EDAC: Add an EDAC driver for the Loongson memory controller

Add ECC support for Loongson SoC DDR controller. This driver reports single
bit errors (CE) only.

Only ACPI firmware is supported.

[ bp: Document what last_ce_count is for. ]

Signed-off-by: Zhao Qunqin <[e-mail]>
Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Reviewed-by: Huacai Chen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Borislav Petkov (AMD) <[e-mail]>

MAINTAINERS

···
 F:	Documentation/devicetree/bindings/thermal/loongson,ls2k-thermal.yaml
 F:	drivers/thermal/loongson2_thermal.c
 
+LOONGSON EDAC DRIVER
+M:	Zhao Qunqin <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	drivers/edac/loongson_edac.c
+
 LSILOGIC MPT FUSION DRIVERS (FC/SAS/SPI)
 M:	Sathya Prakash <[e-mail]>
 M:	Sreekanth Reddy <[e-mail]>

arch/loongarch/Kconfig

···
 	select BUILDTIME_TABLE_SORT
 	select COMMON_CLK
 	select CPU_PM
+	select EDAC_SUPPORT
 	select EFI
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CMOS_UPDATE

drivers/edac/Kconfig

···
 	  Support injecting both correctable and uncorrectable errors
 	  for debugging purposes.
 
+config EDAC_LOONGSON
+	tristate "Loongson Memory Controller"
+	depends on LOONGARCH && ACPI
+	help
+	  Support for error detection and correction on the Loongson
+	  family memory controller. This driver reports single bit
+	  errors (CE) only. Loongson-3A5000/3C5000/3D5000/3A6000/3C6000
+	  are compatible.
 
 endif # EDAC

drivers/edac/Makefile

···
 obj-$(CONFIG_EDAC_NPCM)			+= npcm_edac.o
 obj-$(CONFIG_EDAC_ZYNQMP)		+= zynqmp_edac.o
 obj-$(CONFIG_EDAC_VERSAL)		+= versal_edac.o
+obj-$(CONFIG_EDAC_LOONGSON)		+= loongson_edac.o

drivers/edac/loongson_edac.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Loongson Technology Corporation Limited.
+ */
+
+#include <linux/acpi.h>
+#include <linux/edac.h>
+#include <linux/init.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include "edac_module.h"
+
+#define ECC_CS_COUNT_REG	0x18
+
+struct loongson_edac_pvt {
+	void __iomem *ecc_base;
+
+	/*
+	 * The ECC register in this controller records the number of errors
+	 * encountered since reset and cannot be zeroed so in order to be able
+	 * to report the error count at each check, this records the previous
+	 * register state.
+	 */
+	int last_ce_count;
+};
+
+static int read_ecc(struct mem_ctl_info *mci)
+{
+	struct loongson_edac_pvt *pvt = mci->pvt_info;
+	u64 ecc;
+	int cs;
+
+	ecc = readq(pvt->ecc_base + ECC_CS_COUNT_REG);
+	/* cs0 -- cs3 */
+	cs = ecc & 0xff;
+	cs += (ecc >> 8) & 0xff;
+	cs += (ecc >> 16) & 0xff;
+	cs += (ecc >> 24) & 0xff;
+
+	return cs;
+}
+
+static void edac_check(struct mem_ctl_info *mci)
+{
+	struct loongson_edac_pvt *pvt = mci->pvt_info;
+	int new, add;
+
+	new = read_ecc(mci);
+	add = new - pvt->last_ce_count;
+	pvt->last_ce_count = new;
+	if (add <= 0)
+		return;
+
+	edac_mc_handle_error(HW_EVENT_ERR_CORRECTED, mci, add,
+			     0, 0, 0, 0, 0, -1, "error", "");
+}
+
+static void dimm_config_init(struct mem_ctl_info *mci)
+{
+	struct dimm_info *dimm;
+	u32 size, npages;
+
+	/* size not used */
+	size = -1;
+	npages = MiB_TO_PAGES(size);
+
+	dimm = edac_get_dimm(mci, 0, 0, 0);
+	dimm->nr_pages = npages;
+	snprintf(dimm->label, sizeof(dimm->label),
+		 "MC#%uChannel#%u_DIMM#%u", mci->mc_idx, 0, 0);
+	dimm->grain = 8;
+}
+
+static void pvt_init(struct mem_ctl_info *mci, void __iomem *vbase)
+{
+	struct loongson_edac_pvt *pvt = mci->pvt_info;
+
+	pvt->ecc_base = vbase;
+	pvt->last_ce_count = read_ecc(mci);
+}
+
+static int edac_probe(struct platform_device *pdev)
+{
+	struct edac_mc_layer layers[2];
+	struct mem_ctl_info *mci;
+	void __iomem *vbase;
+	int ret;
+
+	vbase = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(vbase))
+		return PTR_ERR(vbase);
+
+	layers[0].type = EDAC_MC_LAYER_CHANNEL;
+	layers[0].size = 1;
+	layers[0].is_virt_csrow = false;
+	layers[1].type = EDAC_MC_LAYER_SLOT;
+	layers[1].size = 1;
+	layers[1].is_virt_csrow = true;
+	mci = edac_mc_alloc(0, ARRAY_SIZE(layers), layers,
+			    sizeof(struct loongson_edac_pvt));
+	if (mci == NULL)
+		return -ENOMEM;
+
+	mci->mc_idx = edac_device_alloc_index();
+	mci->mtype_cap = MEM_FLAG_RDDR4;
+	mci->edac_ctl_cap = EDAC_FLAG_NONE;
+	mci->edac_cap = EDAC_FLAG_NONE;
+	mci->mod_name = "loongson_edac.c";
+	mci->ctl_name = "loongson_edac_ctl";
+	mci->dev_name = "loongson_edac_dev";
+	mci->ctl_page_to_phys = NULL;
+	mci->pdev = &pdev->dev;
+	mci->error_desc.grain = 8;
+	mci->edac_check = edac_check;
+
+	pvt_init(mci, vbase);
+	dimm_config_init(mci);
+
+	ret = edac_mc_add_mc(mci);
+	if (ret) {
+		edac_dbg(0, "MC: failed edac_mc_add_mc()\n");
+		edac_mc_free(mci);
+		return ret;
+	}
+	edac_op_state = EDAC_OPSTATE_POLL;
+
+	return 0;
+}
+
+static void edac_remove(struct platform_device *pdev)
+{
+	struct mem_ctl_info *mci = edac_mc_del_mc(&pdev->dev);
+
+	if (mci)
+		edac_mc_free(mci);
+}
+
+static const struct acpi_device_id loongson_edac_acpi_match[] = {
+	{"LOON0010", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, loongson_edac_acpi_match);
+
+static struct platform_driver loongson_edac_driver = {
+	.probe		= edac_probe,
+	.remove		= edac_remove,
+	.driver		= {
+		.name	= "loongson-mc-edac",
+		.acpi_match_table = loongson_edac_acpi_match,
+	},
+};
+module_platform_driver(loongson_edac_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Zhao Qunqin <[e-mail]>");
+MODULE_DESCRIPTION("EDAC driver for loongson memory controller");