[PATCH v2 2/4] nvmem: Add the Raspberry Pi OTP driver

[Gregor Herburger <gregor.herburger@linutronix.de>]

Raspberry Pis have OTP registers which can be accessed through the
videocore firmware. Add a nvmem driver to support these OTP registers.

Signed-off-by: Gregor Herburger <gregor.herburger@linutronix.de>
---
 drivers/nvmem/Kconfig                      |  10 +++
 drivers/nvmem/Makefile                     |   1 +
 drivers/nvmem/raspberrypi-otp.c            | 119 +++++++++++++++++++++++++++++
 include/soc/bcm2835/raspberrypi-firmware.h |   9 +++
 4 files changed, 139 insertions(+)

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 74ddbd0f79b0..4ecfb0dfbe6b 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -483,4 +483,14 @@ config NVMEM_QORIQ_EFUSE
 	  This driver can also be built as a module. If so, the module
 	  will be called nvmem_qoriq_efuse.
 
+config NVMEM_RASPBERRYPI_OTP
+	tristate "Raspberry Pi OTP support"
+	depends on RASPBERRYPI_FIRMWARE || COMPILE_TEST
+	help
+	  This driver provides access to the Raspberry Pi OTP memory via the
+	  nvmem subsystem. The driver supports the customer OTP as well as the
+	  device specific private key OTP (BCM2712 only).
+
+	  This driver can also be built as a module. If so, the module
+	  will be called raspberrypi-otp.
 endif
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 7252b8ec88d4..8ca2095e068f 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -95,3 +95,4 @@ obj-$(CONFIG_NVMEM_ZYNQMP)		+= nvmem_zynqmp_nvmem.o
 nvmem_zynqmp_nvmem-y			:= zynqmp_nvmem.o
 obj-$(CONFIG_NVMEM_QORIQ_EFUSE)		+= nvmem-qoriq-efuse.o
 nvmem-qoriq-efuse-y			:= qoriq-efuse.o
+obj-$(CONFIG_NVMEM_RASPBERRYPI_OTP)	+= raspberrypi-otp.o
diff --git a/drivers/nvmem/raspberrypi-otp.c b/drivers/nvmem/raspberrypi-otp.c
new file mode 100644
index 000000000000..83624aa85bb3
--- /dev/null
+++ b/drivers/nvmem/raspberrypi-otp.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/overflow.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+struct rpi_otp_priv {
+	struct rpi_firmware *fw;
+	struct device *dev;
+	u32 read_tag;
+	u32 write_tag;
+};
+
+struct rpi_otp_header {
+	u32 start;
+	u32 count;
+	u32 data[] __counted_by(count);
+};
+
+static int rpi_otp_read(void *context, unsigned int offset, void *buf, size_t bytes)
+{
+	struct rpi_otp_priv *priv = context;
+	struct rpi_otp_header *fwbuf;
+	u32 count = bytes / 4;
+	int ret;
+
+	fwbuf = kzalloc(struct_size(fwbuf, data, count), GFP_KERNEL);
+	if (!fwbuf)
+		return -ENOMEM;
+
+	fwbuf->start = offset / 4;
+	fwbuf->count = count;
+
+	ret = rpi_firmware_property(priv->fw, priv->read_tag, fwbuf,
+				    sizeof(struct rpi_otp_header) + bytes);
+	if (ret)
+		goto out;
+
+	memcpy(buf, fwbuf->data, bytes);
+
+out:
+	kfree(fwbuf);
+	return ret;
+}
+
+static int rpi_otp_write(void *context, unsigned int offset, void *val, size_t bytes)
+{
+	struct rpi_otp_priv *priv = context;
+	struct rpi_otp_header *fwbuf;
+	u32 count = bytes / 4;
+	int ret;
+
+	fwbuf = kzalloc(struct_size(fwbuf, data, count), GFP_KERNEL);
+	if (!fwbuf)
+		return -ENOMEM;
+
+	fwbuf->start = offset / 4;
+	fwbuf->count = count;
+	memcpy(fwbuf->data, val, bytes);
+
+	ret = rpi_firmware_property(priv->fw, priv->write_tag, fwbuf,
+				    sizeof(struct rpi_otp_header) + bytes);
+
+	kfree(fwbuf);
+	return ret;
+}
+
+static int rpi_otp_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct nvmem_device *nvmem;
+	struct rpi_otp_priv *priv;
+	const struct rpi_otp_driver_data *data;
+	struct nvmem_config config = {
+		.read_only = false,
+		.word_size = 4,
+		.stride = 4,
+		.reg_read = rpi_otp_read,
+		.reg_write = rpi_otp_write,
+		.id = NVMEM_DEVID_NONE,
+	};
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	data = dev_get_platdata(dev);
+	if (!data)
+		return -ENODEV;
+
+	priv->fw = dev_get_drvdata(dev->parent);
+	priv->dev = dev;
+	priv->read_tag = data->read_tag;
+	priv->write_tag = data->write_tag;
+	config.dev = dev;
+	config.priv = priv;
+	config.name = data->name;
+	config.size = data->size;
+
+	nvmem = devm_nvmem_register(dev, &config);
+	if (IS_ERR(nvmem))
+		return dev_err_probe(dev, PTR_ERR(nvmem), "error registering nvmem config\n");
+
+	return 0;
+}
+
+static struct platform_driver raspberry_otp_driver = {
+	.probe	= rpi_otp_probe,
+	.driver = {
+		.name	= "raspberrypi-otp",
+	},
+};
+module_platform_driver(raspberry_otp_driver);
+
+MODULE_AUTHOR("Gregor Herburger <gregor.herburger@linutronix.de>");
+MODULE_DESCRIPTION("Raspberry Pi OTP driver");
+MODULE_LICENSE("GPL");
diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
index e1f87fbfe554..ae73c9cd19ba 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -92,6 +92,8 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_SET_POE_HAT_VAL =                        0x00030050,
 	RPI_FIRMWARE_NOTIFY_XHCI_RESET =                      0x00030058,
 	RPI_FIRMWARE_NOTIFY_DISPLAY_DONE =                    0x00030066,
+	RPI_FIRMWARE_GET_PRIVATE_OTP =                        0x00030081,
+	RPI_FIRMWARE_SET_PRIVATE_OTP =                        0x00038081,
 
 	/* Dispmanx TAGS */
 	RPI_FIRMWARE_FRAMEBUFFER_ALLOCATE =                   0x00040001,
@@ -174,6 +176,13 @@ struct rpi_firmware_clk_rate_request {
 		.id = cpu_to_le32(_id),		\
 	}
 
+struct rpi_otp_driver_data {
+	const char *name;
+	u32 read_tag;
+	u32 write_tag;
+	int size;
+};
+
 #if IS_ENABLED(CONFIG_RASPBERRYPI_FIRMWARE)
 int rpi_firmware_property(struct rpi_firmware *fw,
 			  u32 tag, void *data, size_t len);

-- 
2.47.3