Re: [PATCH v6 2/4] power: reset: add reboot mode driver

Krzysztof Kozlowski
2016-03-24T02:50:55Z

Cool work! Few comments below.

On Tue, Mar 22, 2016 at 8:37 PM, Andy Yan <andy.yan@rock-chips.com> wrote:
> This driver parse the reboot commands like "reboot loader"
> and "reboot recovery" to get a boot mode described in the
> device tree , then call the write interfae to store the boot
> mode in some place like special register or sram , which can
> be read by the bootloader after system reboot, then the bootloader
> can take different action according to the mode stored.
>
> This is commonly used on Android based devices, in order to
> reboot the device into fastboot or recovery mode.
>
> Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
> Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>
> Tested-by: John Stultz <john.stultz@linaro.org>
> Acked-by: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
>
> ---
>
> Changes in v6: None
> Changes in v5:
> - use two blank space under help in Kconfig
> - use unsigned int instead of int for member magic in struct mode_info
>
> Changes in v4:
> - make this driver depends on OF to avoid kbuild test error
>
> Changes in v3:
> - scan multi properities
> - add mask value for some platform which only use some bits of the register
> to store boot mode magic value
>
> Changes in v2:
> - move to dir drivers/power/reset/
> - make syscon-reboot-mode a generic driver
>
> Changes in v1:
> - fix the embarrassed compile warning
> - correct the maskrom magic number
> - check for the normal reboot
>
> drivers/power/reset/Kconfig | 13 ++++
> drivers/power/reset/Makefile | 2 +
> drivers/power/reset/reboot-mode.c | 106 +++++++++++++++++++++++++++++++
> drivers/power/reset/reboot-mode.h | 6 ++
> drivers/power/reset/syscon-reboot-mode.c | 65 +++++++++++++++++++
> 5 files changed, 192 insertions(+)
> create mode 100644 drivers/power/reset/reboot-mode.c
> create mode 100644 drivers/power/reset/reboot-mode.h
> create mode 100644 drivers/power/reset/syscon-reboot-mode.c
>
> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> index 1131cf7..cf50630 100644
> --- a/drivers/power/reset/Kconfig
> +++ b/drivers/power/reset/Kconfig
> @@ -173,5 +173,18 @@ config POWER_RESET_ZX
> help
> Reboot support for ZTE SoCs.
>
> +config REBOOT_MODE
> + tristate
> +
> +config SYSCON_REBOOT_MODE
> + bool "Generic SYSCON regmap reboot mode driver"
> + depends on OF
> + select REBOOT_MODE
> + help
> + Say y here will enable reboot mode driver. This will
> + get reboot mode arguments and store it in SYSCON mapped
> + register, then the bootloader can read it to take different
> + action according to the mode.
> +
> endif
>
> diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
> index 096fa67..a63865b 100644
> --- a/drivers/power/reset/Makefile
> +++ b/drivers/power/reset/Makefile
> @@ -20,3 +20,5 @@ obj-$(CONFIG_POWER_RESET_SYSCON) += syscon-reboot.o
> obj-$(CONFIG_POWER_RESET_SYSCON_POWEROFF) += syscon-poweroff.o
> obj-$(CONFIG_POWER_RESET_RMOBILE) += rmobile-reset.o
> obj-$(CONFIG_POWER_RESET_ZX) += zx-reboot.o
> +obj-$(CONFIG_REBOOT_MODE) += reboot-mode.o
> +obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o
> diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
> new file mode 100644
> index 0000000..9aa7b80
> --- /dev/null
> +++ b/drivers/power/reset/reboot-mode.c
> @@ -0,0 +1,106 @@
> +/*
> + * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/reboot.h>
> +#include "reboot-mode.h"
> +
> +#define PREFIX "mode-"
> +
> +struct mode_info {
> + char mode[32];
> + unsigned int magic;
> + struct list_head list;
> +};
> +
> +struct reboot_mode_driver {
> + struct list_head head;
> + int (*write)(int magic);
> + struct notifier_block reboot_notifier;
> +};
> +
> +static int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
> + const char *cmd)
> +{
> + const char *normal = "normal";
> + int magic = 0;
> + struct mode_info *info;
> +
> + if (!cmd)
> + cmd = normal;
> +
> + list_for_each_entry(info, &reboot->head, list) {
> + if (!strcmp(info->mode, cmd)) {
> + magic = info->magic;
> + break;
> + }
> + }
> +
> + return magic;

In absence of 'normal' mode (it is not described as required property)
the magic will be '0'. It would be nice to document that in bindings.
Imagine someone forgets about this and will wonder why 0x0 is written
to his precious register on normal reboot...

It would be nice to document that 'mode-normal' has a special
(hard-coded) meaning.

> +}
> +
> +static int reboot_mode_notify(struct notifier_block *this,
> + unsigned long mode, void *cmd)
> +{
> + struct reboot_mode_driver *reboot;
> + int magic;
> +
> + reboot = container_of(this, struct reboot_mode_driver, reboot_notifier);
> + magic = get_reboot_mode_magic(reboot, cmd);
> + if (magic)
> + reboot->write(magic);
> +
> + return NOTIFY_DONE;
> +}
> +
> +int reboot_mode_register(struct device *dev, int (*write)(int))
> +{
> + struct reboot_mode_driver *reboot;
> + struct mode_info *info;
> + struct property *prop;
> + size_t len = strlen(PREFIX);
> + int ret;
> +
> + reboot = devm_kzalloc(dev, sizeof(*reboot), GFP_KERNEL);
> + if (!reboot)
> + return -ENOMEM;
> +
> + reboot->write = write;
> + INIT_LIST_HEAD(&reboot->head);
> + for_each_property_of_node(dev->of_node, prop) {
> + if (len > strlen(prop->name) || strncmp(prop->name, PREFIX, len))
> + continue;

New line please for readability.

> + info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
> + if (!info)
> + return -ENOMEM;

Ditto.

> + strcpy(info->mode, prop->name + len);

Ehm, and how do you protect that name of mode is shorter than 32 characters?

> + if (of_property_read_u32(dev->of_node, prop->name, &info->magic)) {
> + dev_err(dev, "reboot mode %s without magic number\n",
> + info->mode);
> + devm_kfree(dev, info);
> + continue;
> + }
> + list_add_tail(&info->list, &reboot->head);
> + }
> + reboot->reboot_notifier.notifier_call = reboot_mode_notify;
> + ret = register_reboot_notifier(&reboot->reboot_notifier);
> + if (ret)
> + dev_err(dev, "can't register reboot notifier\n");
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(reboot_mode_register);
> +
> +MODULE_AUTHOR("Andy Yan <andy.yan@rock-chips.com");
> +MODULE_DESCRIPTION("System reboot mode driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/power/reset/reboot-mode.h b/drivers/power/reset/reboot-mode.h
> new file mode 100644
> index 0000000..44ed34f
> --- /dev/null
> +++ b/drivers/power/reset/reboot-mode.h
> @@ -0,0 +1,6 @@
> +#ifndef __REBOOT_MODE_H__
> +#define __REBOOT_MODE_H__
> +
> +int reboot_mode_register(struct device *dev, int (*write)(int));

Documentation would be appreciated. Although it is local header but
you decoupled them and you are exporting the function.

> +
> +#endif
> diff --git a/drivers/power/reset/syscon-reboot-mode.c b/drivers/power/reset/syscon-reboot-mode.c
> new file mode 100644
> index 0000000..d1521d8
> --- /dev/null
> +++ b/drivers/power/reset/syscon-reboot-mode.c
> @@ -0,0 +1,65 @@
> +/*
> + * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>

I don't see the need of of_address or am I missing something?

> +#include <linux/platform_device.h>
> +#include <linux/reboot.h>
> +#include <linux/regmap.h>
> +#include <linux/mfd/syscon.h>
> +#include "reboot-mode.h"
> +
> +static struct regmap *map;
> +static u32 offset;
> +static u32 mask = 0xffffffff;

Why this cannot be part of state container? I suppose usually there
will be only one reboot mode handler, but:
1. It is always nice to make things self-contained, so code could be
easily used in different contexts. Depending on static variables
prevents that.
2. How do you protect against double binding (two reboot mode device
nodes in DT)? The second binding (put by mistake... or whatever
reason) will overwrite data used by previous device.

> +
> +static int syscon_reboot_mode_write(int magic)
> +{
> + regmap_update_bits(map, offset, mask, magic);
> +
> + return 0;

Why ignoring return value of regmap_update_bits?

> +}
> +
> +static int syscon_reboot_mode_probe(struct platform_device *pdev)
> +{
> + int ret;
> +
> + map = syscon_node_to_regmap(pdev->dev.parent->of_node);
> + if (IS_ERR(map))
> + return PTR_ERR(map);

Empty line for readability.

> + if (of_property_read_u32(pdev->dev.of_node, "offset", &offset))
> + return -EINVAL;

Empty line for readability.

Best regards,
Krzysztof