linux-kernel - Re: [PATCH] drm: pl111: add CONFIG_VEXPRESS

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Message-ID: <20200527145226.GA91560@ravnborg.org>
Date:   Wed, 27 May 2020 16:52:26 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Eric Anholt <eric@...olt.net>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        dri-devel@...ts.freedesktop.org,
        Alex Deucher <alexander.deucher@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: pl111: add CONFIG_VEXPRESS_CONFIG dependency

Hi Arnd.

On Wed, May 27, 2020 at 03:31:42PM +0200, Arnd Bergmann wrote:
> The vexpress_config code fails to link in some configurations:
> 
> drivers/gpu/drm/pl111/pl111_versatile.o: in function `pl111_versatile_init':
> (.text+0x1f0): undefined reference to `devm_regmap_init_vexpress_config'
> 
> Add a dependency that links to this only if the dependency is there,
> and prevent the configuration where the drm driver is built-in but
> the config is a loadable module.
> 
> Fixes: 826fc86b5903 ("drm: pl111: Move VExpress setup into versatile init")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Could this be another way to fix it:

diff --git a/drivers/gpu/drm/pl111/pl111_versatile.c b/drivers/gpu/drm/pl111/pl111_versatile.c
index 64f01a4e6767..1c38d3bd2e84 100644
--- a/drivers/gpu/drm/pl111/pl111_versatile.c
+++ b/drivers/gpu/drm/pl111/pl111_versatile.c
@@ -379,7 +379,7 @@ static int pl111_vexpress_clcd_init(struct device *dev, struct device_node *np,
        u32 val;
        int ret;

-       if (!IS_ENABLED(CONFIG_VEXPRESS_CONFIG))
+       if (!IS_REACHABLE(CONFIG_VEXPRESS_CONFIG))
                return -ENODEV;

        /*


Then we no longer have the whole driver depending on
the value of VEXPRESS_CONFIG.
Not that I like IS_REACHABLE() but we already had
IS_ENABLED() to cover up here, and that was not enough.

With your patch would we then need the IS_ENABLED()
check?

	Sam

> ---
>  drivers/gpu/drm/pl111/Kconfig           | 1 +
>  drivers/gpu/drm/pl111/pl111_versatile.c | 3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/pl111/Kconfig b/drivers/gpu/drm/pl111/Kconfig
> index 80f6748055e3..33a005816fdd 100644
> --- a/drivers/gpu/drm/pl111/Kconfig
> +++ b/drivers/gpu/drm/pl111/Kconfig
> @@ -3,6 +3,7 @@ config DRM_PL111
>  	tristate "DRM Support for PL111 CLCD Controller"
>  	depends on DRM
>  	depends on ARM || ARM64 || COMPILE_TEST
> +	depends on VEXPRESS_CONFIG || !VEXPRESS_CONFIG
>  	depends on COMMON_CLK
>  	select DRM_KMS_HELPER
>  	select DRM_KMS_CMA_HELPER
> diff --git a/drivers/gpu/drm/pl111/pl111_versatile.c b/drivers/gpu/drm/pl111/pl111_versatile.c
> index 64f01a4e6767..451d74205108 100644
> --- a/drivers/gpu/drm/pl111/pl111_versatile.c
> +++ b/drivers/gpu/drm/pl111/pl111_versatile.c
> @@ -476,7 +476,8 @@ int pl111_versatile_init(struct device *dev, struct pl111_drm_dev_private *priv)
>  	versatile_clcd_type = (enum versatile_clcd)clcd_id->data;
>  
>  	/* Versatile Express special handling */
> -	if (versatile_clcd_type == VEXPRESS_CLCD_V2M) {
> +	if (IS_ENABLED(CONFIG_VEXPRESS_CONFIG) &&
> +	    versatile_clcd_type == VEXPRESS_CLCD_V2M) {
>  		int ret = pl111_vexpress_clcd_init(dev, np, priv);
>  		of_node_put(np);
>  		if (ret)
> -- 
> 2.26.2