nvmem: Add driver for STM32 factory-programmed read only mem

Add a read only nvmem driver for STM32 factory-programmed memory area
(on-chip non-volatile storage).
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/Kconfig

@@ -113,6 +113,16 @@ config NVMEM_BCM_OCOTP
 	  This driver can also be built as a module. If so, the module
 	  will be called nvmem-bcm-ocotp.
 
+config NVMEM_STM32_ROMEM
+	tristate "STMicroelectronics STM32 factory-programmed memory support"
+	depends on ARCH_STM32 || COMPILE_TEST
+	help
+	  Say y here to enable read-only access for STMicroelectronics STM32
+	  factory-programmed memory area.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called nvmem-stm32-romem.
+
 config NVMEM_SUNXI_SID
 	tristate "Allwinner SoCs SID support"
 	depends on ARCH_SUNXI

drivers/nvmem/Makefile

@@ -26,6 +26,8 @@ nvmem_qfprom-y			:= qfprom.o
 obj-$(CONFIG_ROCKCHIP_EFUSE)	+= nvmem_rockchip_efuse.o
 nvmem_rockchip_efuse-y		:= rockchip-efuse.o
 obj-$(CONFIG_NVMEM_SUNXI_SID)	+= nvmem_sunxi_sid.o
+nvmem_stm32_romem-y 		:= stm32-romem.o
+obj-$(CONFIG_NVMEM_STM32_ROMEM) += nvmem_stm32_romem.o
 nvmem_sunxi_sid-y		:= sunxi_sid.o
 obj-$(CONFIG_UNIPHIER_EFUSE)	+= nvmem-uniphier-efuse.o
 nvmem-uniphier-efuse-y		:= uniphier-efuse.o

drivers/nvmem/stm32-romem.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * STM32 Factory-programmed memory read access driver
+ *
+ * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
+ * Author: Fabrice Gasnier <fabrice.gasnier@st.com> for STMicroelectronics.
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_device.h>
+
+struct stm32_romem_priv {
+	void __iomem *base;
+	struct nvmem_config cfg;
+};
+
+static int stm32_romem_read(void *context, unsigned int offset, void *buf,
+			    size_t bytes)
+{
+	struct stm32_romem_priv *priv = context;
+	u8 *buf8 = buf;
+	int i;
+
+	for (i = offset; i < offset + bytes; i++)
+		*buf8++ = readb_relaxed(priv->base + i);
+
+	return 0;
+}
+
+static int stm32_romem_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct stm32_romem_priv *priv;
+	struct resource *res;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->cfg.name = "stm32-romem";
+	priv->cfg.read_only = true;
+	priv->cfg.word_size = 1;
+	priv->cfg.stride = 1;
+	priv->cfg.size = resource_size(res);
+	priv->cfg.reg_read = stm32_romem_read;
+	priv->cfg.dev = dev;
+	priv->cfg.priv = priv;
+	priv->cfg.owner = THIS_MODULE;
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &priv->cfg));
+}
+
+static const struct of_device_id stm32_romem_of_match[] = {
+	{ .compatible = "st,stm32f4-otp", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_romem_of_match);
+
+static struct platform_driver stm32_romem_driver = {
+	.probe = stm32_romem_probe,
+	.driver = {
+		.name = "stm32-romem",
+		.of_match_table = of_match_ptr(stm32_romem_of_match),
+	},
+};
+module_platform_driver(stm32_romem_driver);
+
+MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 RO-MEM");
+MODULE_ALIAS("platform:nvmem-stm32-romem");
+MODULE_LICENSE("GPL v2");