[PATCH 02/21] drm/msm/dsi: fix DSC width for the bonded DSI case

[Marijn Suijten]

On 2024-09-03 11:50:36, Marijn Suijten wrote:
> On 2024-08-29 18:17:31, Jun Nie wrote:
> > From: Jonathan Marek <jonathan at marek.ca>
> > 
> > For the bonded DSI case, DSC pic_width and timing calculations should use
> > the width of a single panel instead of the total combined width.
> 
> When this patch was originally proposed we already discussed [1] that this is
> **not** universally true.  On my hardware a single bonded panel always receives
> the full width, at least on downstream kernels, and it works [2].
> 
> [1]: https://lore.kernel.org/linux-arm-msm/eanx45rnasj7lu3r2tfhtg4qkqkcidd6zctsz6ci6jlklu4fgi@3nf73w2ka4li/T/#u
> [2]: https://gitlab.freedesktop.org/drm/msm/-/issues/41
> 
> Can we please figure this out before landing this patch?

For completeness I've picked this patch, together with the following
mis-squashed change from patch 03/21:

	diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
	index 7a4d9c071be5a..5abade8f26b88 100644
	--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
	+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
	@@ -953,7 +953,7 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
	 			return;
	 		}
 
	-		dsc->pic_width = mode->hdisplay;
	+		dsc->pic_width = hdisplay;
	 		dsc->pic_height = mode->vdisplay;
	 		DBG("Mode %dx%d\n", dsc->pic_width, dsc->pic_height);

And this is what it looks like on a bonded DSI CMD-mode display:
https://gitlab.freedesktop.org/drm/msm/-/issues/41#note_2553207
https://gitlab.freedesktop.org/-/project/2206/uploads/dc5c53d09ecb635fdc9f190fbc9b37ac/1000027079.jpg

That's a clear regression :)

- Marijn