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

[Andy Yan]

Hi Krzystof:

On 2016å03æ24æ 10:50, Krzysztof Kozlowski wrote:
> Cool work! Few comments below.
>
>
> On Tue, Mar 22, 2016 at 8:37 PM, Andy Yan <andy.yan@xxxxxxxxxxxxxx> 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@xxxxxxxxx>
> > Reviewed-by: Moritz Fischer <moritz.fischer@xxxxxxxxx>
> > Tested-by: John Stultz <john.stultz@xxxxxxxxxx>
> > Acked-by: John Stultz <john.stultz@xxxxxxxxxx>
> > Signed-off-by: Andy Yan <andy.yan@xxxxxxxxxxxxxx>
> >
> > ---
> >
> > 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...

    If the magic value is '0', we won't touch the register, please see 
reboot_mode_notify bellow.
> 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.

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

    Okay
> > +               strcpy(info->mode, prop->name + len);
> Ehm, and how do you protect that name of mode is shorter than 32 characters?

    How about info->mode = prop->name + len ?
> > +               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@xxxxxxxxxxxxxx");
> > +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.

    I think I should remove the EXPORT_SYMBOL_GPL.
> > +
> > +#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?

    Yes, it useless, I will remove it.
> > +#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.

    Okay, I will make this self-contained.
> > +
> > +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?

    Okay, I will check it.
> > +}
> > +
> > +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.
    ok
> > +       if (of_property_read_u32(pdev->dev.of_node, "offset", &offset))
> > +               return -EINVAL;
> Empty line for readability.
    ok
> Best regards,
> Krzysztof