linux-kernel - Re: [PATCH v4 3/3] nvmem: Add Apple eFuse driver

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Message-ID: <92e94b98-847d-7d3f-4063-96d2d01eff6e@linaro.org>
Date:   Mon, 11 Apr 2022 10:41:06 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Sven Peter <sven@...npeter.dev>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowsk <krzysztof.kozlowski@...onical.com>,
        Joey Gouly <joey.gouly@....com>,
        Hector Martin <marcan@...can.st>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Mark Kettenis <kettenis@...nbsd.org>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] nvmem: Add Apple eFuse driver



On 10/04/2022 14:54, Sven Peter wrote:
> 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@...npeter.dev>


Applied all 3,

thanks,
--srini


> ---
> v3 -> v4:
>    - rebased on 5.18-rc1 and split off MAINTAINER changes as requested
>      by Srinivas Kandagatla
> v2 -> v3:
>    - removed .owner = THIS_MODULE again since it's already done by the
>      core as pointed out by Krzysztof Kozlowski
> v1 -> v2:
>    - fixed sparse warning about __iomem by introducing
>      struct apple_efuses_priv as done in other nvmem drivers
>    - make sure the driver actually works as a module by
>      setting .owner to THIS_MODULE and adding MODULE_DEVICE_TABLE
>      pointed out by Joey Gouly
> 
>   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
> 
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index 555aa77a574d..6283e09cc1e9 100644
> --- 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 891958e29d25..00e136a0a123 100644
> --- 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
> index 000000000000..9b7c87102104
> --- /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@...npeter.dev>");
> +MODULE_LICENSE("GPL");