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Diffstat (limited to 'drivers/nvmem/rmem.c')
-rw-r--r--drivers/nvmem/rmem.c97
1 files changed, 97 insertions, 0 deletions
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");