linux-kernel - Re: [PATCH v3 0/3] drm/rockchip: Add driver for the new DSI2 controller

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Message-ID: <20241209150619.33998-1-dse@thaumatec.com>
Date: Mon,  9 Dec 2024 16:06:08 +0100
From: Daniel Semkowicz <dse@...umatec.com>
To: heiko@...ech.de
Cc: Laurent.pinchart@...asonboard.com,
	andrzej.hajda@...el.com,
	andy.yan@...k-chips.com,
	conor+dt@...nel.org,
	devicetree@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	jernej.skrabec@...il.com,
	jonas@...boo.se,
	krzk+dt@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-rockchip@...ts.infradead.org,
	maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	neil.armstrong@...aro.org,
	quentin.schulz@...rry.de,
	rfoss@...nel.org,
	robh@...nel.org,
	tzimmermann@...e.de
Subject: Re: [PATCH v3 0/3] drm/rockchip: Add driver for the new DSI2 controller

Hello Heiko,

On 03.12.24 21:54, Heiko Stuebner wrote:
> This series adds a bridge and glue driver for the DSI2 controller found
> in the rk3588 soc from Rockchip, that is based on a Synopsis IP block.
> 
> As the manual states:
> The Display Serial Interface 2 (DSI-2) is part of a group of communication
> protocols defined by the MIPI Alliance. The MIPI DSI-2 Host Controller is
> a digital core that implements all protocol functions defined in the
> MIPI DSI-2 Specification.
> 
> 
> While the driver structure is very similar to the previous DSI controller,
> the programming model of the core is quite different, with a completely
> new register set.
> 
> Another notable difference is that the phy interface is variable now too
> in its width and some other settings.
> 

I did more tests with different LVDS displays. I tested following
configurations with DSI/LVDS bridge:
- 1024x600@...01
- 1024x768@...02
- 1280x800@...07
- 1366x768@...06

All of them worked without issues, except 1366x768.
With this resolution, video is blurry, and offset incorrectly
to the left. There are also repeating errors on the console:

  rockchip-drm display-subsystem: [drm] *ERROR* POST_BUF_EMPTY irq err at vp3

In correct operation with other resolutions, there is no error.
I am not sure if this is a problem in your series or rather in VOP2
driver.

I tried to track down the problem, and it seems to be a generic issue
when horizontal line width is not divisible by 4.
Lowering line width to 1364px fixes the issue, but of course I have two
vertical lines of black pixels on the right.
I also made some tests with 720x1280 DSI display. Lowering horizontal
line to 718px shows the same problem. With 720px and 716px it works
correctly.

Kind regards
Daniel