RFC: NVMEM driver for customer OTP

Documentation/devicetree/bindings/nvmem/raspberrypi,bcm2835-customer-otp.txt

@@ -0,0 +1,18 @@
+Customer OTP Memory for Raspberry Pi
+
+Required properties :
+- compatible : Should be "raspberrypi,bcm2835-customer-otp"
+- firmware : Reference to the RPi firmware device node.
+- #address-cells : Should be 1
+- #size-cells : Should be 1
+
+See nvmem.txt for more information.
+
+Example:
+
+ customer_otp: otp {
+ compatible = "raspberrypi,bcm2835-customer-otp";
+ firmware = <&firmware>;
+ #address-cells = <1>;
+ #size-cells = <1>;
+ };

arch/arm/boot/dts/bcm2835-rpi.dtsi

@@ -16,6 +16,13 @@
  };
  };
 
+ customer_otp: otp {
+ compatible = "raspberrypi,bcm2835-customer-otp";
+ firmware = <&firmware>;
+ #address-cells = <1>;
+ #size-cells = <1>;
+ };
+
  soc {
  firmware: firmware {
  compatible = "raspberrypi,bcm2835-firmware";

drivers/nvmem/Kconfig

@@ -111,4 +111,14 @@ config MESON_EFUSE
  This driver can also be built as a module. If so, the module
  will be called nvmem_meson_efuse.
 
+config NVMEM_RASPBERRYPI_OTP
+ tristate "Raspberry Pi Customer OTP support"
+ depends on ARCH_BCM2835 || COMPILE_TEST
+ depends on RASPBERRYPI_FIRMWARE
+ help
+ This is a driver for access to the Customer OTP on the Raspberry Pi.
+
+ This driver can also be built as a module. If so, the module
+ will be called nvmem-raspberrypi-otp.
+
 endif

drivers/nvmem/Makefile

@@ -24,3 +24,5 @@ obj-$(CONFIG_NVMEM_VF610_OCOTP) += nvmem-vf610-ocotp.o
 nvmem-vf610-ocotp-y := vf610-ocotp.o
 obj-$(CONFIG_MESON_EFUSE) += nvmem_meson_efuse.o
 nvmem_meson_efuse-y := meson-efuse.o
+obj-$(CONFIG_NVMEM_RASPBERRYPI_OTP) += nvmem-raspberrypi-otp.o
+nvmem-raspberrypi-otp-y := raspberrypi-otp.o

drivers/nvmem/raspberrypi-otp.c

@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Raspberry Pi Customer OTP driver
+ *
+ * Copyright (C) 2018 Stefan Wahren <stefan.wahren@i2se.com>
+ */
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#define CUSTOMER_CELLS 8
+
+struct rpi_otp {
+ struct nvmem_device *nvmem;
+ struct rpi_firmware *fw;
+};
+
+/*
+ * Packet definition used by RPI_FIRMWARE_GET_CUSTOMER_OTP
+ */
+struct rpi_customer_otp_packet {
+ u32 index;
+ u32 length;
+ u32 cells[CUSTOMER_CELLS];
+};
+
+static int rpi_otp_read(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct rpi_customer_otp_packet packet;
+ struct rpi_otp *otp = context;
+ u32 *buf = val;
+ int ret;
+
+ packet.index = 0;
+ packet.length = CUSTOMER_CELLS;
+ memset(packet.cells, 0xff, sizeof(packet.cells));
+
+ ret = rpi_firmware_property(otp->fw, RPI_FIRMWARE_GET_CUSTOMER_OTP,
+ &packet, sizeof(packet));
+
+ if (ret)
+ return ret;
+
+ /* Request rejected by firmware */
+ if (packet.index)
+ return -EIO;
+
+ while (bytes) {
+ if ((offset / 4) < sizeof(packet.cells))
+ *buf = packet.cells[offset / 4];
+ else
+ *buf = 0;
+
+ buf++;
+ bytes -= 4;
+ offset += 4;
+ }
+
+ return 0;
+}
+
+static struct nvmem_config ocotp_config = {
+ .name = "rpi-customer-otp",
+ .size = CUSTOMER_CELLS * 4,
+ .stride = 4,
+ .word_size = 4,
+ .reg_read = rpi_otp_read,
+};
+
+static int rpi_otp_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ const struct of_device_id *match;
+ struct device_node *fw_np;
+ struct rpi_otp *otp;
+
+ match = of_match_device(dev->driver->of_match_table, dev);
+ if (!match)
+ return -EINVAL;
+
+ otp = devm_kzalloc(dev, sizeof(*otp), GFP_KERNEL);
+ if (!otp)
+ return -ENOMEM;
+
+ fw_np = of_parse_phandle(pdev->dev.of_node, "firmware", 0);
+ if (!fw_np) {
+ dev_err(&pdev->dev, "no firmware node\n");
+ return -ENODEV;
+ }
+
+ otp->fw = rpi_firmware_get(fw_np);
+ of_node_put(fw_np);
+ if (!otp->fw)
+ return -EPROBE_DEFER;
+
+ ocotp_config.priv = otp;
+ ocotp_config.dev = dev;
+ otp->nvmem = nvmem_register(&ocotp_config);
+ if (IS_ERR(otp->nvmem))
+ return PTR_ERR(otp->nvmem);
+
+ platform_set_drvdata(pdev, otp);
+
+ return 0;
+}
+
+static int rpi_otp_remove(struct platform_device *pdev)
+{
+ struct rpi_otp *otp = platform_get_drvdata(pdev);
+
+ return nvmem_unregister(otp->nvmem);
+}
+
+static const struct of_device_id rpi_otp_of_match[] = {
+ { .compatible = "raspberrypi,bcm2835-customer-otp", },
+ { /* sentinel */},
+};
+MODULE_DEVICE_TABLE(of, rpi_otp_of_match);
+
+static struct platform_driver rpi_otp_driver = {
+ .probe = rpi_otp_probe,
+ .remove = rpi_otp_remove,
+ .driver = {
+ .name = "rpi-customer-otp",
+ .of_match_table = rpi_otp_of_match,
+ },
+};
+
+module_platform_driver(rpi_otp_driver);
+MODULE_AUTHOR("Stefan Wahren <stefan.wahren@i2se.com>");
+MODULE_DESCRIPTION("Raspberry Pi Customer OTP driver");
+MODULE_LICENSE("GPL v2");