diff options
Diffstat (limited to 'target/linux/bcm27xx/patches-5.10/950-0446-nvmem-Add-driver-to-expose-reserved-memory-as-nvmem.patch')
| -rw-r--r-- | target/linux/bcm27xx/patches-5.10/950-0446-nvmem-Add-driver-to-expose-reserved-memory-as-nvmem.patch | 163 |
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" }, + {} + }; + |