linux-kernel - Re: [PATCH 4/4] drm/msm: Fix default fb var width and height

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Date:	Fri, 6 Mar 2015 13:12:47 -0500
From:	Rob Clark <robdclark@...il.com>
To:	Hai Li <hali@...eaurora.org>
Cc:	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Daniel Vetter <daniel@...ll.ch>,
	Dave Airlie <airlied@...il.com>
Subject: Re: [PATCH 4/4] drm/msm: Fix default fb var width and height

On Thu, Mar 5, 2015 at 3:20 PM, Hai Li <hali@...eaurora.org> wrote:
> The framebuffer var width and height should reflect the size of
> framebuffer memory allocated, which is the entire surface size.
>
> In case of dual DSI connectors with TILE properties, this change
> makes the whole image show on the dual DSI panel, instead of
> duplicated images on both sides.
>
> Signed-off-by: Hai Li <hali@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/msm_fbdev.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
> index df60f65..d3e8b14 100644
> --- a/drivers/gpu/drm/msm/msm_fbdev.c
> +++ b/drivers/gpu/drm/msm/msm_fbdev.c
> @@ -169,7 +169,8 @@ static int msm_fbdev_create(struct drm_fb_helper *helper,
>         }
>
>         drm_fb_helper_fill_fix(fbi, fb->pitches[0], fb->depth);
> -       drm_fb_helper_fill_var(fbi, helper, sizes->fb_width, sizes->fb_height);
> +       drm_fb_helper_fill_var(fbi, helper,
> +                       sizes->surface_width, sizes->surface_height);
>

so, I believe the intention for separation if surface_width/height and
fb_width/height, it to allocate a buffer that is big enough (width and
height) for all connected displays (so as to not leave some display
scanning out too small of a buffer), but size the fbdev buffer small
enough that text would be visible on all screens.  Using
surface_width/height here instead of fb_width/height would break that.

But I think I have a different idea.. we could implement fb helper
func initial_config() to just call drm_pick_crtcs() (which we'd have
to export), and then for each of the crtcs[n] connected to a connector
with TILE property, populate the offsets[n].x/y.  Or possibly we
should just make drm_setup_crtcs() clever enough to do that
automatically.. that would result in larger fb_size and the two crtc's
scanning out their own parts of the buffer.

BR,
-R

>         dev->mode_config.fb_base = paddr;
>
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
>
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