diff options
| -rw-r--r-- | drivers/nvmem/Kconfig | 8 | ||||
| -rw-r--r-- | drivers/nvmem/Makefile | 2 | ||||
| -rw-r--r-- | drivers/nvmem/rmem.c | 97 | ||||
| -rw-r--r-- | drivers/of/platform.c | 1 |
4 files changed, 108 insertions, 0 deletions
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig index 954d3b4a52ab..fecc19b884bf 100644 --- 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 diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile index a7c377218341..5376b8e0dae5 100644 --- a/drivers/nvmem/Makefile +++ b/drivers/nvmem/Makefile @@ -55,3 +55,5 @@ obj-$(CONFIG_NVMEM_ZYNQMP) += nvmem_zynqmp_nvmem.o nvmem_zynqmp_nvmem-y := zynqmp_nvmem.o obj-$(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 diff --git a/drivers/nvmem/rmem.c b/drivers/nvmem/rmem.c new file mode 100644 index 000000000000..b11c3c974b3d --- /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"); diff --git a/drivers/of/platform.c b/drivers/of/platform.c index 79bd5f5a1bf1..6699cdbe58b6 100644 --- a/drivers/of/platform.c +++ b/drivers/of/platform.c @@ -511,6 +511,7 @@ static const struct of_device_id reserved_mem_matches[] = { { .compatible = "qcom,rmtfs-mem" }, { .compatible = "qcom,cmd-db" }, { .compatible = "ramoops" }, + { .compatible = "nvmem-rmem" }, {} }; |