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39c115028a
Fixes: 4efa0b70d5 ("kernel: backport U-Boot environment data NVMEM driver")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
165 lines
4.7 KiB
Diff
165 lines
4.7 KiB
Diff
From 639949895123bb937b374ccacae0675ff4ab6e55 Mon Sep 17 00:00:00 2001
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From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
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Date: Thu, 10 Dec 2020 12:13:49 +0100
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Subject: [PATCH] nvmem: Add driver to expose reserved memory as nvmem
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Firmware/co-processors might use reserved memory areas in order to pass
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data stemming from an nvmem device otherwise non accessible to Linux.
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For example an EEPROM memory only physically accessible to firmware, or
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data only accessible early at boot time.
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In order to expose this data to other drivers and user-space, the driver
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models the reserved memory area as an nvmem device.
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Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
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---
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Changes since v1:
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- Remove reserved memory phandle indirection by directly creating a
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platform device from the reserved memory DT node
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- Only map memory upon reading it to avoid corruption
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- Small cosmetic cleanups
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---
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drivers/nvmem/Kconfig | 8 ++++
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drivers/nvmem/Makefile | 2 +
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drivers/nvmem/rmem.c | 97 ++++++++++++++++++++++++++++++++++++++++++
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drivers/of/platform.c | 1 +
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4 files changed, 108 insertions(+)
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create mode 100644 drivers/nvmem/rmem.c
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--- a/drivers/nvmem/Kconfig
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+++ b/drivers/nvmem/Kconfig
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@@ -283,4 +283,13 @@ config NVMEM_U_BOOT_ENV
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If compiled as module it will be called nvmem_u-boot-env.
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+config NVMEM_RMEM
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+ tristate "Reserved Memory Based Driver Support"
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+ help
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+ This drivers maps reserved memory into an nvmem device. It might be
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+ useful to expose information left by firmware in memory.
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+
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+ This driver can also be built as a module. If so, the module
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+ will be called nvmem-rmem.
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+
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endif
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--- a/drivers/nvmem/Makefile
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+++ b/drivers/nvmem/Makefile
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@@ -57,3 +57,5 @@ obj-$(CONFIG_SPRD_EFUSE) += nvmem_sprd_e
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nvmem_sprd_efuse-y := sprd-efuse.o
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obj-$(CONFIG_NVMEM_U_BOOT_ENV) += nvmem_u-boot-env.o
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nvmem_u-boot-env-y := u-boot-env.o
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+obj-$(CONFIG_NVMEM_RMEM) += nvmem-rmem.o
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+nvmem-rmem-y := rmem.o
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--- /dev/null
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+++ b/drivers/nvmem/rmem.c
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@@ -0,0 +1,97 @@
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+// SPDX-License-Identifier: GPL-2.0+
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+/*
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+ * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
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+ */
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+
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+#include <linux/io.h>
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+#include <linux/module.h>
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+#include <linux/nvmem-provider.h>
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+#include <linux/of_reserved_mem.h>
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+#include <linux/platform_device.h>
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+
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+struct rmem {
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+ struct device *dev;
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+ struct nvmem_device *nvmem;
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+ struct reserved_mem *mem;
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+
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+ phys_addr_t size;
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+};
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+
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+static int rmem_read(void *context, unsigned int offset,
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+ void *val, size_t bytes)
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+{
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+ struct rmem *priv = context;
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+ size_t available = priv->mem->size;
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+ loff_t off = offset;
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+ void *addr;
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+ int count;
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+
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+ /*
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+ * Only map the reserved memory at this point to avoid potential rogue
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+ * kernel threads inadvertently modifying it. Based on the current
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+ * uses-cases for this driver, the performance hit isn't a concern.
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+ * Nor is likely to be, given the nature of the subsystem. Most nvmem
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+ * devices operate over slow buses to begin with.
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+ *
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+ * An alternative would be setting the memory as RO, set_memory_ro(),
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+ * but as of Dec 2020 this isn't possible on arm64.
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+ */
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+ addr = memremap(priv->mem->base, available, MEMREMAP_WB);
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+ if (IS_ERR(addr)) {
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+ dev_err(priv->dev, "Failed to remap memory region\n");
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+ return PTR_ERR(addr);
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+ }
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+
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+ count = memory_read_from_buffer(val, bytes, &off, addr, available);
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+
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+ memunmap(addr);
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+
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+ return count;
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+}
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+
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+static int rmem_probe(struct platform_device *pdev)
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+{
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+ struct nvmem_config config = { };
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+ struct device *dev = &pdev->dev;
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+ struct reserved_mem *mem;
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+ struct rmem *priv;
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+
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+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
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+ if (!priv)
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+ return -ENOMEM;
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+ priv->dev = dev;
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+
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+ mem = of_reserved_mem_lookup(dev->of_node);
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+ if (!mem) {
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+ dev_err(dev, "Failed to lookup reserved memory\n");
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+ return -EINVAL;
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+ }
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+ priv->mem = mem;
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+
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+ config.dev = dev;
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+ config.priv = priv;
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+ config.name = "rmem";
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+ config.size = mem->size;
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+ config.reg_read = rmem_read;
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+
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+ return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
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+}
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+
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+static const struct of_device_id rmem_match[] = {
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+ { .compatible = "nvmem-rmem", },
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+ { /* sentinel */ },
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+};
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+MODULE_DEVICE_TABLE(of, rmem_match);
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+
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+static struct platform_driver rmem_driver = {
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+ .probe = rmem_probe,
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+ .driver = {
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+ .name = "rmem",
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+ .of_match_table = rmem_match,
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+ },
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+};
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+module_platform_driver(rmem_driver);
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+
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+MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
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+MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
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+MODULE_LICENSE("GPL");
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--- a/drivers/of/platform.c
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+++ b/drivers/of/platform.c
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@@ -511,6 +511,7 @@ static const struct of_device_id reserve
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{ .compatible = "qcom,rmtfs-mem" },
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{ .compatible = "qcom,cmd-db" },
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{ .compatible = "ramoops" },
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+ { .compatible = "nvmem-rmem" },
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{}
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};
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