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Date: Wed, 13 May 2020 11:34:13 +0100
From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To: Neil Armstrong <narmstrong@...libre.com>
Cc: linux-amlogic@...ts.infradead.org, linux-pm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/6] nvmem: add support for the Khadas MCU Programmable
User Memory
On 12/05/2020 14:26, Neil Armstrong wrote:
> The new Khadas VIM2, VIM3 and Edge boards embeds an on-board microcontroller
> offering a 56bytes User Programmable NVMEM array.
>
> This array needs a password to be writable, thus a password sysfs file
> has been added on the device node to unlock the NVMEM.
Is this one time programmable? Or does it need to be unlocked for every
read/write?
How can you make sure that the memory is unlocked before making attempt
to read/write?
>
> The default 6bytes password id: "Khadas"
>
> This implements the user NVMEM devices as cell of the Khadas MCU MFD driver.
>
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
> drivers/nvmem/Kconfig | 8 ++
> drivers/nvmem/Makefile | 2 +
> drivers/nvmem/khadas-mcu-user-mem.c | 128 ++++++++++++++++++++++++++++
> 3 files changed, 138 insertions(+)
> create mode 100644 drivers/nvmem/khadas-mcu-user-mem.c
>
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index d7b7f6d688e7..92cd4f6aa931 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -67,6 +67,14 @@ config JZ4780_EFUSE
> To compile this driver as a module, choose M here: the module
> will be called nvmem_jz4780_efuse.
>
> +config NVMEM_KHADAS_MCU_USER_MEM
> + tristate "Khadas MCU User programmable memory support"
> + depends on MFD_KHADAS_MCU
> + depends on REGMAP
> + help
> + This is a driver for the MCU User programmable memory
> + available on the Khadas VIM and Edge boards.
> +
> config NVMEM_LPC18XX_EEPROM
> tristate "NXP LPC18XX EEPROM Memory Support"
> depends on ARCH_LPC18XX || COMPILE_TEST
> diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> index a7c377218341..0516a309542d 100644
> --- a/drivers/nvmem/Makefile
> +++ b/drivers/nvmem/Makefile
> @@ -17,6 +17,8 @@ obj-$(CONFIG_NVMEM_IMX_OCOTP_SCU) += nvmem-imx-ocotp-scu.o
> nvmem-imx-ocotp-scu-y := imx-ocotp-scu.o
> obj-$(CONFIG_JZ4780_EFUSE) += nvmem_jz4780_efuse.o
> nvmem_jz4780_efuse-y := jz4780-efuse.o
> +obj-$(CONFIG_NVMEM_KHADAS_MCU_USER_MEM) += nvmem-khadas-mcu-user-mem.o
> +nvmem-khadas-mcu-user-mem-y := khadas-mcu-user-mem.o
> obj-$(CONFIG_NVMEM_LPC18XX_EEPROM) += nvmem_lpc18xx_eeprom.o
> nvmem_lpc18xx_eeprom-y := lpc18xx_eeprom.o
> obj-$(CONFIG_NVMEM_LPC18XX_OTP) += nvmem_lpc18xx_otp.o
> diff --git a/drivers/nvmem/khadas-mcu-user-mem.c b/drivers/nvmem/khadas-mcu-user-mem.c
> new file mode 100644
> index 000000000000..a1d5ae9a030c
> --- /dev/null
> +++ b/drivers/nvmem/khadas-mcu-user-mem.c
> @@ -0,0 +1,128 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for Khadas MCU User programmable Memory
> + *
> + * Copyright (C) 2020 BayLibre SAS
> + * Author(s): Neil Armstrong <narmstrong@...libre.com>
> + */
> +
> +#include <linux/clk.h>
Why do we need this header?
> +#include <linux/module.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/mfd/khadas-mcu.h>
> +#include <linux/regmap.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +static int khadas_mcu_user_mem_read(void *context, unsigned int offset,
> + void *val, size_t bytes)
> +{
> + struct khadas_mcu *khadas_mcu = context;
> +
> + return regmap_bulk_read(khadas_mcu->map,
> + KHADAS_MCU_USER_DATA_0_REG + offset,
> + val, bytes);
> +}
> +
> +static int khadas_mcu_user_mem_write(void *context, unsigned int offset,
> + void *val, size_t bytes)
> +{
> + struct khadas_mcu *khadas_mcu = context;
> +
> + return regmap_bulk_write(khadas_mcu->map,
> + KHADAS_MCU_USER_DATA_0_REG + offset,
> + val, bytes);
> +}
> +
> +static ssize_t password_store(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct khadas_mcu *khadas_mcu = dev_get_drvdata(dev);
> + int i, ret;
> +
> + if (count < 6)
> + return -EINVAL;
Possibly this magic 6 value needs proper define. An additional check
here for > 6 would be better as well.
> +
> + ret = regmap_write(khadas_mcu->map, KHADAS_MCU_PASSWD_START_REG, 1);
> + if (ret)
> + return ret;
> +
> + for (i = 0 ; i < 6 ; ++i) {
> + ret = regmap_write(khadas_mcu->map,
> + KHADAS_MCU_CHECK_USER_PASSWD_REG,
> + buf[i]);
> + if (ret)
> + goto out;
> + }
> +
> + ret = regmap_write(khadas_mcu->map, KHADAS_MCU_PASSWD_START_REG, 0);
> + if (ret)
> + return ret;
> +
> + return count;
> +out:
> + regmap_write(khadas_mcu->map, KHADAS_MCU_PASSWD_START_REG, 0);
> +
> + return ret;
> +}
> +
> +static DEVICE_ATTR_WO(password);
> +
> +static struct attribute *khadas_mcu_user_mem_sysfs_attributes[] = {
> + &dev_attr_password.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group khadas_mcu_user_mem_sysfs_attr_group = {
> + .attrs = khadas_mcu_user_mem_sysfs_attributes,
> +};
> +
> +static int khadas_mcu_user_mem_probe(struct platform_device *pdev)
> +{
> + struct khadas_mcu *khadas_mcu = dev_get_drvdata(pdev->dev.parent);
You could probably get away with dependency of this structure and the
header itself by directly getting hold of regmap from parent device.
> + struct device *dev = &pdev->dev;
> + struct nvmem_device *nvmem;
> + struct nvmem_config *econfig;
> +
> + econfig = devm_kzalloc(dev, sizeof(*econfig), GFP_KERNEL);
> + if (!econfig)
> + return -ENOMEM;
> +
> + econfig->dev = pdev->dev.parent;
> + econfig->name = dev_name(pdev->dev.parent);
> + econfig->stride = 1;
> + econfig->word_size = 1;
> + econfig->reg_read = khadas_mcu_user_mem_read;
> + econfig->reg_write = khadas_mcu_user_mem_write;
> + econfig->size = 56;
define 56 to make it more readable!
> + econfig->priv = khadas_mcu;
> +
> + platform_set_drvdata(pdev, khadas_mcu);
> +
> + nvmem = devm_nvmem_register(&pdev->dev, econfig);
> + if (IS_ERR(nvmem))
> + return PTR_ERR(nvmem);
> +
> + return sysfs_create_group(&pdev->dev.kobj,
> + &khadas_mcu_user_mem_sysfs_attr_group);
> +}
> +
> +static const struct platform_device_id khadas_mcu_user_mem_id_table[] = {
> + { .name = "khadas-mcu-user-mem", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(platform, khadas_mcu_user_mem_id_table);
> +
> +static struct platform_driver khadas_mcu_user_mem_driver = {
> + .probe = khadas_mcu_user_mem_probe,
> + .driver = {
> + .name = "khadas-mcu-user-mem",
> + },
> + .id_table = khadas_mcu_user_mem_id_table,
> +};
> +
> +module_platform_driver(khadas_mcu_user_mem_driver);
> +
> +MODULE_AUTHOR("Neil Armstrong <narmstrong@...libre.com>");
> +MODULE_DESCRIPTION("Khadas MCU User MEM driver");
> +MODULE_LICENSE("GPL v2");
>
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