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-rw-r--r--target/linux/bcm27xx/patches-5.10/950-0446-nvmem-Add-driver-to-expose-reserved-memory-as-nvmem.patch163
1 files changed, 163 insertions, 0 deletions
diff --git a/target/linux/bcm27xx/patches-5.10/950-0446-nvmem-Add-driver-to-expose-reserved-memory-as-nvmem.patch b/target/linux/bcm27xx/patches-5.10/950-0446-nvmem-Add-driver-to-expose-reserved-memory-as-nvmem.patch
new file mode 100644
index 0000000000..79fc84f5ac
--- /dev/null
+++ b/target/linux/bcm27xx/patches-5.10/950-0446-nvmem-Add-driver-to-expose-reserved-memory-as-nvmem.patch
@@ -0,0 +1,163 @@
+From 639949895123bb937b374ccacae0675ff4ab6e55 Mon Sep 17 00:00:00 2001
+From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+Date: Thu, 10 Dec 2020 12:13:49 +0100
+Subject: [PATCH] nvmem: Add driver to expose reserved memory as nvmem
+
+Firmware/co-processors might use reserved memory areas in order to pass
+data stemming from an nvmem device otherwise non accessible to Linux.
+For example an EEPROM memory only physically accessible to firmware, or
+data only accessible early at boot time.
+
+In order to expose this data to other drivers and user-space, the driver
+models the reserved memory area as an nvmem device.
+
+Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+
+---
+
+Changes since v1:
+ - Remove reserved memory phandle indirection by directly creating a
+ platform device from the reserved memory DT node
+ - Only map memory upon reading it to avoid corruption
+ - Small cosmetic cleanups
+---
+ drivers/nvmem/Kconfig | 8 ++++
+ drivers/nvmem/Makefile | 2 +
+ drivers/nvmem/rmem.c | 97 ++++++++++++++++++++++++++++++++++++++++++
+ drivers/of/platform.c | 1 +
+ 4 files changed, 108 insertions(+)
+ create mode 100644 drivers/nvmem/rmem.c
+
+--- a/drivers/nvmem/Kconfig
++++ b/drivers/nvmem/Kconfig
+@@ -270,4 +270,12 @@ config SPRD_EFUSE
+ This driver can also be built as a module. If so, the module
+ will be called nvmem-sprd-efuse.
+
++config NVMEM_RMEM
++ tristate "Reserved Memory Based Driver Support"
++ help
++ This drivers maps reserved memory into an nvmem device. It might be
++ useful to expose information left by firmware in memory.
++
++ This driver can also be built as a module. If so, the module
++ will be called nvmem-rmem.
+ endif
+--- a/drivers/nvmem/Makefile
++++ b/drivers/nvmem/Makefile
+@@ -55,3 +55,5 @@ obj-$(CONFIG_NVMEM_ZYNQMP) += nvmem_zynq
+ nvmem_zynqmp_nvmem-y := zynqmp_nvmem.o
+ obj-$(CONFIG_SPRD_EFUSE) += nvmem_sprd_efuse.o
+ nvmem_sprd_efuse-y := sprd-efuse.o
++obj-$(CONFIG_NVMEM_RMEM) += nvmem-rmem.o
++nvmem-rmem-y := rmem.o
+--- /dev/null
++++ b/drivers/nvmem/rmem.c
+@@ -0,0 +1,97 @@
++// SPDX-License-Identifier: GPL-2.0+
++/*
++ * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
++ */
++
++#include <linux/io.h>
++#include <linux/module.h>
++#include <linux/nvmem-provider.h>
++#include <linux/of_reserved_mem.h>
++#include <linux/platform_device.h>
++
++struct rmem {
++ struct device *dev;
++ struct nvmem_device *nvmem;
++ struct reserved_mem *mem;
++
++ phys_addr_t size;
++};
++
++static int rmem_read(void *context, unsigned int offset,
++ void *val, size_t bytes)
++{
++ struct rmem *priv = context;
++ size_t available = priv->mem->size;
++ loff_t off = offset;
++ void *addr;
++ int count;
++
++ /*
++ * Only map the reserved memory at this point to avoid potential rogue
++ * kernel threads inadvertently modifying it. Based on the current
++ * uses-cases for this driver, the performance hit isn't a concern.
++ * Nor is likely to be, given the nature of the subsystem. Most nvmem
++ * devices operate over slow buses to begin with.
++ *
++ * An alternative would be setting the memory as RO, set_memory_ro(),
++ * but as of Dec 2020 this isn't possible on arm64.
++ */
++ addr = memremap(priv->mem->base, available, MEMREMAP_WB);
++ if (IS_ERR(addr)) {
++ dev_err(priv->dev, "Failed to remap memory region\n");
++ return PTR_ERR(addr);
++ }
++
++ count = memory_read_from_buffer(val, bytes, &off, addr, available);
++
++ memunmap(addr);
++
++ return count;
++}
++
++static int rmem_probe(struct platform_device *pdev)
++{
++ struct nvmem_config config = { };
++ struct device *dev = &pdev->dev;
++ struct reserved_mem *mem;
++ struct rmem *priv;
++
++ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
++ if (!priv)
++ return -ENOMEM;
++ priv->dev = dev;
++
++ mem = of_reserved_mem_lookup(dev->of_node);
++ if (!mem) {
++ dev_err(dev, "Failed to lookup reserved memory\n");
++ return -EINVAL;
++ }
++ priv->mem = mem;
++
++ config.dev = dev;
++ config.priv = priv;
++ config.name = "rmem";
++ config.size = mem->size;
++ config.reg_read = rmem_read;
++
++ return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
++}
++
++static const struct of_device_id rmem_match[] = {
++ { .compatible = "nvmem-rmem", },
++ { /* sentinel */ },
++};
++MODULE_DEVICE_TABLE(of, rmem_match);
++
++static struct platform_driver rmem_driver = {
++ .probe = rmem_probe,
++ .driver = {
++ .name = "rmem",
++ .of_match_table = rmem_match,
++ },
++};
++module_platform_driver(rmem_driver);
++
++MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
++MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
++MODULE_LICENSE("GPL");
+--- a/drivers/of/platform.c
++++ b/drivers/of/platform.c
+@@ -511,6 +511,7 @@ static const struct of_device_id reserve
+ { .compatible = "qcom,rmtfs-mem" },
+ { .compatible = "qcom,cmd-db" },
+ { .compatible = "ramoops" },
++ { .compatible = "nvmem-rmem" },
+ {}
+ };
+