linux-kernel - Re: [PATCH 0/5] Add new features to nwl-dsi driver

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Date:   Fri, 4 Sep 2020 19:08:02 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     "Robert Chiras (OSS)" <robert.chiras@....nxp.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Fabio Estevam <festevam@...il.com>,
        Ondrej Jirman <megous@...ous.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH 0/5] Add new features to nwl-dsi driver

Hi Robert,
On Fri, Aug 28, 2020 at 02:13:27PM +0300, Robert Chiras (OSS) wrote:
> From: Robert Chiras <robert.chiras@....com>
> 
> This patch-set adds the new following features to the nwl-dsi bridge driver:
> 
> 1. Control Video PLL from nwl-dsi driver
> 
> Add support for the Video PLL into the nwl-dsi driver, in order
> to better control it's rate, depending on the requested video mode.
> Controlling the Video PLL from nwl-dsi is usefull, since it both drives the DC
> pixel-clock and DPHY phy_ref clock.
> On i.MX8MQ, the DC can be either DCSS or LCDIF.
> 
> 2. Add new property to nwl-dsi: clock-drop-level
> 
> This new property is usefull in order to use DSI panels with the nwl-dsi
> driver which require a higher overhead to the pixel-clock.
> For example, the Raydium RM67191 DSI Panel works with 132M pixel-clock,
> but it needs an overhead in order to work properly. So, the actual pixel-clock
> fed into the DSI DPI interface needs to be lower than the one used ad DSI output.
> This new property addresses this matter.
> 
> 3. Add support to handle both inputs for nwl-dsi: DCSS and LCDIF

Thanks. I've tested the drop-clock-level part with mxsfb on a Librem 5
devkit and it removes the slight flickering we've seen before (and which
could be worked around by reducing the input pixel clock so 1 and 3 are

Tested-by: Guido Günther <agx@...xcpu.org>

I've have added some comments to the individual patches and try to get
around to check out the DCSS part too.
Cheers,
 -- Guido

> 
> Laurentiu Palcu (1):
>   drm/bridge: nwl-dsi: add support for DCSS
> 
> Robert Chiras (4):
>   drm/bridge: nwl-dsi: Add support for video_pll
>   dt-bindings: display/bridge: nwl-dsi: Document video_pll clock
>   drm/bridge: nwl-dsi: Add support for clock-drop-level
>   dt-bindings: display/bridge: nwl-dsi: Document fsl,clock-drop-level
>     property
> 
>  .../bindings/display/bridge/nwl-dsi.yaml           |   7 +
>  drivers/gpu/drm/bridge/nwl-dsi.c                   | 338 ++++++++++++++++++++-
>  2 files changed, 336 insertions(+), 9 deletions(-)
> 
> -- 
> 2.7.4
>