linux-kernel - Re: [RFC v1] opp: add config option for debug

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Date:   Wed, 4 May 2022 20:24:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Frank Wunderlich <linux@...web.de>
Cc:     linux-pm@...r.kernel.org,
        Frank Wunderlich <frank-w@...lic-files.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC v1] opp: add config option for debug

On Wed, May 04, 2022 at 07:48:23PM +0200, Frank Wunderlich wrote:
> From: Frank Wunderlich <frank-w@...lic-files.de>
> 
> Currently OPP debug is enabled by DEBUG_DRIVER option. This is generic
> driver debug and opp floods serial console. This is annoying if opp is
> not needed so give it an additional config-key.
> 
> Signed-off-by: Frank Wunderlich <frank-w@...lic-files.de>
> ---
>  drivers/base/Kconfig | 1 +
>  drivers/opp/Kconfig  | 7 +++++++
>  drivers/opp/Makefile | 2 +-
>  3 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 6f04b831a5c0..8ae826c95d5f 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -130,6 +130,7 @@ config DEV_COREDUMP
>  config DEBUG_DRIVER
>  	bool "Driver Core verbose debug messages"
>  	depends on DEBUG_KERNEL
> +	imply DEBUG_OPP

This should not be needed, otherwise we would have to do that for all
random driver subsystem in the kernel.

>  	help
>  	  Say Y here if you want the Driver core to produce a bunch of
>  	  debug messages to the system log. Select this if you are having a
> diff --git a/drivers/opp/Kconfig b/drivers/opp/Kconfig
> index e8ce47b32735..6a2d2c6c1143 100644
> --- a/drivers/opp/Kconfig
> +++ b/drivers/opp/Kconfig
> @@ -12,3 +12,10 @@ config PM_OPP
>  	  representing individual voltage domains and provides SOC
>  	  implementations a ready to use framework to manage OPPs.
>  	  For more information, read <file:Documentation/power/opp.rst>
> +
> +menu "Operating Performance Points (OPP)"
> +config DEBUG_OPP
> +	bool "Debug Operating Performance Points"
> +	help
> +	  enable opp debugging
> +endmenu
> diff --git a/drivers/opp/Makefile b/drivers/opp/Makefile
> index f65ed5985bb4..2589915eef95 100644
> --- a/drivers/opp/Makefile
> +++ b/drivers/opp/Makefile
> @@ -1,5 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0-only
> -ccflags-$(CONFIG_DEBUG_DRIVER)	:= -DDEBUG
> +ccflags-$(CONFIG_DEBUG_OPP)	:= -DDEBUG

This feels wrong, you shouldn't need a -DDEBUG for anything if all is
going correctly.  Why is opp so odd this way?  Just use the normal
dev_dbg() macros and all will be fine, nothing special should be needed
at all.

And don't use a config option for it either, no one will turn it on, it
needs to "just work" for all systems.

thanks,

greg k-h