Re: [PATCH 4/8] drm/rockchip: Use drm_gem_fb_create_with_dirty

From: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
	DRI Development <dri-devel@lists.freedesktop.org>
Cc: linux-rockchip@lists.infradead.org,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	linux-arm-kernel@lists.infradead.org,
	Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH 4/8] drm/rockchip: Use drm_gem_fb_create_with_dirty
Date: Wed, 27 Nov 2019 18:33:07 +0100	[thread overview]
Message-ID: <023053cb-9f72-c29a-ec2f-cf7532ff5c43@collabora.com> (raw)
In-Reply-To: <20191115092120.4445-5-daniel.vetter@ffwll.ch>

Hi Daniel,

After applying this patch there are some slight differences
in the effective behavior of the code.

I can't tell if they are important, please see below.

Andrzej

W dniu 15.11.2019 o 10:21, Daniel Vetter pisze:
> If rockchip would switch over to the generic fbdev setup we could
> grabage collect even more of all this code (all of the remaining fb
> handling code really).
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Sandy Huang <hjc@rock-chips.com>
> Cc: "Heiko Stübner" <heiko@sntech.de>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-rockchip@lists.infradead.org
> ---
>   drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 54 +---------------------
>   1 file changed, 1 insertion(+), 53 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> index ca01234c037c..081dbdaa0b07 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> @@ -53,64 +53,12 @@ rockchip_fb_alloc(struct drm_device *dev, const struct drm_mode_fb_cmd2 *mode_cm
>   	return fb;
>   }
>   
> -static struct drm_framebuffer *
> -rockchip_user_fb_create(struct drm_device *dev, struct drm_file *file_priv,
> -			const struct drm_mode_fb_cmd2 *mode_cmd)
> -{
> -	const struct drm_format_info *info = drm_get_format_info(dev,
> -								 mode_cmd);
> -	struct drm_framebuffer *fb;
> -	struct drm_gem_object *objs[ROCKCHIP_MAX_FB_BUFFER];
> -	struct drm_gem_object *obj;
> -	int num_planes = min_t(int, info->num_planes, ROCKCHIP_MAX_FB_BUFFER);
> -	int ret;
> -	int i;
> -
> -	for (i = 0; i < num_planes; i++) {

drm_gem_fb_create_with_funcs(), if no error happens,
iterates exactly info->num_planes times,
but the function being removed here iterates
min_t(int, info->num_planes, 3) times.

Is it ensured earlier elsewhere that info->num_planes does not exceed 3?

> -		unsigned int width = mode_cmd->width / (i ? info->hsub : 1);
> -		unsigned int height = mode_cmd->height / (i ? info->vsub : 1);
> -		unsigned int min_size;
> -
> -		obj = drm_gem_object_lookup(file_priv, mode_cmd->handles[i]);
> -		if (!obj) {
> -			DRM_DEV_ERROR(dev->dev,
> -				      "Failed to lookup GEM object\n");
> -			ret = -ENXIO;
> -			goto err_gem_object_unreference;
> -		}
> -
> -		min_size = (height - 1) * mode_cmd->pitches[i] +
> -			mode_cmd->offsets[i] +
> -			width * info->cpp[i];

This computation in drm_gem_fb_create_with_funcs looks like this:

		min_size = (height - 1) * mode_cmd->pitches[i]
			 + drm_format_info_min_pitch(info, i, width)
			 + mode_cmd->offsets[i];

Perhaps that's actually the same thing?

> -
> -		if (obj->size < min_size) {
> -			drm_gem_object_put_unlocked(obj);
> -			ret = -EINVAL;
> -			goto err_gem_object_unreference;
> -		}
> -		objs[i] = obj;
> -	}
> -
> -	fb = rockchip_fb_alloc(dev, mode_cmd, objs, i);
> -	if (IS_ERR(fb)) {
> -		ret = PTR_ERR(fb);
> -		goto err_gem_object_unreference;
> -	}
> -
> -	return fb;
> -
> -err_gem_object_unreference:
> -	for (i--; i >= 0; i--)
> -		drm_gem_object_put_unlocked(objs[i]);
> -	return ERR_PTR(ret);
> -}
> -
>   static const struct drm_mode_config_helper_funcs rockchip_mode_config_helpers = {
>   	.atomic_commit_tail = drm_atomic_helper_commit_tail_rpm,
>   };
>   
>   static const struct drm_mode_config_funcs rockchip_drm_mode_config_funcs = {
> -	.fb_create = rockchip_user_fb_create,
> +	.fb_create = drm_gem_fb_create,

That way you leave out the ->dirty() callback from
static const struct drm_framebuffer_funcs rockchip_drm_fb_funcs

I'd say instead:

struct drm_framebuffer *
rockchip_gem_fb_create(struct drm_device *dev, struct drm_file *file,
		       const struct drm_mode_fb_cmd2 *mode_cmd)
{
	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
					    &rockchip_drm_fb_funcs);
}

and then

+	.fb_create = rockchip_gem_fb_create,

>   	.output_poll_changed = drm_fb_helper_output_poll_changed,
>   	.atomic_check = drm_atomic_helper_check,
>   	.atomic_commit = drm_atomic_helper_commit,
> 

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