Re: [PATCH] power: reset: make reboot-mode user selectable

[Sebastian Reichel <sre@kernel.org>]

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Hi Arnd and Nandor,

On Mon, Aug 05, 2019 at 09:57:15AM +0200, Arnd Bergmann wrote:
> Nandor Han points out that there might be drivers that can use
> the reboot-mode interfaces but might also be usable on configurations
> without device tree.
> 
> Move the 'depends on OF' dependency into CONFIG_REBOOT_MODE since
> that is the only thing that truely has a compile-time dependency
> on CONFIG_OF, and make it user visible to make it possible to
> disable it.
> 
> The drivers that used to 'select REBOOT_MODE' of course now have to
> use 'depends on REBOOT_MODE instead'. With this, we can soften the
> dependency and allow compile-testing the three front-end drivers
> on non-OF platforms.
> 
> Note: anyone who was using a reboot mode driver in their kernel
> configuration now has to enable CONFIG_REBOOT_MODE as well.
> 
> Suggested-by: Nandor Han <nandor.han@vaisala.com>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> Nandor, this is so far untested, could you make sure this
> works in all configurations and forward it along with the
> bugfix?
> 
> Sebastian, I'm not convinced this is a good idea, just sending
> it as Nandor requested. Please decide for yourself.
> ---

(Sorry for late reply)

This patch does not look good to me. Better patch would be to
allow compiling CONFIG_REBOOT_MODE without CONFIG_OF. Obviously
the configuration would not be useful for anything except compile
testing, but that is also true for this patch.

Making the small OF dependent section in reboot_mode_register()
would be a smaller patch with bigger test coverage, without
breakng existing configurations.

-- Sebastian

>  arch/arm/configs/davinci_all_defconfig |  1 +
>  arch/arm64/configs/defconfig           |  1 +
>  drivers/power/reset/Kconfig            | 22 +++++++++++++---------
>  include/linux/reboot-mode.h            | 20 ++++++++++++++++++++
>  4 files changed, 35 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm/configs/davinci_all_defconfig b/arch/arm/configs/davinci_all_defconfig
> index b34970ce6b31..ebf506c01899 100644
> --- a/arch/arm/configs/davinci_all_defconfig
> +++ b/arch/arm/configs/davinci_all_defconfig
> @@ -139,6 +139,7 @@ CONFIG_GPIO_PCA953X_IRQ=y
>  CONFIG_RESET_CONTROLLER=y
>  CONFIG_POWER_RESET=y
>  CONFIG_POWER_RESET_GPIO=y
> +CONFIG_REBOOT_MODE=m
>  CONFIG_SYSCON_REBOOT_MODE=m
>  CONFIG_BATTERY_LEGO_EV3=m
>  CONFIG_WATCHDOG=y
> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
> index 0e58ef02880c..bb7d7bec1413 100644
> --- a/arch/arm64/configs/defconfig
> +++ b/arch/arm64/configs/defconfig
> @@ -419,6 +419,7 @@ CONFIG_ROCKCHIP_IODOMAIN=y
>  CONFIG_POWER_RESET_MSM=y
>  CONFIG_POWER_RESET_XGENE=y
>  CONFIG_POWER_RESET_SYSCON=y
> +CONFIG_REBOOT_MODE=y
>  CONFIG_SYSCON_REBOOT_MODE=y
>  CONFIG_BATTERY_SBS=m
>  CONFIG_BATTERY_BQ27XXX=y
> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> index a564237278ff..997323d443f5 100644
> --- a/drivers/power/reset/Kconfig
> +++ b/drivers/power/reset/Kconfig
> @@ -9,6 +9,13 @@ menuconfig POWER_RESET
>  
>  if POWER_RESET
>  
> +config REBOOT_MODE
> +	tristate "Pass reboot-mode to firmware"
> +	depends on OF
> +	help
> +	  Some drivers allow setting the reboot mode through a platform
> +	  interface that the boot firmware can read.
> +
>  config POWER_RESET_AS3722
>  	bool "ams AS3722 power-off driver"
>  	depends on MFD_AS3722
> @@ -107,9 +114,9 @@ config POWER_RESET_MSM
>  
>  config POWER_RESET_QCOM_PON
>  	tristate "Qualcomm power-on driver"
> -	depends on ARCH_QCOM
> +	depends on ARCH_QCOM || COMPILE_TEST
>  	depends on MFD_SPMI_PMIC
> -	select REBOOT_MODE
> +	depends on REBOOT_MODE || !REBOOT_MODE
>  	help
>  	  Power On support for Qualcomm boards.
>  	  If you have a Qualcomm platform and need support for
> @@ -223,14 +230,11 @@ config POWER_RESET_ZX
>  	help
>  	  Reboot support for ZTE SoCs.
>  
> -config REBOOT_MODE
> -	tristate
> -
>  config SYSCON_REBOOT_MODE
>  	tristate "Generic SYSCON regmap reboot mode driver"
> -	depends on OF
> +	depends on OF || COMPILE_TEST
>  	depends on MFD_SYSCON
> -	select REBOOT_MODE
> +	depends on REBOOT_MODE || !REBOOT_MODE
>  	help
>  	  Say y here will enable reboot mode driver. This will
>  	  get reboot mode arguments and store it in SYSCON mapped
> @@ -248,8 +252,8 @@ config POWER_RESET_SC27XX
>  
>  config NVMEM_REBOOT_MODE
>  	tristate "Generic NVMEM reboot mode driver"
> -	depends on OF
> -	select REBOOT_MODE
> +	depends on OF || COMPILE_TEST
> +	depends on REBOOT_MODE || !REBOOT_MODE
>  	help
>  	  Say y here will enable reboot mode driver. This will
>  	  get reboot mode arguments and store it in a NVMEM cell,
> diff --git a/include/linux/reboot-mode.h b/include/linux/reboot-mode.h
> index 4a2abb38d1d6..bd002060e3d0 100644
> --- a/include/linux/reboot-mode.h
> +++ b/include/linux/reboot-mode.h
> @@ -9,11 +9,31 @@ struct reboot_mode_driver {
>  	struct notifier_block reboot_notifier;
>  };
>  
> +#if IS_ENABLED(CONFIG_REBOOT_MODE)
>  int reboot_mode_register(struct reboot_mode_driver *reboot);
>  int reboot_mode_unregister(struct reboot_mode_driver *reboot);
>  int devm_reboot_mode_register(struct device *dev,
>  			      struct reboot_mode_driver *reboot);
>  void devm_reboot_mode_unregister(struct device *dev,
>  				 struct reboot_mode_driver *reboot);
> +#else
> +static inline int reboot_mode_register(struct reboot_mode_driver *reboot)
> +{
> +	return 0;
> +}
> +static inline int reboot_mode_unregister(struct reboot_mode_driver *reboot)
> +{
> +	return 0;
> +}
> +static inline int devm_reboot_mode_register(struct device *dev,
> +			      struct reboot_mode_driver *reboot)
> +{
> +	return 0;
> +}
> +static inline void devm_reboot_mode_unregister(struct device *dev,
> +				 struct reboot_mode_driver *reboot)
> +{
> +}
> +#endif
>  
>  #endif
> -- 
> 2.20.0
> 

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