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>

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 555aa77..6283e09 100644 (file)
--- 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

diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 891958e..00e136a 100644 (file)
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -65,3 +65,5 @@ obj-$(CONFIG_NVMEM_LAYERSCAPE_SFP)    += nvmem-layerscape-sfp.o
 nvmem-layerscape-sfp-y         := layerscape-sfp.o
 obj-$(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

diff --git a/drivers/nvmem/apple-efuses.c b/drivers/nvmem/apple-efuses.c
new file mode 100644 (file)
index 0000000..9b7c871
--- /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");