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Date:   Tue, 14 Apr 2020 23:17:39 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     linux-kernel@vger.kernel.org,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nicolas Pitre <nico@fluxnic.net>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
        "David S. Miller" <davem@davemloft.net>,
        Saeed Mahameed <saeedm@mellanox.com>,
        Leon Romanovsky <leon@kernel.org>,
        dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org,
        netdev@vger.kernel.org, linux-rdma@vger.kernel.org
Subject: Re: [RFC 5/6] drm/rcar-du: fix selection of CMM driver
Message-ID: <20200414201739.GJ19819@pendragon.ideasonboard.com>
References: <20200408202711.1198966-1-arnd@arndb.de>
 <20200408202711.1198966-6-arnd@arndb.de>
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Hi Arnd,

Thank you for the patch.

On Wed, Apr 08, 2020 at 10:27:10PM +0200, Arnd Bergmann wrote:
> The 'imply' statement does not seem to have an effect, as it's
> still possible to turn the CMM code into a loadable module
> in a randconfig build, leading to a link error:
> 
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_enable':
> rcar_du_crtc.c:(.text+0xad4): undefined reference to `rcar_lvds_clk_enable'
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_disable':
> rcar_du_crtc.c:(.text+0xd7c): undefined reference to `rcar_lvds_clk_disable'
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_drv.o: in function `rcar_du_init':
> rcar_du_drv.c:(.init.text+0x4): undefined reference to `rcar_du_of_init'
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_encoder.o: in function `rcar_du_encoder_init':
> 
> Remove the 'imply', and instead use a silent symbol that defaults
> to the correct setting.

This will result in the CMM always being selected when DU is, increasing
the kernel size even for devices that don't need it. I believe we need a
better construct in Kconfig to fix this.

> Fixes: e08e934d6c28 ("drm: rcar-du: Add support for CMM")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/gpu/drm/rcar-du/Kconfig | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/Kconfig b/drivers/gpu/drm/rcar-du/Kconfig
> index 0919f1f159a4..5e35f5934d62 100644
> --- a/drivers/gpu/drm/rcar-du/Kconfig
> +++ b/drivers/gpu/drm/rcar-du/Kconfig
> @@ -4,7 +4,6 @@ config DRM_RCAR_DU
>  	depends on DRM && OF
>  	depends on ARM || ARM64
>  	depends on ARCH_RENESAS || COMPILE_TEST
> -	imply DRM_RCAR_CMM
>  	imply DRM_RCAR_LVDS
>  	select DRM_KMS_HELPER
>  	select DRM_KMS_CMA_HELPER
> @@ -15,9 +14,8 @@ config DRM_RCAR_DU
>  	  If M is selected the module will be called rcar-du-drm.
>  
>  config DRM_RCAR_CMM
> -	tristate "R-Car DU Color Management Module (CMM) Support"
> +	def_tristate DRM_RCAR_DU
>  	depends on DRM && OF
> -	depends on DRM_RCAR_DU
>  	help
>  	  Enable support for R-Car Color Management Module (CMM).
>  

-- 
Regards,

Laurent Pinchart