Messages in this thread | | | Subject | Re: [PATCH v2 4/6] nvmem: add support for the Khadas MCU Programmable User Memory | From | Neil Armstrong <> | Date | Tue, 2 Jun 2020 10:29:16 +0200 |
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On 15/05/2020 12:55, Srinivas Kandagatla wrote: > > > On 13/05/2020 13:33, Neil Armstrong wrote: >> On 13/05/2020 12:34, Srinivas Kandagatla wrote: >>> >>> >>> 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? >> >> It can be rewritten, and needs the password to read & write. >> >>> >>> How can you make sure that the memory is unlocked before making attempt to read/write? >> >> The only way to know it's unlock is reading back the password when unlocked. > > > Current code has no such checks for every read/write? > and looks very disconnected w.r.t to password and read/writes. > > If user attempts to read/write he will not be aware that he should program the password first! > > Also if the password is static or un-changed then why not just statically program this from the driver rather than providing sysfs file?
The passworsd can be changed, how should this be taken in account ?
> > I dont see how kernel nvmem read/write interface can make sure that memory is unlocked?
Not sure how to be sure, if locked all the user memory and password is read as 0xff
> > Who is the real consumer for this provider?
well, it's more user-space, indeed without the in-kernel password unlock, kernel won't be able to make great use of the data.
I'll drop for next serie until we have a clearer view.
Neil
> > --srini > > >> >>> >>>> >>>> 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@baylibre.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@baylibre.com> >>>> + */ >>>> + >>>> +#include <linux/clk.h> >>> >>> Why do we need this header? >> >> Will drop >> >>> >>>> +#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. >> >> Ok >> >>> >>>> + >>>> + 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. >> >> Ok >> >>> >>> >>>> + 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! >> >> Ok >> >>> >>>> + 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@baylibre.com>"); >>>> +MODULE_DESCRIPTION("Khadas MCU User MEM driver"); >>>> +MODULE_LICENSE("GPL v2"); >>>> >> >> Thanks for the review. >> >> Neil >>
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