[PATCH v5 2/2] EDAC: add EDAC driver for DMC520

[PATCH v5 2/2] EDAC: add EDAC driver for DMC520

[Lei Wang]

New driver supports error detection and correction on the devices with ARM
DMC-520 memory controller.

Signed-off-by: Lei Wang <leiwang_git@outlook.com>
Reviewed-by: James Morse <james.morse@arm.com>
---
    Changes in v5:
        - When enable configured interrupts, do not potentially disable
          other irrelevant interrupts.
        - fix return type of dmc520_get_scrub_type to enum scrub_type
        - Use capital letters for enum
        - Retrieve memory width from dmc register format_control
        - use cheaper spin_lock API.
        - Remove compatible line for "brcm,dmc-520"
        - Add James' Reviewed-by
---
 MAINTAINERS                |   6 +
 drivers/edac/Kconfig       |   7 +
 drivers/edac/Makefile      |   1 +
 drivers/edac/dmc520_edac.c | 632 +++++++++++++++++++++++++++++++++++++
 4 files changed, 646 insertions(+)
 create mode 100644 drivers/edac/dmc520_edac.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 77eae44bf5de..7c1ac8bc8ea1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5703,6 +5703,12 @@ F:	Documentation/driver-api/edac.rst
 F:	drivers/edac/
 F:	include/linux/edac.h
 
+EDAC-DMC520
+M:	Lei Wang <lewan@microsoft.com>
+L:	linux-edac@vger.kernel.org
+S:	Supported
+F:	drivers/edac/dmc520_edac.c
+
 EDAC-E752X
 M:	Mark Gross <mark.gross@intel.com>
 L:	linux-edac@vger.kernel.org
diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
index 200c04ce5b0e..7fde5aea0c1a 100644
--- a/drivers/edac/Kconfig
+++ b/drivers/edac/Kconfig
@@ -510,4 +510,11 @@ config EDAC_ASPEED
 	  First, ECC must be configured in the bootloader. Then, this driver
 	  will expose error counters via the EDAC kernel framework.
 
+config EDAC_DMC520
+       tristate "ARM DMC-520 ECC"
+       depends on ARM64
+       help
+         Support for error detection and correction on the
+         SoCs with ARM DMC-520 DRAM controller.
+
 endif # EDAC
diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
index 165ca65e1a3a..e0d98f5b2045 100644
--- a/drivers/edac/Makefile
+++ b/drivers/edac/Makefile
@@ -85,3 +85,4 @@ obj-$(CONFIG_EDAC_XGENE)		+= xgene_edac.o
 obj-$(CONFIG_EDAC_TI)			+= ti_edac.o
 obj-$(CONFIG_EDAC_QCOM)			+= qcom_edac.o
 obj-$(CONFIG_EDAC_ASPEED)		+= aspeed_edac.o
+obj-$(CONFIG_EDAC_DMC520)		+= dmc520_edac.o
diff --git a/drivers/edac/dmc520_edac.c b/drivers/edac/dmc520_edac.c
new file mode 100644
index 000000000000..aeb8d84405cf
--- /dev/null
+++ b/drivers/edac/dmc520_edac.c
@@ -0,0 +1,632 @@
+// SPDX-License-Identifier: GPL-2.0
+/* EDAC driver for DMC-520 */
+
+
+#include <linux/bitfield.h>
+#include <linux/edac.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include "edac_mc.h"
+
+/* DMC-520 registers */
+#define REG_OFFSET_FEATURE_CONFIG		0x130
+#define REG_OFFSET_ECC_ERRC_COUNT_31_00		0x158
+#define REG_OFFSET_ECC_ERRC_COUNT_63_32		0x15C
+#define REG_OFFSET_ECC_ERRD_COUNT_31_00		0x160
+#define REG_OFFSET_ECC_ERRD_COUNT_63_32		0x164
+#define REG_OFFSET_INTERRUPT_CONTROL		0x500
+#define REG_OFFSET_INTERRUPT_CLR		0x508
+#define REG_OFFSET_INTERRUPT_STATUS		0x510
+#define REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_31_00	0x528
+#define REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_63_32	0x52C
+#define REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_31_00	0x530
+#define REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_63_32	0x534
+#define REG_OFFSET_ADDRESS_CONTROL_NOW		0x1010
+#define REG_OFFSET_MEMORY_TYPE_NOW		0x1128
+#define REG_OFFSET_SCRUB_CONTROL0_NOW		0x1170
+#define REG_OFFSET_FORMAT_CONTROL	0x18
+
+/* DMC-520 types, masks and bitfields */
+#define DRAM_ECC_INT_CE_BIT			BIT(2)
+#define DRAM_ECC_INT_UE_BIT			BIT(3)
+#define ALL_INT_MASK				GENMASK(9, 0)
+#define MEMORY_WIDTH_MASK			GENMASK(1, 0)
+#define SCRUB_TRIGGER0_NEXT_MASK		GENMASK(1, 0)
+#define REG_FIELD_DRAM_ECC_ENABLED		GENMASK(1, 0)
+#define REG_FIELD_MEMORY_TYPE			GENMASK(2, 0)
+#define REG_FIELD_DEVICE_WIDTH			GENMASK(9, 8)
+#define REG_FIELD_ADDRESS_CONTROL_COL		GENMASK(2, 0)
+#define REG_FIELD_ADDRESS_CONTROL_ROW		GENMASK(10, 8)
+#define REG_FIELD_ADDRESS_CONTROL_BANK		GENMASK(18, 16)
+#define REG_FIELD_ADDRESS_CONTROL_RANK		GENMASK(25, 24)
+#define REG_FIELD_ERR_INFO_LOW_VALID		BIT(0)
+#define REG_FIELD_ERR_INFO_LOW_COL		GENMASK(10, 1)
+#define REG_FIELD_ERR_INFO_LOW_ROW		GENMASK(28, 11)
+#define REG_FIELD_ERR_INFO_LOW_RANK		GENMASK(31, 29)
+#define REG_FIELD_ERR_INFO_HIGH_BANK		GENMASK(3, 0)
+#define REG_FIELD_ERR_INFO_HIGH_VALID		BIT(31)
+
+#define DRAM_ADDRESS_CONTROL_MIN_COL_BITS	8
+#define DRAM_ADDRESS_CONTROL_MIN_ROW_BITS	11
+
+#define DMC520_SCRUB_TRIGGER_ERR_DETECT		2
+#define DMC520_SCRUB_TRIGGER_IDLE			3
+
+/* Driver settings */
+/* The max-length message would be: "rank:7 bank:15 row:262143 col:1023".
+ * Max length is 34. Using a 40-size buffer is enough.
+ */
+#define EDAC_MSG_BUF_SIZE			40
+#define EDAC_MOD_NAME				"dmc520-edac"
+#define EDAC_CTL_NAME				"dmc520"
+
+/* the data bus width for the attached memory chips. */
+enum dmc520_mem_width {
+	MEM_WIDTH_X32 = 2,
+	MEM_WIDTH_X64 = 3
+};
+
+/* memory type */
+enum dmc520_mem_type {
+	MEM_TYPE_DDR3 = 1,
+	MEM_TYPE_DDR4 = 2
+};
+
+/* memory device width */
+enum dmc520_dev_width {
+	DEV_WIDTH_X4 = 0,
+	DEV_WIDTH_X8 = 1,
+	DEV_WIDTH_X16 = 2
+};
+
+struct ecc_error_info {
+	u32 col;
+	u32 row;
+	u32 bank;
+	u32 rank;
+};
+
+/* The EDAC driver private data */
+struct dmc520_edac {
+	void __iomem *reg_base;
+	u32 nintr;
+	u32 interrupt_mask_all;
+	spinlock_t ecc_lock;
+	u32 interrupt_masks[0];
+};
+
+static int dmc520_mc_idx;
+
+static irqreturn_t
+dmc520_edac_dram_all_isr(int irq, struct mem_ctl_info *mci, u32 interrupt_mask);
+
+#define DECLARE_ISR(index) \
+static irqreturn_t dmc520_isr_##index (int irq, void *data) \
+{ \
+	struct mem_ctl_info *mci; \
+	struct dmc520_edac *edac; \
+	mci = data; \
+	edac = mci->pvt_info; \
+	return dmc520_edac_dram_all_isr(irq, mci, edac->interrupt_masks[index]); \
+}
+
+DECLARE_ISR(0)
+DECLARE_ISR(1)
+/* More DECLARE_ISR(index) can be added to support more interrupt lines. */
+
+irq_handler_t dmc520_isr_array[] = {
+	dmc520_isr_0,
+	dmc520_isr_1
+	/* More dmc520_isr_index can be added to support more interrupt lines. */
+};
+
+static u32 dmc520_read_reg(struct dmc520_edac *edac, u32 offset)
+{
+	return readl(edac->reg_base + offset);
+}
+
+static void dmc520_write_reg(struct dmc520_edac *edac, u32 val, u32 offset)
+{
+	writel(val, edac->reg_base + offset);
+}
+
+static u32 dmc520_calc_dram_ecc_error(u32 value)
+{
+	u32 total = 0;
+
+	/* Each rank's error counter takes one byte */
+	while (value > 0) {
+		total += (value & 0xFF);
+		value >>= 8;
+	}
+	return total;
+}
+
+static u32 dmc520_get_dram_ecc_error_count(struct dmc520_edac *edac,
+					   bool is_ce)
+{
+	u32 reg_offset_low, reg_offset_high;
+	u32 err_low, err_high;
+	u32 err_count;
+
+	reg_offset_low = is_ce ? REG_OFFSET_ECC_ERRC_COUNT_31_00 :
+				 REG_OFFSET_ECC_ERRD_COUNT_31_00;
+	reg_offset_high = is_ce ? REG_OFFSET_ECC_ERRC_COUNT_63_32 :
+				  REG_OFFSET_ECC_ERRD_COUNT_63_32;
+
+	err_low = dmc520_read_reg(edac, reg_offset_low);
+	err_high = dmc520_read_reg(edac, reg_offset_high);
+	/* Reset error counters */
+	dmc520_write_reg(edac, 0, reg_offset_low);
+	dmc520_write_reg(edac, 0, reg_offset_high);
+
+	err_count = dmc520_calc_dram_ecc_error(err_low) +
+		   dmc520_calc_dram_ecc_error(err_high);
+
+	return err_count;
+}
+
+static void dmc520_get_dram_ecc_error_info(struct dmc520_edac *edac,
+					   bool is_ce,
+					   struct ecc_error_info *info)
+{
+	u32 reg_offset_low, reg_offset_high;
+	u32 reg_val_low, reg_val_high;
+	bool valid;
+
+	reg_offset_low = is_ce ? REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_31_00 :
+				 REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_31_00;
+	reg_offset_high = is_ce ? REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_63_32 :
+				  REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_63_32;
+
+	reg_val_low = dmc520_read_reg(edac, reg_offset_low);
+	reg_val_high = dmc520_read_reg(edac, reg_offset_high);
+
+	valid = (FIELD_GET(REG_FIELD_ERR_INFO_LOW_VALID, reg_val_low) != 0) &&
+		(FIELD_GET(REG_FIELD_ERR_INFO_HIGH_VALID, reg_val_high) != 0);
+
+	if (valid) {
+		info->col = FIELD_GET(REG_FIELD_ERR_INFO_LOW_COL, reg_val_low);
+		info->row = FIELD_GET(REG_FIELD_ERR_INFO_LOW_ROW, reg_val_low);
+		info->rank = FIELD_GET(REG_FIELD_ERR_INFO_LOW_RANK, reg_val_low);
+		info->bank = FIELD_GET(REG_FIELD_ERR_INFO_HIGH_BANK, reg_val_high);
+	} else {
+		memset(info, 0, sizeof(struct ecc_error_info));
+	}
+}
+
+static bool dmc520_is_ecc_enabled(void __iomem *reg_base)
+{
+	u32 reg_val = readl(reg_base + REG_OFFSET_FEATURE_CONFIG);
+
+	return (FIELD_GET(REG_FIELD_DRAM_ECC_ENABLED, reg_val) != 0);
+}
+
+static enum scrub_type dmc520_get_scrub_type(struct dmc520_edac *edac)
+{
+	enum scrub_type type = SCRUB_NONE;
+	u32 reg_val, scrub_cfg;
+
+	reg_val = dmc520_read_reg(edac, REG_OFFSET_SCRUB_CONTROL0_NOW);
+	scrub_cfg = FIELD_GET(SCRUB_TRIGGER0_NEXT_MASK, reg_val);
+
+	if (DMC520_SCRUB_TRIGGER_ERR_DETECT == scrub_cfg ||
+		DMC520_SCRUB_TRIGGER_IDLE == scrub_cfg)
+		type = SCRUB_HW_PROG;
+
+	return type;
+}
+
+/* Get the memory data bus width, in number of bytes. */
+static u32 dmc520_get_memory_width(struct dmc520_edac *edac)
+{
+	static u32 mem_width;
+	u32 reg_val;
+	enum dmc520_mem_width mem_width_field;
+
+	if (mem_width == 0) {
+		reg_val = dmc520_read_reg(edac, REG_OFFSET_FORMAT_CONTROL);
+		mem_width_field = FIELD_GET(MEMORY_WIDTH_MASK, reg_val);
+
+		if (mem_width_field == MEM_WIDTH_X32)
+			mem_width = 4; /* 32-bits, 4 bytes */
+		else if (mem_width_field == MEM_WIDTH_X64)
+			mem_width = 8; /* 64-bits, 8 bytes */
+	}
+
+	return mem_width;
+}
+
+static enum mem_type dmc520_get_mtype(struct dmc520_edac *edac)
+{
+	enum mem_type mt = MEM_UNKNOWN;
+	u32 reg_val;
+	enum dmc520_mem_type type;
+
+	reg_val = dmc520_read_reg(edac, REG_OFFSET_MEMORY_TYPE_NOW);
+	type = FIELD_GET(REG_FIELD_MEMORY_TYPE, reg_val);
+
+	switch (type) {
+	case MEM_TYPE_DDR3:
+		mt = MEM_DDR3;
+		break;
+
+	case MEM_TYPE_DDR4:
+		mt = MEM_DDR4;
+		break;
+	}
+
+	return mt;
+}
+
+static enum dev_type dmc520_get_dtype(struct dmc520_edac *edac)
+{
+	enum dev_type dt = DEV_UNKNOWN;
+	u32 reg_val;
+	enum dmc520_dev_width device_width;
+
+	reg_val = dmc520_read_reg(edac, REG_OFFSET_MEMORY_TYPE_NOW);
+	device_width = FIELD_GET(REG_FIELD_DEVICE_WIDTH, reg_val);
+
+	switch (device_width) {
+	case DEV_WIDTH_X4:
+		dt = DEV_X4;
+		break;
+
+	case DEV_WIDTH_X8:
+		dt = DEV_X8;
+		break;
+
+	case DEV_WIDTH_X16:
+		dt = DEV_X16;
+		break;
+	}
+
+	return dt;
+}
+
+static u32 dmc520_get_rank_count(void __iomem *reg_base)
+{
+	u32 reg_val, rank_bits;
+
+	reg_val = readl(reg_base + REG_OFFSET_ADDRESS_CONTROL_NOW);
+	rank_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_RANK, reg_val);
+
+	return (1 << rank_bits);
+}
+
+static u64 dmc520_get_rank_size(struct dmc520_edac *edac)
+{
+	u32 reg_val, col_bits, row_bits, bank_bits;
+
+	reg_val = dmc520_read_reg(edac, REG_OFFSET_ADDRESS_CONTROL_NOW);
+
+	col_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_COL, reg_val) +
+		   DRAM_ADDRESS_CONTROL_MIN_COL_BITS;
+	row_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_ROW, reg_val) +
+		   DRAM_ADDRESS_CONTROL_MIN_ROW_BITS;
+	bank_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_BANK, reg_val);
+
+	return (u64)dmc520_get_memory_width(edac) << (col_bits + row_bits + bank_bits);
+}
+
+static void dmc520_handle_dram_ecc_errors(struct mem_ctl_info *mci,
+					  bool is_ce)
+{
+	struct ecc_error_info info;
+	struct dmc520_edac *edac;
+	u32 cnt;
+	char message[EDAC_MSG_BUF_SIZE];
+
+	edac = mci->pvt_info;
+	dmc520_get_dram_ecc_error_info(edac, is_ce, &info);
+
+	cnt = dmc520_get_dram_ecc_error_count(edac, is_ce);
+
+	if (cnt > 0) {
+		snprintf(message, ARRAY_SIZE(message),
+			 "rank:%d bank:%d row:%d col:%d",
+			 info.rank, info.bank,
+			 info.row, info.col);
+
+		spin_lock(&edac->ecc_lock);
+		edac_mc_handle_error((is_ce ? HW_EVENT_ERR_CORRECTED :
+				     HW_EVENT_ERR_UNCORRECTED),
+				     mci, cnt, 0, 0, 0, info.rank, -1, -1,
+				     message, "");
+		spin_unlock(&edac->ecc_lock);
+	}
+}
+
+static irqreturn_t dmc520_edac_dram_ecc_isr(int irq, struct mem_ctl_info *mci, bool is_ce)
+{
+	u32 i_mask;
+	struct dmc520_edac *edac;
+
+	edac = mci->pvt_info;
+
+	i_mask = is_ce ? DRAM_ECC_INT_CE_BIT : DRAM_ECC_INT_UE_BIT;
+
+	dmc520_handle_dram_ecc_errors(mci, is_ce);
+
+	dmc520_write_reg(edac, i_mask, REG_OFFSET_INTERRUPT_CLR);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t
+dmc520_edac_dram_all_isr(int irq, struct mem_ctl_info *mci, u32 interrupt_mask)
+{
+	struct dmc520_edac *edac;
+	u32 status;
+	irqreturn_t irq_ret = IRQ_NONE;
+
+	edac = mci->pvt_info;
+
+	status = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_STATUS);
+
+	if ((interrupt_mask & DRAM_ECC_INT_CE_BIT) &&
+		(status & DRAM_ECC_INT_CE_BIT))
+		irq_ret = dmc520_edac_dram_ecc_isr(irq, mci, true);
+
+	if ((interrupt_mask & DRAM_ECC_INT_UE_BIT) &&
+		(status & DRAM_ECC_INT_UE_BIT))
+		irq_ret = dmc520_edac_dram_ecc_isr(irq, mci, false);
+
+	/* If in the future there are more supported interrupts in a different
+	 * platform, more condition statements can be added here for each
+	 * interrupt flag, together with its corresponding isr implementations.
+	 */
+
+	return irq_ret;
+}
+
+static void dmc520_init_csrow(struct mem_ctl_info *mci)
+{
+	struct csrow_info *csi;
+	struct dimm_info *dimm;
+	int row, ch;
+	enum dev_type dt;
+	enum mem_type mt;
+	u64 rs;
+	u32 pages_per_rank;
+	struct dmc520_edac *edac = mci->pvt_info;
+
+	dt = dmc520_get_dtype(edac);
+	mt = dmc520_get_mtype(edac);
+	rs = dmc520_get_rank_size(edac);
+	pages_per_rank = rs >> PAGE_SHIFT;
+
+	for (row = 0; row < mci->nr_csrows; row++) {
+		csi = mci->csrows[row];
+
+		for (ch = 0; ch < csi->nr_channels; ch++) {
+			dimm		= csi->channels[ch]->dimm;
+			dimm->grain	= dmc520_get_memory_width(edac);
+			dimm->dtype	= dt;
+			dimm->mtype	= mt;
+			dimm->edac_mode	= EDAC_FLAG_SECDED;
+			dimm->nr_pages	= pages_per_rank / csi->nr_channels;
+		}
+	}
+}
+
+static int dmc520_edac_probe(struct platform_device *pdev)
+{
+	struct device *dev;
+	struct dmc520_edac *edac;
+	struct mem_ctl_info *mci;
+	struct edac_mc_layer layers[1];
+	int ret, intr_index, nintr, nintr_registered = 0;
+	struct resource *res;
+	void __iomem *reg_base;
+	u32 reg_val;
+
+	/* Parsing the device node */
+	dev = &pdev->dev;
+
+	nintr = of_property_count_u32_elems(dev->of_node, "interrupt-config");
+	if (nintr <= 0) {
+		edac_printk(KERN_ERR, EDAC_MOD_NAME,
+			"Invalid device node configuration: at least one interrupt "
+			"line & config is expected.\n");
+		return -EINVAL;
+	}
+
+	if (nintr > ARRAY_SIZE(dmc520_isr_array)) {
+		edac_printk(KERN_ERR, EDAC_MOD_NAME,
+			"Invalid device node configuration: # of interrupt config "
+			"elements (%d) can not exceed %ld.\n",
+			nintr, ARRAY_SIZE(dmc520_isr_array));
+		return -EINVAL;
+	}
+
+	/* Initialize dmc520 edac */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	reg_base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(reg_base))
+		return PTR_ERR(reg_base);
+
+	if (!dmc520_is_ecc_enabled(reg_base))
+		return -ENXIO;
+
+	layers[0].type = EDAC_MC_LAYER_CHIP_SELECT;
+	layers[0].size = dmc520_get_rank_count(reg_base);
+	layers[0].is_virt_csrow = true;
+
+	mci = edac_mc_alloc(dmc520_mc_idx++, ARRAY_SIZE(layers), layers,
+			    sizeof(struct dmc520_edac) + sizeof(u32) * nintr);
+	if (!mci) {
+		edac_printk(KERN_ERR, EDAC_MOD_NAME,
+			    "Failed to allocate memory for mc instance\n");
+		return -ENOMEM;
+	}
+
+	edac = mci->pvt_info;
+	edac->reg_base = reg_base;
+	edac->nintr = nintr;
+	edac->interrupt_mask_all = 0;
+	spin_lock_init(&edac->ecc_lock);
+
+	ret = of_property_read_u32_array(dev->of_node, "interrupt-config",
+			edac->interrupt_masks, nintr);
+	if (ret) {
+		edac_printk(KERN_ERR, EDAC_MOD_NAME,
+			"Failed to get interrupt-config arrays.\n");
+		goto err_free_mc;
+	}
+
+	for (intr_index = 0; intr_index < nintr; ++intr_index) {
+		if (edac->interrupt_mask_all & edac->interrupt_masks[intr_index]) {
+			edac_printk(KERN_ERR, EDAC_MC,
+				"interrupt-config error: "
+				"element %d's interrupt mask %d has overlap.\n",
+				intr_index, edac->interrupt_masks[intr_index]);
+			goto err_free_mc;
+		}
+
+		edac->interrupt_mask_all |= edac->interrupt_masks[intr_index];
+	}
+
+	if ((edac->interrupt_mask_all | ALL_INT_MASK) != ALL_INT_MASK) {
+		edac_printk(KERN_WARNING, EDAC_MOD_NAME,
+			"interrupt-config warning: "
+			"interrupt mask (0x%x) is not supported by dmc520 (0x%lx).\n",
+			edac->interrupt_mask_all, ALL_INT_MASK);
+	}
+	edac->interrupt_mask_all &= ALL_INT_MASK;
+
+	platform_set_drvdata(pdev, mci);
+
+	mci->pdev = dev;
+	mci->mtype_cap = MEM_FLAG_DDR3 | MEM_FLAG_DDR4;
+	mci->edac_ctl_cap = EDAC_FLAG_NONE | EDAC_FLAG_SECDED;
+	mci->edac_cap = EDAC_FLAG_SECDED;
+	mci->scrub_cap = SCRUB_FLAG_HW_SRC;
+	mci->scrub_mode = dmc520_get_scrub_type(edac);
+	mci->ctl_name = EDAC_CTL_NAME;
+	mci->dev_name = dev_name(mci->pdev);
+	mci->mod_name = EDAC_MOD_NAME;
+	mci->ctl_page_to_phys = NULL;
+
+	edac_op_state = EDAC_OPSTATE_INT;
+
+	dmc520_init_csrow(mci);
+
+	ret = edac_mc_add_mc(mci);
+	if (ret) {
+		edac_printk(KERN_ERR, EDAC_MOD_NAME,
+			"Failed to register with EDAC core\n");
+		goto err_free_mc;
+	}
+
+	/* Clear interrupts, not affecting other unrelated interrupts */
+	reg_val = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_CONTROL);
+	dmc520_write_reg(edac, reg_val & (~(edac->interrupt_mask_all)),
+			REG_OFFSET_INTERRUPT_CONTROL);
+	dmc520_write_reg(edac, edac->interrupt_mask_all,
+			REG_OFFSET_INTERRUPT_CLR);
+
+	for (intr_index = 0; intr_index < nintr; ++intr_index) {
+		int irq_id = platform_get_irq(pdev, intr_index);
+
+		if (irq_id < 0) {
+			edac_printk(KERN_ERR, EDAC_MC,
+				    "Failed to get irq #%d\n", intr_index);
+			ret = -ENODEV;
+			goto err_free_irq;
+		}
+
+		ret = devm_request_irq(&pdev->dev, irq_id,
+				dmc520_isr_array[intr_index], IRQF_SHARED,
+				dev_name(&pdev->dev), mci);
+		if (ret < 0) {
+			edac_printk(KERN_ERR, EDAC_MC,
+				    "Failed to request irq %d\n", irq_id);
+			goto err_free_irq;
+		}
+
+		++nintr_registered;
+	}
+
+	/* Reset DRAM CE/UE counters */
+	if (edac->interrupt_mask_all & DRAM_ECC_INT_CE_BIT)
+		dmc520_get_dram_ecc_error_count(edac, true);
+
+	if (edac->interrupt_mask_all & DRAM_ECC_INT_UE_BIT)
+		dmc520_get_dram_ecc_error_count(edac, false);
+
+	/* Enable interrupts, not affecting other unrelated interrupts */
+	dmc520_write_reg(edac,
+		reg_val | edac->interrupt_mask_all,
+		REG_OFFSET_INTERRUPT_CONTROL);
+
+	return 0;
+
+err_free_irq:
+	for (intr_index = 0; intr_index < nintr_registered; ++intr_index) {
+		int irq_id = platform_get_irq(pdev, intr_index);
+
+		devm_free_irq(&pdev->dev, irq_id, mci);
+	}
+	edac_mc_del_mc(&pdev->dev);
+err_free_mc:
+	edac_mc_free(mci);
+
+	return ret;
+}
+
+static int dmc520_edac_remove(struct platform_device *pdev)
+{
+	struct dmc520_edac *edac;
+	struct mem_ctl_info *mci;
+	u32 reg_val, intr_index;
+
+	mci = platform_get_drvdata(pdev);
+	edac = mci->pvt_info;
+
+	/* Disable interrupts */
+	reg_val = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_CONTROL);
+	dmc520_write_reg(edac, reg_val & (~(edac->interrupt_mask_all)),
+			REG_OFFSET_INTERRUPT_CONTROL);
+
+	/* free irq's */
+	for (intr_index = 0; intr_index < edac->nintr; ++intr_index) {
+		int irq_id = platform_get_irq(pdev, intr_index);
+
+		devm_free_irq(&pdev->dev, irq_id, mci);
+	}
+
+	edac_mc_del_mc(&pdev->dev);
+	edac_mc_free(mci);
+
+	return 0;
+}
+
+static const struct of_device_id dmc520_edac_driver_id[] = {
+	{ .compatible = "arm,dmc-520", },
+	{ /* end of table */ }
+};
+
+MODULE_DEVICE_TABLE(of, dmc520_edac_driver_id);
+
+static struct platform_driver dmc520_edac_driver = {
+	.driver = {
+		.name = "dmc520",
+		.of_match_table = dmc520_edac_driver_id,
+	},
+
+	.probe = dmc520_edac_probe,
+	.remove = dmc520_edac_remove
+};
+
+module_platform_driver(dmc520_edac_driver);
+
+MODULE_AUTHOR(
+	"Rui Zhao <ruizhao@microsoft.com>, Lei Wang <lewan@microsoft.com>");
+MODULE_DESCRIPTION("DMC-520 ECC driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1

Re: [PATCH v5 2/2] EDAC: add EDAC driver for DMC520

[Borislav Petkov]

On Thu, Jul 25, 2019 at 12:49:27AM +0000, Lei Wang wrote:
> New driver supports error detection and correction on the devices with ARM
> DMC-520 memory controller.
> 
> Signed-off-by: Lei Wang <leiwang_git@outlook.com>
> Reviewed-by: James Morse <james.morse@arm.com>
> ---
>     Changes in v5:
>         - When enable configured interrupts, do not potentially disable
>           other irrelevant interrupts.
>         - fix return type of dmc520_get_scrub_type to enum scrub_type
>         - Use capital letters for enum
>         - Retrieve memory width from dmc register format_control
>         - use cheaper spin_lock API.
>         - Remove compatible line for "brcm,dmc-520"
>         - Add James' Reviewed-by
> ---
>  MAINTAINERS                |   6 +
>  drivers/edac/Kconfig       |   7 +
>  drivers/edac/Makefile      |   1 +
>  drivers/edac/dmc520_edac.c | 632 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 646 insertions(+)
>  create mode 100644 drivers/edac/dmc520_edac.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 77eae44bf5de..7c1ac8bc8ea1 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5703,6 +5703,12 @@ F:	Documentation/driver-api/edac.rst
>  F:	drivers/edac/
>  F:	include/linux/edac.h
>  
> +EDAC-DMC520
> +M:	Lei Wang <lewan@microsoft.com>
> +L:	linux-edac@vger.kernel.org
> +S:	Supported
> +F:	drivers/edac/dmc520_edac.c
> +
>  EDAC-E752X
>  M:	Mark Gross <mark.gross@intel.com>
>  L:	linux-edac@vger.kernel.org
> diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
> index 200c04ce5b0e..7fde5aea0c1a 100644
> --- a/drivers/edac/Kconfig
> +++ b/drivers/edac/Kconfig
> @@ -510,4 +510,11 @@ config EDAC_ASPEED
>  	  First, ECC must be configured in the bootloader. Then, this driver
>  	  will expose error counters via the EDAC kernel framework.
>  
> +config EDAC_DMC520
> +       tristate "ARM DMC-520 ECC"
> +       depends on ARM64
> +       help
> +         Support for error detection and correction on the
> +         SoCs with ARM DMC-520 DRAM controller.
> +
>  endif # EDAC
> diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
> index 165ca65e1a3a..e0d98f5b2045 100644
> --- a/drivers/edac/Makefile
> +++ b/drivers/edac/Makefile
> @@ -85,3 +85,4 @@ obj-$(CONFIG_EDAC_XGENE)		+= xgene_edac.o
>  obj-$(CONFIG_EDAC_TI)			+= ti_edac.o
>  obj-$(CONFIG_EDAC_QCOM)			+= qcom_edac.o
>  obj-$(CONFIG_EDAC_ASPEED)		+= aspeed_edac.o
> +obj-$(CONFIG_EDAC_DMC520)		+= dmc520_edac.o
> diff --git a/drivers/edac/dmc520_edac.c b/drivers/edac/dmc520_edac.c
> new file mode 100644
> index 000000000000..aeb8d84405cf
> --- /dev/null
> +++ b/drivers/edac/dmc520_edac.c
> @@ -0,0 +1,632 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* EDAC driver for DMC-520 */

That comment is kinda useless.

> +#include <linux/bitfield.h>
> +#include <linux/edac.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/spinlock.h>
> +#include "edac_mc.h"
> +
> +/* DMC-520 registers */
> +#define REG_OFFSET_FEATURE_CONFIG		0x130
> +#define REG_OFFSET_ECC_ERRC_COUNT_31_00		0x158
> +#define REG_OFFSET_ECC_ERRC_COUNT_63_32		0x15C
> +#define REG_OFFSET_ECC_ERRD_COUNT_31_00		0x160
> +#define REG_OFFSET_ECC_ERRD_COUNT_63_32		0x164
> +#define REG_OFFSET_INTERRUPT_CONTROL		0x500
> +#define REG_OFFSET_INTERRUPT_CLR		0x508
> +#define REG_OFFSET_INTERRUPT_STATUS		0x510
> +#define REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_31_00	0x528
> +#define REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_63_32	0x52C
> +#define REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_31_00	0x530
> +#define REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_63_32	0x534
> +#define REG_OFFSET_ADDRESS_CONTROL_NOW		0x1010
> +#define REG_OFFSET_MEMORY_TYPE_NOW		0x1128
> +#define REG_OFFSET_SCRUB_CONTROL0_NOW		0x1170
> +#define REG_OFFSET_FORMAT_CONTROL	0x18
> +
> +/* DMC-520 types, masks and bitfields */
> +#define DRAM_ECC_INT_CE_BIT			BIT(2)
> +#define DRAM_ECC_INT_UE_BIT			BIT(3)
> +#define ALL_INT_MASK				GENMASK(9, 0)
> +#define MEMORY_WIDTH_MASK			GENMASK(1, 0)
> +#define SCRUB_TRIGGER0_NEXT_MASK		GENMASK(1, 0)
> +#define REG_FIELD_DRAM_ECC_ENABLED		GENMASK(1, 0)
> +#define REG_FIELD_MEMORY_TYPE			GENMASK(2, 0)
> +#define REG_FIELD_DEVICE_WIDTH			GENMASK(9, 8)
> +#define REG_FIELD_ADDRESS_CONTROL_COL		GENMASK(2, 0)
> +#define REG_FIELD_ADDRESS_CONTROL_ROW		GENMASK(10, 8)
> +#define REG_FIELD_ADDRESS_CONTROL_BANK		GENMASK(18, 16)
> +#define REG_FIELD_ADDRESS_CONTROL_RANK		GENMASK(25, 24)
> +#define REG_FIELD_ERR_INFO_LOW_VALID		BIT(0)
> +#define REG_FIELD_ERR_INFO_LOW_COL		GENMASK(10, 1)
> +#define REG_FIELD_ERR_INFO_LOW_ROW		GENMASK(28, 11)
> +#define REG_FIELD_ERR_INFO_LOW_RANK		GENMASK(31, 29)
> +#define REG_FIELD_ERR_INFO_HIGH_BANK		GENMASK(3, 0)
> +#define REG_FIELD_ERR_INFO_HIGH_VALID		BIT(31)
> +
> +#define DRAM_ADDRESS_CONTROL_MIN_COL_BITS	8
> +#define DRAM_ADDRESS_CONTROL_MIN_ROW_BITS	11
> +
> +#define DMC520_SCRUB_TRIGGER_ERR_DETECT		2
> +#define DMC520_SCRUB_TRIGGER_IDLE			3

One tab too many. Keep them all vertically aligned.

> +
> +/* Driver settings */
> +/* The max-length message would be: "rank:7 bank:15 row:262143 col:1023".
> + * Max length is 34. Using a 40-size buffer is enough.
> + */
> +#define EDAC_MSG_BUF_SIZE			40

That define is driver-local only. Prefix it with "DMC520_" or so, not
with "EDAC_".

> +#define EDAC_MOD_NAME				"dmc520-edac"
> +#define EDAC_CTL_NAME				"dmc520"
> +
> +/* the data bus width for the attached memory chips. */
> +enum dmc520_mem_width {
> +	MEM_WIDTH_X32 = 2,
> +	MEM_WIDTH_X64 = 3
> +};
> +
> +/* memory type */
> +enum dmc520_mem_type {
> +	MEM_TYPE_DDR3 = 1,
> +	MEM_TYPE_DDR4 = 2
> +};
> +
> +/* memory device width */
> +enum dmc520_dev_width {
> +	DEV_WIDTH_X4 = 0,
> +	DEV_WIDTH_X8 = 1,
> +	DEV_WIDTH_X16 = 2
> +};
> +
> +struct ecc_error_info {
> +	u32 col;
> +	u32 row;
> +	u32 bank;
> +	u32 rank;
> +};
> +
> +/* The EDAC driver private data */
> +struct dmc520_edac {
> +	void __iomem *reg_base;
> +	u32 nintr;
> +	u32 interrupt_mask_all;
> +	spinlock_t ecc_lock;
> +	u32 interrupt_masks[0];
> +};
> +
> +static int dmc520_mc_idx;
> +
> +static irqreturn_t
> +dmc520_edac_dram_all_isr(int irq, struct mem_ctl_info *mci, u32 interrupt_mask);
> +
> +#define DECLARE_ISR(index) \
> +static irqreturn_t dmc520_isr_##index (int irq, void *data) \

Please integrate scripts/checkpatch.pl into your patch creation
workflow. Some of the warnings/errors *actually* make sense.

WARNING: space prohibited between function name and open parenthesis '('
#200: FILE: drivers/edac/dmc520_edac.c:108:
+static irqreturn_t dmc520_isr_##index (int irq, void *data) \


> +{ \
> +	struct mem_ctl_info *mci; \
> +	struct dmc520_edac *edac; \
> +	mci = data; \
> +	edac = mci->pvt_info; \
> +	return dmc520_edac_dram_all_isr(irq, mci, edac->interrupt_masks[index]); \
> +}
> +
> +DECLARE_ISR(0)
> +DECLARE_ISR(1)
> +/* More DECLARE_ISR(index) can be added to support more interrupt lines. */
> +
> +irq_handler_t dmc520_isr_array[] = {
> +	dmc520_isr_0,
> +	dmc520_isr_1
> +	/* More dmc520_isr_index can be added to support more interrupt lines. */

What are those comments really for?

> +};
> +
> +static u32 dmc520_read_reg(struct dmc520_edac *edac, u32 offset)
> +{
> +	return readl(edac->reg_base + offset);
> +}
> +
> +static void dmc520_write_reg(struct dmc520_edac *edac, u32 val, u32 offset)
> +{
> +	writel(val, edac->reg_base + offset);
> +}
> +
> +static u32 dmc520_calc_dram_ecc_error(u32 value)
> +{
> +	u32 total = 0;
> +
> +	/* Each rank's error counter takes one byte */
> +	while (value > 0) {
> +		total += (value & 0xFF);
> +		value >>= 8;
> +	}
> +	return total;
> +}
> +
> +static u32 dmc520_get_dram_ecc_error_count(struct dmc520_edac *edac,
> +					   bool is_ce)
> +{
> +	u32 reg_offset_low, reg_offset_high;
> +	u32 err_low, err_high;
> +	u32 err_count;
> +
> +	reg_offset_low = is_ce ? REG_OFFSET_ECC_ERRC_COUNT_31_00 :
> +				 REG_OFFSET_ECC_ERRD_COUNT_31_00;
> +	reg_offset_high = is_ce ? REG_OFFSET_ECC_ERRC_COUNT_63_32 :
> +				  REG_OFFSET_ECC_ERRD_COUNT_63_32;
> +
> +	err_low = dmc520_read_reg(edac, reg_offset_low);
> +	err_high = dmc520_read_reg(edac, reg_offset_high);
> +	/* Reset error counters */
> +	dmc520_write_reg(edac, 0, reg_offset_low);
> +	dmc520_write_reg(edac, 0, reg_offset_high);
> +
> +	err_count = dmc520_calc_dram_ecc_error(err_low) +
> +		   dmc520_calc_dram_ecc_error(err_high);
> +
> +	return err_count;
> +}
> +
> +static void dmc520_get_dram_ecc_error_info(struct dmc520_edac *edac,
> +					   bool is_ce,
> +					   struct ecc_error_info *info)
> +{
> +	u32 reg_offset_low, reg_offset_high;
> +	u32 reg_val_low, reg_val_high;
> +	bool valid;
> +
> +	reg_offset_low = is_ce ? REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_31_00 :
> +				 REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_31_00;
> +	reg_offset_high = is_ce ? REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_63_32 :
> +				  REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_63_32;
> +
> +	reg_val_low = dmc520_read_reg(edac, reg_offset_low);
> +	reg_val_high = dmc520_read_reg(edac, reg_offset_high);
> +
> +	valid = (FIELD_GET(REG_FIELD_ERR_INFO_LOW_VALID, reg_val_low) != 0) &&
> +		(FIELD_GET(REG_FIELD_ERR_INFO_HIGH_VALID, reg_val_high) != 0);
> +
> +	if (valid) {
> +		info->col = FIELD_GET(REG_FIELD_ERR_INFO_LOW_COL, reg_val_low);
> +		info->row = FIELD_GET(REG_FIELD_ERR_INFO_LOW_ROW, reg_val_low);
> +		info->rank = FIELD_GET(REG_FIELD_ERR_INFO_LOW_RANK, reg_val_low);
> +		info->bank = FIELD_GET(REG_FIELD_ERR_INFO_HIGH_BANK, reg_val_high);
> +	} else {
> +		memset(info, 0, sizeof(struct ecc_error_info));
> +	}
> +}
> +
> +static bool dmc520_is_ecc_enabled(void __iomem *reg_base)
> +{
> +	u32 reg_val = readl(reg_base + REG_OFFSET_FEATURE_CONFIG);
> +
> +	return (FIELD_GET(REG_FIELD_DRAM_ECC_ENABLED, reg_val) != 0);

No need for that " != 0" at the end.

> +}
> +
> +static enum scrub_type dmc520_get_scrub_type(struct dmc520_edac *edac)
> +{
> +	enum scrub_type type = SCRUB_NONE;
> +	u32 reg_val, scrub_cfg;
> +
> +	reg_val = dmc520_read_reg(edac, REG_OFFSET_SCRUB_CONTROL0_NOW);
> +	scrub_cfg = FIELD_GET(SCRUB_TRIGGER0_NEXT_MASK, reg_val);
> +
> +	if (DMC520_SCRUB_TRIGGER_ERR_DETECT == scrub_cfg ||
> +		DMC520_SCRUB_TRIGGER_IDLE == scrub_cfg)
> +		type = SCRUB_HW_PROG;

More from checkpatch:

WARNING: Comparisons should place the constant on the right side of the test
#309: FILE: drivers/edac/dmc520_edac.c:217:
+       if (DMC520_SCRUB_TRIGGER_ERR_DETECT == scrub_cfg ||

WARNING: Comparisons should place the constant on the right side of the test
#310: FILE: drivers/edac/dmc520_edac.c:218:
+               DMC520_SCRUB_TRIGGER_IDLE == scrub_cfg)


> +
> +	return type;
> +}
> +
> +/* Get the memory data bus width, in number of bytes. */
> +static u32 dmc520_get_memory_width(struct dmc520_edac *edac)
> +{
> +	static u32 mem_width;
> +	u32 reg_val;
> +	enum dmc520_mem_width mem_width_field;

Please sort function local variables declaration in a reverse christmas
tree order:

	<type A> longest_variable_name;
	<type B> shorter_var_name;
	<type C> even_shorter;
	<type D> i;

Here and in the other functions.

> +
> +	if (mem_width == 0) {

Flip that check and save yourself an indentation level:

	if (mem_width)
		return;

	reg_val = ...



> +		reg_val = dmc520_read_reg(edac, REG_OFFSET_FORMAT_CONTROL);
> +		mem_width_field = FIELD_GET(MEMORY_WIDTH_MASK, reg_val);
> +
> +		if (mem_width_field == MEM_WIDTH_X32)
> +			mem_width = 4; /* 32-bits, 4 bytes */
> +		else if (mem_width_field == MEM_WIDTH_X64)
> +			mem_width = 8; /* 64-bits, 8 bytes */

Please no side-comments. And those you can directly remove as they're
useless - your defines and variables should be named properly so that
there is no need for a comment here additionally.

> +	}
> +
> +	return mem_width;
> +}
> +
> +static enum mem_type dmc520_get_mtype(struct dmc520_edac *edac)
> +{
> +	enum mem_type mt = MEM_UNKNOWN;
> +	u32 reg_val;
> +	enum dmc520_mem_type type;
> +
> +	reg_val = dmc520_read_reg(edac, REG_OFFSET_MEMORY_TYPE_NOW);
> +	type = FIELD_GET(REG_FIELD_MEMORY_TYPE, reg_val);
> +
> +	switch (type) {
> +	case MEM_TYPE_DDR3:
> +		mt = MEM_DDR3;
> +		break;
> +
> +	case MEM_TYPE_DDR4:
> +		mt = MEM_DDR4;
> +		break;
> +	}
> +
> +	return mt;
> +}
> +
> +static enum dev_type dmc520_get_dtype(struct dmc520_edac *edac)
> +{
> +	enum dev_type dt = DEV_UNKNOWN;
> +	u32 reg_val;
> +	enum dmc520_dev_width device_width;
> +
> +	reg_val = dmc520_read_reg(edac, REG_OFFSET_MEMORY_TYPE_NOW);
> +	device_width = FIELD_GET(REG_FIELD_DEVICE_WIDTH, reg_val);
> +
> +	switch (device_width) {
> +	case DEV_WIDTH_X4:
> +		dt = DEV_X4;
> +		break;
> +
> +	case DEV_WIDTH_X8:
> +		dt = DEV_X8;
> +		break;
> +
> +	case DEV_WIDTH_X16:
> +		dt = DEV_X16;
> +		break;
> +	}
> +
> +	return dt;
> +}
> +
> +static u32 dmc520_get_rank_count(void __iomem *reg_base)
> +{
> +	u32 reg_val, rank_bits;
> +
> +	reg_val = readl(reg_base + REG_OFFSET_ADDRESS_CONTROL_NOW);
> +	rank_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_RANK, reg_val);
> +
> +	return (1 << rank_bits);

	return BIT(rank_bits);

> +}
> +
> +static u64 dmc520_get_rank_size(struct dmc520_edac *edac)
> +{
> +	u32 reg_val, col_bits, row_bits, bank_bits;
> +
> +	reg_val = dmc520_read_reg(edac, REG_OFFSET_ADDRESS_CONTROL_NOW);
> +
> +	col_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_COL, reg_val) +
> +		   DRAM_ADDRESS_CONTROL_MIN_COL_BITS;
> +	row_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_ROW, reg_val) +
> +		   DRAM_ADDRESS_CONTROL_MIN_ROW_BITS;
> +	bank_bits = FIELD_GET(REG_FIELD_ADDRESS_CONTROL_BANK, reg_val);
> +
> +	return (u64)dmc520_get_memory_width(edac) << (col_bits + row_bits + bank_bits);
> +}
> +
> +static void dmc520_handle_dram_ecc_errors(struct mem_ctl_info *mci,
> +					  bool is_ce)
> +{
> +	struct ecc_error_info info;
> +	struct dmc520_edac *edac;
> +	u32 cnt;
> +	char message[EDAC_MSG_BUF_SIZE];
> +
> +	edac = mci->pvt_info;
> +	dmc520_get_dram_ecc_error_info(edac, is_ce, &info);
> +
> +	cnt = dmc520_get_dram_ecc_error_count(edac, is_ce);
> +
> +	if (cnt > 0) {

Save an indentation level:

	if (!cnt)
		return;

	snprintf...

> +		snprintf(message, ARRAY_SIZE(message),
> +			 "rank:%d bank:%d row:%d col:%d",
> +			 info.rank, info.bank,
> +			 info.row, info.col);
> +
> +		spin_lock(&edac->ecc_lock);
> +		edac_mc_handle_error((is_ce ? HW_EVENT_ERR_CORRECTED :
> +				     HW_EVENT_ERR_UNCORRECTED),
> +				     mci, cnt, 0, 0, 0, info.rank, -1, -1,
> +				     message, "");
> +		spin_unlock(&edac->ecc_lock);
> +	}
> +}
> +
> +static irqreturn_t dmc520_edac_dram_ecc_isr(int irq, struct mem_ctl_info *mci, bool is_ce)
> +{
> +	u32 i_mask;
> +	struct dmc520_edac *edac;
> +
> +	edac = mci->pvt_info;
> +
> +	i_mask = is_ce ? DRAM_ECC_INT_CE_BIT : DRAM_ECC_INT_UE_BIT;
> +
> +	dmc520_handle_dram_ecc_errors(mci, is_ce);
> +
> +	dmc520_write_reg(edac, i_mask, REG_OFFSET_INTERRUPT_CLR);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t
> +dmc520_edac_dram_all_isr(int irq, struct mem_ctl_info *mci, u32 interrupt_mask)
> +{
> +	struct dmc520_edac *edac;
> +	u32 status;
> +	irqreturn_t irq_ret = IRQ_NONE;
> +
> +	edac = mci->pvt_info;
> +
> +	status = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_STATUS);
> +
> +	if ((interrupt_mask & DRAM_ECC_INT_CE_BIT) &&
> +		(status & DRAM_ECC_INT_CE_BIT))
> +		irq_ret = dmc520_edac_dram_ecc_isr(irq, mci, true);
> +
> +	if ((interrupt_mask & DRAM_ECC_INT_UE_BIT) &&
> +		(status & DRAM_ECC_INT_UE_BIT))
> +		irq_ret = dmc520_edac_dram_ecc_isr(irq, mci, false);
> +
> +	/* If in the future there are more supported interrupts in a different
> +	 * platform, more condition statements can be added here for each
> +	 * interrupt flag, together with its corresponding isr implementations.
> +	 */

This comment above is useless.

Also, kernel comments style is:

	/*
	 * A sentence ending with a full-stop.
	 * Another sentence. ...
	 * More sentences. ...
	 */

> +
> +	return irq_ret;
> +}
> +
> +static void dmc520_init_csrow(struct mem_ctl_info *mci)
> +{
> +	struct csrow_info *csi;
> +	struct dimm_info *dimm;
> +	int row, ch;
> +	enum dev_type dt;
> +	enum mem_type mt;
> +	u64 rs;
> +	u32 pages_per_rank;
> +	struct dmc520_edac *edac = mci->pvt_info;
> +
> +	dt = dmc520_get_dtype(edac);
> +	mt = dmc520_get_mtype(edac);
> +	rs = dmc520_get_rank_size(edac);
> +	pages_per_rank = rs >> PAGE_SHIFT;
> +
> +	for (row = 0; row < mci->nr_csrows; row++) {
> +		csi = mci->csrows[row];
> +
> +		for (ch = 0; ch < csi->nr_channels; ch++) {
> +			dimm		= csi->channels[ch]->dimm;
> +			dimm->grain	= dmc520_get_memory_width(edac);
> +			dimm->dtype	= dt;
> +			dimm->mtype	= mt;
> +			dimm->edac_mode	= EDAC_FLAG_SECDED;
> +			dimm->nr_pages	= pages_per_rank / csi->nr_channels;
> +		}
> +	}
> +}
> +
> +static int dmc520_edac_probe(struct platform_device *pdev)
> +{
> +	struct device *dev;
> +	struct dmc520_edac *edac;
> +	struct mem_ctl_info *mci;
> +	struct edac_mc_layer layers[1];
> +	int ret, intr_index, nintr, nintr_registered = 0;
> +	struct resource *res;
> +	void __iomem *reg_base;
> +	u32 reg_val;
> +
> +	/* Parsing the device node */
> +	dev = &pdev->dev;
> +
> +	nintr = of_property_count_u32_elems(dev->of_node, "interrupt-config");
> +	if (nintr <= 0) {
> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
> +			"Invalid device node configuration: at least one interrupt "
> +			"line & config is expected.\n");

More from checkpatch:

WARNING: quoted string split across lines
#528: FILE: drivers/edac/dmc520_edac.c:436:
+                       "Invalid device node configuration: at least one interrupt "
+                       "line & config is expected.\n");

WARNING: quoted string split across lines
#535: FILE: drivers/edac/dmc520_edac.c:443:
+                       "Invalid device node configuration: # of interrupt config "
+                       "elements (%d) can not exceed %ld.\n",

WARNING: quoted string split across lines
#579: FILE: drivers/edac/dmc520_edac.c:487:
+                               "interrupt-config error: "
+                               "element %d's interrupt mask %d has overlap.\n",

WARNING: quoted string split across lines
#590: FILE: drivers/edac/dmc520_edac.c:498:
+                       "interrupt-config warning: "
+                       "interrupt mask (0x%x) is not supported by dmc520 (0x%lx).\n",


> +		return -EINVAL;
> +	}
> +
> +	if (nintr > ARRAY_SIZE(dmc520_isr_array)) {
> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
> +			"Invalid device node configuration: # of interrupt config "
> +			"elements (%d) can not exceed %ld.\n",
> +			nintr, ARRAY_SIZE(dmc520_isr_array));
> +		return -EINVAL;
> +	}
> +
> +	/* Initialize dmc520 edac */
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	reg_base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(reg_base))
> +		return PTR_ERR(reg_base);
> +
> +	if (!dmc520_is_ecc_enabled(reg_base))
> +		return -ENXIO;
> +
> +	layers[0].type = EDAC_MC_LAYER_CHIP_SELECT;
> +	layers[0].size = dmc520_get_rank_count(reg_base);
> +	layers[0].is_virt_csrow = true;
> +
> +	mci = edac_mc_alloc(dmc520_mc_idx++, ARRAY_SIZE(layers), layers,
> +			    sizeof(struct dmc520_edac) + sizeof(u32) * nintr);
> +	if (!mci) {
> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
> +			    "Failed to allocate memory for mc instance\n");
> +		return -ENOMEM;
> +	}
> +
> +	edac = mci->pvt_info;
> +	edac->reg_base = reg_base;
> +	edac->nintr = nintr;
> +	edac->interrupt_mask_all = 0;
> +	spin_lock_init(&edac->ecc_lock);

Move that checking...

> +
> +	ret = of_property_read_u32_array(dev->of_node, "interrupt-config",
> +			edac->interrupt_masks, nintr);
> +	if (ret) {
> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
> +			"Failed to get interrupt-config arrays.\n");
> +		goto err_free_mc;
> +	}
> +
> +	for (intr_index = 0; intr_index < nintr; ++intr_index) {
> +		if (edac->interrupt_mask_all & edac->interrupt_masks[intr_index]) {
> +			edac_printk(KERN_ERR, EDAC_MC,
> +				"interrupt-config error: "
> +				"element %d's interrupt mask %d has overlap.\n",
> +				intr_index, edac->interrupt_masks[intr_index]);
> +			goto err_free_mc;
> +		}
> +
> +		edac->interrupt_mask_all |= edac->interrupt_masks[intr_index];
> +	}
> +
> +	if ((edac->interrupt_mask_all | ALL_INT_MASK) != ALL_INT_MASK) {
> +		edac_printk(KERN_WARNING, EDAC_MOD_NAME,
> +			"interrupt-config warning: "
> +			"interrupt mask (0x%x) is not supported by dmc520 (0x%lx).\n",
> +			edac->interrupt_mask_all, ALL_INT_MASK);
> +	}
> +	edac->interrupt_mask_all &= ALL_INT_MASK;
> +
> +	platform_set_drvdata(pdev, mci);

... up-to-here before the edac_mc_alloc() call so that you don't have to
needlessly goto err_free_mc and free the memory you just allocated if
any of those properties reading fails. IOW, do all your hw init first
and then call edac_mc_alloc(), when you have everything needed.

> +
> +	mci->pdev = dev;
> +	mci->mtype_cap = MEM_FLAG_DDR3 | MEM_FLAG_DDR4;
> +	mci->edac_ctl_cap = EDAC_FLAG_NONE | EDAC_FLAG_SECDED;
> +	mci->edac_cap = EDAC_FLAG_SECDED;
> +	mci->scrub_cap = SCRUB_FLAG_HW_SRC;
> +	mci->scrub_mode = dmc520_get_scrub_type(edac);
> +	mci->ctl_name = EDAC_CTL_NAME;
> +	mci->dev_name = dev_name(mci->pdev);
> +	mci->mod_name = EDAC_MOD_NAME;
> +	mci->ctl_page_to_phys = NULL;
> +
> +	edac_op_state = EDAC_OPSTATE_INT;
> +
> +	dmc520_init_csrow(mci);
> +
> +	ret = edac_mc_add_mc(mci);
> +	if (ret) {
> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
> +			"Failed to register with EDAC core\n");
> +		goto err_free_mc;
> +	}
> +
> +	/* Clear interrupts, not affecting other unrelated interrupts */
> +	reg_val = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_CONTROL);
> +	dmc520_write_reg(edac, reg_val & (~(edac->interrupt_mask_all)),
> +			REG_OFFSET_INTERRUPT_CONTROL);
> +	dmc520_write_reg(edac, edac->interrupt_mask_all,
> +			REG_OFFSET_INTERRUPT_CLR);
> +
> +	for (intr_index = 0; intr_index < nintr; ++intr_index) {
> +		int irq_id = platform_get_irq(pdev, intr_index);
> +
> +		if (irq_id < 0) {
> +			edac_printk(KERN_ERR, EDAC_MC,
> +				    "Failed to get irq #%d\n", intr_index);
> +			ret = -ENODEV;
> +			goto err_free_irq;
> +		}
> +
> +		ret = devm_request_irq(&pdev->dev, irq_id,
> +				dmc520_isr_array[intr_index], IRQF_SHARED,
> +				dev_name(&pdev->dev), mci);
> +		if (ret < 0) {
> +			edac_printk(KERN_ERR, EDAC_MC,
> +				    "Failed to request irq %d\n", irq_id);
> +			goto err_free_irq;
> +		}
> +
> +		++nintr_registered;
> +	}

The same with this IRQ requesting and you'll save yourself the err_free_irq too.

> +
> +	/* Reset DRAM CE/UE counters */
> +	if (edac->interrupt_mask_all & DRAM_ECC_INT_CE_BIT)
> +		dmc520_get_dram_ecc_error_count(edac, true);
> +
> +	if (edac->interrupt_mask_all & DRAM_ECC_INT_UE_BIT)
> +		dmc520_get_dram_ecc_error_count(edac, false);
> +
> +	/* Enable interrupts, not affecting other unrelated interrupts */
> +	dmc520_write_reg(edac,
> +		reg_val | edac->interrupt_mask_all,
> +		REG_OFFSET_INTERRUPT_CONTROL);

Align at opening brace:

	dmc520_write_reg(edac, reg_val | edac->interrupt_mask_all,
			 REG_OFFSET_INTERRUPT_CONTROL);

> +
> +	return 0;
> +
> +err_free_irq:
> +	for (intr_index = 0; intr_index < nintr_registered; ++intr_index) {
> +		int irq_id = platform_get_irq(pdev, intr_index);
> +
> +		devm_free_irq(&pdev->dev, irq_id, mci);
> +	}
> +	edac_mc_del_mc(&pdev->dev);
> +err_free_mc:
> +	edac_mc_free(mci);
> +
> +	return ret;
> +}
> +
> +static int dmc520_edac_remove(struct platform_device *pdev)
> +{
> +	struct dmc520_edac *edac;
> +	struct mem_ctl_info *mci;
> +	u32 reg_val, intr_index;
> +
> +	mci = platform_get_drvdata(pdev);
> +	edac = mci->pvt_info;
> +
> +	/* Disable interrupts */
> +	reg_val = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_CONTROL);
> +	dmc520_write_reg(edac, reg_val & (~(edac->interrupt_mask_all)),
> +			REG_OFFSET_INTERRUPT_CONTROL);
> +
> +	/* free irq's */
> +	for (intr_index = 0; intr_index < edac->nintr; ++intr_index) {
> +		int irq_id = platform_get_irq(pdev, intr_index);
> +
> +		devm_free_irq(&pdev->dev, irq_id, mci);
> +	}
> +
> +	edac_mc_del_mc(&pdev->dev);
> +	edac_mc_free(mci);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id dmc520_edac_driver_id[] = {
> +	{ .compatible = "arm,dmc-520", },
> +	{ /* end of table */ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, dmc520_edac_driver_id);
> +
> +static struct platform_driver dmc520_edac_driver = {
> +	.driver = {
> +		.name = "dmc520",
> +		.of_match_table = dmc520_edac_driver_id,
> +	},
> +
> +	.probe = dmc520_edac_probe,
> +	.remove = dmc520_edac_remove
> +};
> +
> +module_platform_driver(dmc520_edac_driver);
> +
> +MODULE_AUTHOR(

No linebreaks like that - let it stick out over 80 cols.

> +	"Rui Zhao <ruizhao@microsoft.com>, Lei Wang <lewan@microsoft.com>");
> +MODULE_DESCRIPTION("DMC-520 ECC driver");
> +MODULE_LICENSE("GPL v2");
> -- 

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH v5 2/2] EDAC: add EDAC driver for DMC520

[Lei Wang]

Thanks Borislav! I addressed most of your comments. There are a few that 
need your further feedback. Thanks!

>> +++ b/drivers/edac/dmc520_edac.c
>> @@ -0,0 +1,632 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* EDAC driver for DMC-520 */
> 
> That comment is kinda useless.
> 

Added some more comments for the file:

/*
  * dmc520_edac.c, EDAC driver for DMC-520 memory controller
  *
  * Authors:	Rui Zhao <ruizhao@microsoft.com>
  * 		Lei Wang <lewan@microsoft.com>
  */

> 
>> +{ \
>> +	struct mem_ctl_info *mci; \
>> +	struct dmc520_edac *edac; \
>> +	mci = data; \
>> +	edac = mci->pvt_info; \
>> +	return dmc520_edac_dram_all_isr(irq, mci, edac->interrupt_masks[index]); \
>> +}
>> +
>> +DECLARE_ISR(0)
>> +DECLARE_ISR(1)
>> +/* More DECLARE_ISR(index) can be added to support more interrupt lines. */
>> +
>> +irq_handler_t dmc520_isr_array[] = {
>> +	dmc520_isr_0,
>> +	dmc520_isr_1
>> +	/* More dmc520_isr_index can be added to support more interrupt lines. */
> 
> What are those comments really for?
> 

These comments tell how to potentially expand the driver functions to 
support more interrupts besides what are already here.

>> +
>> +	/* If in the future there are more supported interrupts in a different
>> +	 * platform, more condition statements can be added here for each
>> +	 * interrupt flag, together with its corresponding isr implementations.
>> +	 */
> 
> This comment above is useless.
> 
> Also, kernel comments style is:
> 
> 	/*
> 	 * A sentence ending with a full-stop.
> 	 * Another sentence. ...
> 	 * More sentences. ...
> 	 */
>

As above comments, this comment is to guide potential future adding to 
this driver to support other interrupts. I modified the comment format.

>> +
>> +	mci = edac_mc_alloc(dmc520_mc_idx++, ARRAY_SIZE(layers), layers,
>> +			    sizeof(struct dmc520_edac) + sizeof(u32) * nintr);
>> +	if (!mci) {
>> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
>> +			    "Failed to allocate memory for mc instance\n");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	edac = mci->pvt_info;
>> +	edac->reg_base = reg_base;
>> +	edac->nintr = nintr;
>> +	edac->interrupt_mask_all = 0;
>> +	spin_lock_init(&edac->ecc_lock);
> 
> Move that checking...
> 
>> +
>> +	ret = of_property_read_u32_array(dev->of_node, "interrupt-config",
>> +			edac->interrupt_masks, nintr);
>> +	if (ret) {
>> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
>> +			"Failed to get interrupt-config arrays.\n");
>> +		goto err_free_mc;
>> +	}
>> +
>> +	for (intr_index = 0; intr_index < nintr; ++intr_index) {
>> +		if (edac->interrupt_mask_all & edac->interrupt_masks[intr_index]) {
>> +			edac_printk(KERN_ERR, EDAC_MC,
>> +				"interrupt-config error: "
>> +				"element %d's interrupt mask %d has overlap.\n",
>> +				intr_index, edac->interrupt_masks[intr_index]);
>> +			goto err_free_mc;
>> +		}
>> +
>> +		edac->interrupt_mask_all |= edac->interrupt_masks[intr_index];
>> +	}
>> +
>> +	if ((edac->interrupt_mask_all | ALL_INT_MASK) != ALL_INT_MASK) {
>> +		edac_printk(KERN_WARNING, EDAC_MOD_NAME,
>> +			"interrupt-config warning: "
>> +			"interrupt mask (0x%x) is not supported by dmc520 (0x%lx).\n",
>> +			edac->interrupt_mask_all, ALL_INT_MASK);
>> +	}
>> +	edac->interrupt_mask_all &= ALL_INT_MASK;
>> +
>> +	platform_set_drvdata(pdev, mci);
> 
> ... up-to-here before the edac_mc_alloc() call so that you don't have to
> needlessly goto err_free_mc and free the memory you just allocated if
> any of those properties reading fails. IOW, do all your hw init first
> and then call edac_mc_alloc(), when you have everything needed.
> 

After edac_mc_alloc(), if succeeds, the above code updates dmc520_edac 
struct data. If moving edac_mc_alloc as suggested, I will need to use 
local variables to store the data, and then after edac_mc_alloc() update 
the dmc520_edac. By ordering this way, the dmc520_edac can be updated 
directly.

Planning not fix.

>> +
>> +	mci->pdev = dev;
>> +	mci->mtype_cap = MEM_FLAG_DDR3 | MEM_FLAG_DDR4;
>> +	mci->edac_ctl_cap = EDAC_FLAG_NONE | EDAC_FLAG_SECDED;
>> +	mci->edac_cap = EDAC_FLAG_SECDED;
>> +	mci->scrub_cap = SCRUB_FLAG_HW_SRC;
>> +	mci->scrub_mode = dmc520_get_scrub_type(edac);
>> +	mci->ctl_name = EDAC_CTL_NAME;
>> +	mci->dev_name = dev_name(mci->pdev);
>> +	mci->mod_name = EDAC_MOD_NAME;
>> +	mci->ctl_page_to_phys = NULL;
>> +
>> +	edac_op_state = EDAC_OPSTATE_INT;
>> +
>> +	dmc520_init_csrow(mci);
>> +
>> +	ret = edac_mc_add_mc(mci);
>> +	if (ret) {
>> +		edac_printk(KERN_ERR, EDAC_MOD_NAME,
>> +			"Failed to register with EDAC core\n");
>> +		goto err_free_mc;
>> +	}
>> +
>> +	/* Clear interrupts, not affecting other unrelated interrupts */
>> +	reg_val = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_CONTROL);
>> +	dmc520_write_reg(edac, reg_val & (~(edac->interrupt_mask_all)),
>> +			REG_OFFSET_INTERRUPT_CONTROL);
>> +	dmc520_write_reg(edac, edac->interrupt_mask_all,
>> +			REG_OFFSET_INTERRUPT_CLR);
>> +
>> +	for (intr_index = 0; intr_index < nintr; ++intr_index) {
>> +		int irq_id = platform_get_irq(pdev, intr_index);
>> +
>> +		if (irq_id < 0) {
>> +			edac_printk(KERN_ERR, EDAC_MC,
>> +				    "Failed to get irq #%d\n", intr_index);
>> +			ret = -ENODEV;
>> +			goto err_free_irq;
>> +		}
>> +
>> +		ret = devm_request_irq(&pdev->dev, irq_id,
>> +				dmc520_isr_array[intr_index], IRQF_SHARED,
>> +				dev_name(&pdev->dev), mci);
>> +		if (ret < 0) {
>> +			edac_printk(KERN_ERR, EDAC_MC,
>> +				    "Failed to request irq %d\n", irq_id);
>> +			goto err_free_irq;
>> +		}
>> +
>> +		++nintr_registered;
>> +	}
> 
> The same with this IRQ requesting and you'll save yourself the err_free_irq too.

Do you mean having an array to keep all the irq_id, and then only 
devm_request_irq on them if all of the platform_get_irq are success? Yes 
that was one option I was thinking too when writing this part. But the # 
of interrupts are not fixed and are read from the dt configuration and I 
didn't want to use a fixed MAX array size for it. Also it adds a local 
array to store the irq_id's. So eventually I favored this 
implementation: platform_get_irq one interrupt, and devm_request_irq one 
interrupt, in a loop.

Planning not fix.



Thanks again!

-Lei

Re: [PATCH v5 2/2] EDAC: add EDAC driver for DMC520

[Borislav Petkov]

On Tue, Aug 13, 2019 at 01:05:02AM +0000, Lei Wang wrote:
> Added some more comments for the file:
> 
> /*
>   * dmc520_edac.c, EDAC driver for DMC-520 memory controller
      ^^^^^^^^^^^^^

Filename is redundant.

> These comments tell how to potentially expand the driver functions to 
> support more interrupts besides what are already here.

I can read that - the question is why are they there and for whom? For
your future colleagues who'll take over this driver or what is those
comments' purpose?

> As above comments, this comment is to guide potential future adding to 
> this driver to support other interrupts.

See question above.

> After edac_mc_alloc(), if succeeds, the above code updates dmc520_edac 
> struct data. If moving edac_mc_alloc as suggested, I will need to use 
> local variables to store the data,

Yes, do that pls.

> Do you mean having an array to keep all the irq_id, and then only 
> devm_request_irq on them if all of the platform_get_irq are success?

No, move it before edac_mc_alloc().

In general, do *all* initialization of your hardware first and only
then, when it succeeds, allocate the EDAC structures.

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH v5 2/2] EDAC: add EDAC driver for DMC520

[Lei Wang]

>> These comments tell how to potentially expand the driver functions to
>> support more interrupts besides what are already here.
> 
> I can read that - the question is why are they there and for whom? For
> your future colleagues who'll take over this driver or what is those
> comments' purpose?
> 

Yes, this is to help open source developers who potentially might want 
to expand this driver, most likely colleagues, and possibly other 
developers.

>> After edac_mc_alloc(), if succeeds, the above code updates dmc520_edac
>> struct data. If moving edac_mc_alloc as suggested, I will need to use
>> local variables to store the data,
> 
> Yes, do that pls.
> 
>> Do you mean having an array to keep all the irq_id, and then only
>> devm_request_irq on them if all of the platform_get_irq are success?
> 
> No, move it before edac_mc_alloc().
> 
> In general, do *all* initialization of your hardware first and only
> then, when it succeeds, allocate the EDAC structures.
> 

Thanks! I'll address this feedback.

-Lei

Re: [PATCH v5 2/2] EDAC: add EDAC driver for DMC520

[Borislav Petkov]

On Tue, Aug 27, 2019 at 01:49:29AM +0000, Lei Wang wrote:
> Yes, this is to help open source developers who potentially might want 
> to expand this driver, most likely colleagues, and possibly other 
> developers.

Then please put that info in the comment at the beginning of the driver
- not some random single sentences about what can be done, interspersed
throughout the code. It needs to be visible at a first glance.

Also, if you want this to be a longer doc, I wouldn't mind at all having
it in Documentation/edac/ (which doesn't exist yet) and then point
people to it from the comment at the beginning of the driver.

Thx.

-- 
Regards/Gruss,
    Boris.

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