From b6b7ef932ae838209254f016ecf8862d716a5ced Mon Sep 17 00:00:00 2001
From: Sven Peter <sven@svenpeter.dev>
Date: Fri, 29 Apr 2022 17:26:50 +0100
Subject: [PATCH] nvmem: Add Apple eFuse driver
Apple SoCs contain eFuses used to store factory-programmed data such
as calibration values for the PCIe or the Type-C PHY. They are organized
as 32bit values exposed as MMIO.
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20220429162701.2222-6-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/nvmem/Kconfig | 12 ++++++
drivers/nvmem/Makefile | 2 +
drivers/nvmem/apple-efuses.c | 80 ++++++++++++++++++++++++++++++++++++
3 files changed, 94 insertions(+)
create mode 100644 drivers/nvmem/apple-efuses.c
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -324,4 +324,16 @@ config NVMEM_SUNPLUS_OCOTP
This driver can also be built as a module. If so, the module
will be called nvmem-sunplus-ocotp.
+config NVMEM_APPLE_EFUSES
+ tristate "Apple eFuse support"
+ depends on ARCH_APPLE || COMPILE_TEST
+ default ARCH_APPLE
+ help
+ Say y here to enable support for reading eFuses on Apple SoCs
+ such as the M1. These are e.g. used to store factory programmed
+ calibration data required for the PCIe or the USB-C PHY.
+
+ This driver can also be built as a module. If so, the module will
+ be called nvmem-apple-efuses.
+
endif
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -65,3 +65,5 @@ obj-$(CONFIG_NVMEM_LAYERSCAPE_SFP) += nv
nvmem-layerscape-sfp-y := layerscape-sfp.o
obj-$(CONFIG_NVMEM_SUNPLUS_OCOTP) += nvmem_sunplus_ocotp.o
nvmem_sunplus_ocotp-y := sunplus-ocotp.o
+obj-$(CONFIG_NVMEM_APPLE_EFUSES) += nvmem-apple-efuses.o
+nvmem-apple-efuses-y := apple-efuses.o
--- /dev/null
+++ b/drivers/nvmem/apple-efuses.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Apple SoC eFuse driver
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#include <linux/io.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+
+struct apple_efuses_priv {
+ void __iomem *fuses;
+};
+
+static int apple_efuses_read(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct apple_efuses_priv *priv = context;
+ u32 *dst = val;
+
+ while (bytes >= sizeof(u32)) {
+ *dst++ = readl_relaxed(priv->fuses + offset);
+ bytes -= sizeof(u32);
+ offset += sizeof(u32);
+ }
+
+ return 0;
+}
+
+static int apple_efuses_probe(struct platform_device *pdev)
+{
+ struct apple_efuses_priv *priv;
+ struct resource *res;
+ struct nvmem_config config = {
+ .dev = &pdev->dev,
+ .read_only = true,
+ .reg_read = apple_efuses_read,
+ .stride = sizeof(u32),
+ .word_size = sizeof(u32),
+ .name = "apple_efuses_nvmem",
+ .id = NVMEM_DEVID_AUTO,
+ .root_only = true,
+ };
+
+ priv = devm_kzalloc(config.dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->fuses = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+ if (IS_ERR(priv->fuses))
+ return PTR_ERR(priv->fuses);
+
+ config.priv = priv;
+ config.size = resource_size(res);
+
+ return PTR_ERR_OR_ZERO(devm_nvmem_register(config.dev, &config));
+}
+
+static const struct of_device_id apple_efuses_of_match[] = {
+ { .compatible = "apple,efuses", },
+ {}
+};
+
+MODULE_DEVICE_TABLE(of, apple_efuses_of_match);
+
+static struct platform_driver apple_efuses_driver = {
+ .driver = {
+ .name = "apple_efuses",
+ .of_match_table = apple_efuses_of_match,
+ },
+ .probe = apple_efuses_probe,
+};
+
+module_platform_driver(apple_efuses_driver);
+
+MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>");
+MODULE_LICENSE("GPL");