bcm53xx: add support for reading NVRAM based on DT mapping

This is required for devices that use NVRAM data for detecting currently
used firmware partition (e.g. Linksys devices).

Signed-off-by: Rafał Miłecki <[email protected]>

target/linux/bcm53xx/patches-5.4/181-0001-dt-bindings-firmware-add-Broadcom-s-NVRAM-memory-map.patch

@@ -0,0 +1,56 @@
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <[email protected]>
+Date: Tue, 2 Mar 2021 08:23:35 +0100
+Subject: [PATCH] dt-bindings: firmware: add Broadcom's NVRAM memory mapping
+
+NVRAM structure contains device data and can be accessed using MMIO.
+
+Signed-off-by: Rafał Miłecki <[email protected]>
+---
+ .../bindings/firmware/brcm,nvram.yaml         | 41 +++++++++++++++++++
+ 1 file changed, 41 insertions(+)
+ create mode 100644 Documentation/devicetree/bindings/firmware/brcm,nvram.yaml
+
+--- /dev/null
++++ b/Documentation/devicetree/bindings/firmware/brcm,nvram.yaml
+@@ -0,0 +1,41 @@
++# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
++%YAML 1.2
++---
++$id: "http://devicetree.org/schemas/firmware/brcm,nvram.yaml#"
++$schema: "http://devicetree.org/meta-schemas/core.yaml#"
++
++title: Broadcom's NVRAM
++
++maintainers:
++  - Rafał Miłecki <[email protected]>
++
++description: |
++  NVRAM is a structure containing device specific environment variables.
++  It is used for storing device configuration, booting parameters and
++  calibration data.
++
++  It's required very early in booting process and so is made available
++  using memory mapping.
++
++  NVRAM can be found on Broadcom BCM47xx MIPS, Northstar ARM Cortex-A9
++  and some more devices.
++
++properties:
++  compatible:
++    const: brcm,nvram
++
++  reg:
++    description: memory region with NVRAM data
++    maxItems: 1
++
++required:
++  - reg
++
++additionalProperties: false
++
++examples:
++  - |
++    nvram@1e000000 {
++         compatible = "brcm,nvram";
++         reg = <0x1e000000 0x10000>;
++    };

target/linux/bcm53xx/patches-5.4/181-0002-firmware-bcm47xx_nvram-support-platform-device-brcm-.patch

@@ -0,0 +1,85 @@
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <[email protected]>
+Date: Tue, 2 Mar 2021 08:33:13 +0100
+Subject: [PATCH] firmware: bcm47xx_nvram: support platform device "brcm,nvram"
+
+Add support for platform device providing mapping resource. This allows
+reading NVRAM based on DT mapping binding. It's required for devices
+that boot depending on NVRAM stored setup and provides early access to
+NVRAM data.
+
+Signed-off-by: Rafał Miłecki <[email protected]>
+---
+ drivers/firmware/broadcom/bcm47xx_nvram.c | 55 +++++++++++++++++++++++
+ 1 file changed, 55 insertions(+)
+
+--- a/drivers/firmware/broadcom/bcm47xx_nvram.c
++++ b/drivers/firmware/broadcom/bcm47xx_nvram.c
+@@ -13,6 +13,7 @@
+ #include <linux/kernel.h>
+ #include <linux/string.h>
+ #include <linux/mtd/mtd.h>
++#include <linux/platform_device.h>
+ #include <linux/bcm47xx_nvram.h>
+ 
+ #define NVRAM_MAGIC			0x48534C46	/* 'FLSH' */
+@@ -162,6 +163,60 @@ static int nvram_init(void)
+ 	return -ENXIO;
+ }
+ 
++static int brcm_nvram_probe(struct platform_device *pdev)
++{
++	struct nvram_header __iomem *header;
++	struct device *dev = &pdev->dev;
++	struct resource *res;
++	void __iomem *mmio;
++	size_t copy_len;
++
++	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
++	if (!res) {
++		dev_err(dev, "Failed to get resource\n");
++		return -ENODEV;
++	}
++
++	mmio = ioremap(res->start, resource_size(res));
++	if (!mmio)
++		return -ENOMEM;
++
++	header = (struct nvram_header *)mmio;
++	copy_len = DIV_ROUND_UP(sizeof(*header) + header->len, 4);
++	if (header->magic != NVRAM_MAGIC) {
++		dev_err(dev, "No NVRAM found at %pR\n", res);
++		return -EPROTO;
++	} else if (copy_len > resource_size(res)) {
++		dev_err(dev, "NVRAM size exceeds %pR\n", res);
++		return -ERANGE;
++	} else if (copy_len >= NVRAM_SPACE) {
++		dev_err(dev, "NVRAM size exceeds buffer size %d\n", NVRAM_SPACE);
++		return -ENOMEM;
++	}
++
++	__ioread32_copy(nvram_buf, mmio, copy_len);
++	nvram_buf[NVRAM_SPACE - 1] = '\0';
++
++	iounmap(mmio);
++
++	return 0;
++}
++
++static const struct of_device_id brcm_nvram_of_match[] = {
++	{ .compatible = "brcm,nvram "},
++	{},
++};
++
++static struct platform_driver brcm_nvram_driver = {
++	.driver = {
++		.name = "brcm_nvram",
++		.of_match_table = brcm_nvram_of_match,
++	},
++	.probe	= brcm_nvram_probe,
++};
++
++module_platform_driver(brcm_nvram_driver);
++
+ int bcm47xx_nvram_getenv(const char *name, char *val, size_t val_len)
+ {
+ 	char *var, *value, *end, *eq;