mtd: add driver for intel graphics non-volatile memory device

Add auxiliary driver for intel discrete graphics
non-volatile memory device.

CC: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Co-developed-by: Tomas Winkler <tomasw@gmail.com>
Signed-off-by: Tomas Winkler <tomasw@gmail.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Link: https://lore.kernel.org/r/20250617145159.3803852-2-alexander.usyskin@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

MAINTAINERS

@@ -12086,6 +12086,13 @@ L:	linux-kernel@vger.kernel.org
 S:	Supported
 F:	arch/x86/include/asm/intel-family.h
 
+INTEL DISCRETE GRAPHICS NVM MTD DRIVER
+M:	Alexander Usyskin <alexander.usyskin@intel.com>
+L:	linux-mtd@lists.infradead.org
+S:	Supported
+F:	drivers/mtd/devices/mtd_intel_dg.c
+F:	include/linux/intel_dg_nvm_aux.h
+
 INTEL DRM DISPLAY FOR XE AND I915 DRIVERS
 M:	Jani Nikula <jani.nikula@linux.intel.com>
 M:	Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/mtd/devices/Kconfig

@@ -183,6 +183,17 @@ config MTD_POWERNV_FLASH
 	  platforms from Linux. This device abstracts away the
 	  firmware interface for flash access.
 
+config MTD_INTEL_DG
+	tristate "Intel Discrete Graphics non-volatile memory driver"
+	depends on AUXILIARY_BUS
+	depends on MTD
+	help
+	  This provides an MTD device to access Intel Discrete Graphics
+	  non-volatile memory.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called mtd-intel-dg.
+
 comment "Disk-On-Chip Device Drivers"
 
 config MTD_DOCG3

drivers/mtd/devices/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_MTD_SST25L)	+= sst25l.o
 obj-$(CONFIG_MTD_BCM47XXSFLASH)	+= bcm47xxsflash.o
 obj-$(CONFIG_MTD_ST_SPI_FSM)    += st_spi_fsm.o
 obj-$(CONFIG_MTD_POWERNV_FLASH)	+= powernv_flash.o
+obj-$(CONFIG_MTD_INTEL_DG)	+= mtd_intel_dg.o
 
 
 CFLAGS_docg3.o			+= -I$(src)

drivers/mtd/devices/mtd_intel_dg.c

@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright(c) 2019-2025, Intel Corporation. All rights reserved.
+ */
+
+#include <linux/device.h>
+#include <linux/intel_dg_nvm_aux.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+struct intel_dg_nvm {
+	struct kref refcnt;
+	void __iomem *base;
+	size_t size;
+	unsigned int nregions;
+	struct {
+		const char *name;
+		u8 id;
+		u64 offset;
+		u64 size;
+	} regions[] __counted_by(nregions);
+};
+
+static void intel_dg_nvm_release(struct kref *kref)
+{
+	struct intel_dg_nvm *nvm = container_of(kref, struct intel_dg_nvm, refcnt);
+	int i;
+
+	pr_debug("freeing intel_dg nvm\n");
+	for (i = 0; i < nvm->nregions; i++)
+		kfree(nvm->regions[i].name);
+	kfree(nvm);
+}
+
+static int intel_dg_mtd_probe(struct auxiliary_device *aux_dev,
+			      const struct auxiliary_device_id *aux_dev_id)
+{
+	struct intel_dg_nvm_dev *invm = auxiliary_dev_to_intel_dg_nvm_dev(aux_dev);
+	struct intel_dg_nvm *nvm;
+	struct device *device;
+	unsigned int nregions;
+	unsigned int i, n;
+	int ret;
+
+	device = &aux_dev->dev;
+
+	/* count available regions */
+	for (nregions = 0, i = 0; i < INTEL_DG_NVM_REGIONS; i++) {
+		if (invm->regions[i].name)
+			nregions++;
+	}
+
+	if (!nregions) {
+		dev_err(device, "no regions defined\n");
+		return -ENODEV;
+	}
+
+	nvm = kzalloc(struct_size(nvm, regions, nregions), GFP_KERNEL);
+	if (!nvm)
+		return -ENOMEM;
+
+	kref_init(&nvm->refcnt);
+
+	for (n = 0, i = 0; i < INTEL_DG_NVM_REGIONS; i++) {
+		if (!invm->regions[i].name)
+			continue;
+
+		char *name = kasprintf(GFP_KERNEL, "%s.%s",
+				       dev_name(&aux_dev->dev), invm->regions[i].name);
+		if (!name)
+			continue;
+		nvm->regions[n].name = name;
+		nvm->regions[n].id = i;
+		n++;
+	}
+	nvm->nregions = n; /* in case where kasprintf fail */
+
+	nvm->base = devm_ioremap_resource(device, &invm->bar);
+	if (IS_ERR(nvm->base)) {
+		ret = PTR_ERR(nvm->base);
+		goto err;
+	}
+
+	dev_set_drvdata(&aux_dev->dev, nvm);
+
+	return 0;
+
+err:
+	kref_put(&nvm->refcnt, intel_dg_nvm_release);
+	return ret;
+}
+
+static void intel_dg_mtd_remove(struct auxiliary_device *aux_dev)
+{
+	struct intel_dg_nvm *nvm = dev_get_drvdata(&aux_dev->dev);
+
+	if (!nvm)
+		return;
+
+	dev_set_drvdata(&aux_dev->dev, NULL);
+
+	kref_put(&nvm->refcnt, intel_dg_nvm_release);
+}
+
+static const struct auxiliary_device_id intel_dg_mtd_id_table[] = {
+	{
+		.name = "i915.nvm",
+	},
+	{
+		.name = "xe.nvm",
+	},
+	{
+		/* sentinel */
+	}
+};
+MODULE_DEVICE_TABLE(auxiliary, intel_dg_mtd_id_table);
+
+static struct auxiliary_driver intel_dg_mtd_driver = {
+	.probe  = intel_dg_mtd_probe,
+	.remove = intel_dg_mtd_remove,
+	.driver = {
+		/* auxiliary_driver_register() sets .name to be the modname */
+	},
+	.id_table = intel_dg_mtd_id_table
+};
+module_auxiliary_driver(intel_dg_mtd_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_DESCRIPTION("Intel DGFX MTD driver");

include/linux/intel_dg_nvm_aux.h

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright(c) 2019-2025, Intel Corporation. All rights reserved.
+ */
+
+#ifndef __INTEL_DG_NVM_AUX_H__
+#define __INTEL_DG_NVM_AUX_H__
+
+#include <linux/auxiliary_bus.h>
+#include <linux/container_of.h>
+#include <linux/ioport.h>
+#include <linux/types.h>
+
+#define INTEL_DG_NVM_REGIONS 13
+
+struct intel_dg_nvm_region {
+	const char *name;
+};
+
+struct intel_dg_nvm_dev {
+	struct auxiliary_device aux_dev;
+	bool writable_override;
+	struct resource bar;
+	const struct intel_dg_nvm_region *regions;
+};
+
+#define auxiliary_dev_to_intel_dg_nvm_dev(auxiliary_dev) \
+	container_of(auxiliary_dev, struct intel_dg_nvm_dev, aux_dev)
+
+#endif /* __INTEL_DG_NVM_AUX_H__ */