (is_power_of_2(bitnum))
+		return (BITS_PER_BYTE << dq_width) + ilog2(bitnum) + 1;
+
+	/* data[0:y] bit */
+	return bitnum - ilog2(bitnum) - 2;
+}
+
 /**
  * snps_get_error_info - Get the current ECC error info.
  * @priv:	DDR memory controller private instance data.
@@ -385,6 +407,8 @@ static int snps_get_error_info(struct snps_edac_priv *priv)
 	if (!p->ce_cnt)
 		goto ue_err;
 
+	p->ceinfo.bitpos = snps_get_bitpos(p->ceinfo.bitpos, priv->info.dq_width);
+
 	regval = readl(base + ECC_CEADDR0_OFST);
 	p->ceinfo.row = FIELD_GET(ECC_CEADDR0_ROW_MASK, regval);
 
-- 
2.35.1