[PATCH v4 18/18] EDAC/synopsys: Add mapping-based memory size calculation

[Serge Semin <fancer.lancer@gmail.com>]

Currently the size of the memory attached to the controller is retrieved
by means of the si_meminfo() method. It isn't quite correct because the
system may have more than one memory controller. There is a better and
more portable approach available to find out the attached memory size.
Since the full HIF/SDRAM mapping table is available already in the device
probe procedure and the DQ-bus width is detected at that stage too, that
info can be used to calculate the total memory size accessible over the
corresponding DW uMCTL2 DDR controller. It can be done since the
controller databook demands that none two SDRAM bits are mapped to the
same HIF bit [1] and that the unused SDRAM address bits mapping must be
disabled [2].

Note the size calculation procedure takes the ranks mapping into account.
That part will be removed after the multi-ranked MC registration is added.

[1] DesignWare® Cores Enhanced Universal DDR Memory Controller (uMCTL2)
    Databook, Version 3.91a, October 2020, p.108
[2] DesignWare® Cores Enhanced Universal DDR Memory Controller (uMCTL2)
    Databook, Version 3.91a, October 2020, p.109

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
---
 drivers/edac/synopsys_edac.c | 66 ++++++++++++++++++++++++++----------
 1 file changed, 49 insertions(+), 17 deletions(-)

diff --git a/drivers/edac/synopsys_edac.c b/drivers/edac/synopsys_edac.c
index d67a19fedb3c..9a621b7a256d 100644
--- a/drivers/edac/synopsys_edac.c
+++ b/drivers/edac/synopsys_edac.c
@@ -965,20 +965,6 @@ static inline enum dev_type snps_get_dtype(u32 mstr)
 	return DEV_UNKNOWN;
 }
 
-/**
- * snps_get_memsize - Read the size of the attached memory device.
- *
- * Return: the memory size in bytes.
- */
-static u32 snps_get_memsize(void)
-{
-	struct sysinfo inf;
-
-	si_meminfo(&inf);
-
-	return inf.totalram * inf.mem_unit;
-}
-
 /**
  * snps_get_mtype - Returns controller memory type.
  * @mstr:	Master CSR value.
@@ -1393,6 +1379,51 @@ static void snps_get_addr_map(struct snps_edac_priv *priv)
 	snps_get_hif_rank_map(priv, regval);
 }
 
+/**
+ * snps_get_sdram_size - Calculate SDRAM size.
+ * @priv:	DDR memory controller private data.
+ *
+ * The total size of the attached memory is calculated based on the HIF/SDRAM
+ * mapping table. It can be done since the hardware reference manual demands
+ * that none two SDRAM bits should be mapped to the same HIF bit and that the
+ * unused SDRAM address bits mapping must be disabled.
+ *
+ * Return: the memory size in bytes.
+ */
+static u64 snps_get_sdram_size(struct snps_edac_priv *priv)
+{
+	struct snps_hif_sdram_map *map = &priv->hif_sdram_map;
+	u64 size = 0;
+	int i;
+
+	for (i = 0; i < DDR_MAX_ROW_WIDTH; i++) {
+		if (map->row[i] != DDR_ADDRMAP_UNUSED)
+			size++;
+	}
+
+	for (i = 0; i < DDR_MAX_COL_WIDTH; i++) {
+		if (map->col[i] != DDR_ADDRMAP_UNUSED)
+			size++;
+	}
+
+	for (i = 0; i < DDR_MAX_BANK_WIDTH; i++) {
+		if (map->bank[i] != DDR_ADDRMAP_UNUSED)
+			size++;
+	}
+
+	for (i = 0; i < DDR_MAX_BANKGRP_WIDTH; i++) {
+		if (map->bankgrp[i] != DDR_ADDRMAP_UNUSED)
+			size++;
+	}
+
+	for (i = 0; i < DDR_MAX_RANK_WIDTH; i++) {
+		if (map->rank[i] != DDR_ADDRMAP_UNUSED)
+			size++;
+	}
+
+	return 1ULL << (size + priv->info.dq_width);
+}
+
 /**
  * snps_init_csrows - Initialize the csrow data.
  * @mci:	EDAC memory controller instance.
@@ -1405,7 +1436,8 @@ static void snps_init_csrows(struct mem_ctl_info *mci)
 	struct snps_edac_priv *priv = mci->pvt_info;
 	struct csrow_info *csi;
 	struct dimm_info *dimm;
-	u32 size, row, width;
+	u32 row, width;
+	u64 size;
 	int j;
 
 	/* Actual SDRAM-word width for which ECC is calculated */
@@ -1413,13 +1445,13 @@ static void snps_init_csrows(struct mem_ctl_info *mci)
 
 	for (row = 0; row < mci->nr_csrows; row++) {
 		csi = mci->csrows[row];
-		size = snps_get_memsize();
+		size = snps_get_sdram_size(priv);
 
 		for (j = 0; j < csi->nr_channels; j++) {
 			dimm		= csi->channels[j]->dimm;
 			dimm->edac_mode	= EDAC_SECDED;
 			dimm->mtype	= priv->info.sdram_mode;
-			dimm->nr_pages	= (size >> PAGE_SHIFT) / csi->nr_channels;
+			dimm->nr_pages	= PHYS_PFN(size) / csi->nr_channels;
 			dimm->grain	= width;
 			dimm->dtype	= priv->info.dev_cfg;
 		}
-- 
2.41.0