Re: [PATCH v2 4/6] nvmem: add support for the Khadas MCU Programmable User Memory
From: Srinivas Kandagatla
Date: Wed May 13 2020 - 06:34:20 EST
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@xxxxxxxxxxxx>
---
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@xxxxxxxxxxxx>
+ */
+
+#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@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Khadas MCU User MEM driver");
+MODULE_LICENSE("GPL v2");