Date:   Sat, 20 Jul 2019 23:09:22 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Robert Chiras <robert.chiras@....com>
Cc:     "marex@...x.de" <marex@...x.de>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "festevam@...il.com" <festevam@...il.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [EXT] Re: [PATCH 00/10] Improvements and fixes for mxsfb DRM
 driver

Hi Robert,
On Tue, Jul 16, 2019 at 04:54:50PM +0200, Guido Günther wrote:
> Hi Robert,
> On Fri, Jul 12, 2019 at 08:15:32AM +0000, Robert Chiras wrote:
> > Hi Guido,
> > 
> > On Jo, 2019-07-11 at 17:04 +0200, Guido Günther wrote:
> > > Hi Robert,
> > > On Wed, Jun 26, 2019 at 04:32:08PM +0300, Robert Chiras wrote:
> > > > 
> > > > This patch-set improves the use of eLCDIF block on iMX 8 SoCs (like
> > > > 8MQ, 8MM
> > > > and 8QXP). Following, are the new features added and fixes from
> > > > this
> > > > patch-set:
> > > > 
> > > > 1. Add support for drm_bridge
> > > > On 8MQ and 8MM, the LCDIF block is not directly connected to a
> > > > parallel
> > > > display connector, where an LCD panel can be attached, but instead
> > > > it is
> > > > connected to DSI controller. Since this DSI stands between the
> > > > display
> > > > controller (eLCDIF) and the physical connector, the DSI can be
> > > > implemented
> > > > as a DRM bridge. So, in order to be able to connect the mxsfb
> > > > driver to
> > > > the DSI driver, the support for a drm_bridge was needed in mxsfb
> > > > DRM
> > > > driver (the actual driver for the eLCDIF block).
> > > So I wanted to test this but with both my somewhat cleaned up nwl
> > > driver¹ and the nwl driver forward ported from the nxp vendor tree
> > > I'm
> > > looking at a black screen with current mainline - while my dcss
> > > forward
> > > port gives me nice output on mipi dsi. Do you have a tree that uses
> > > mipi
> > > dsi on imx8mq where I could look at to check for differences?
> > Somewhere on the pixel path (between the display controller and the
> > DSI) there is a block that inverts the polarity. I can't remember
> > exactly what was the role of this block, but the polarity is inverted
> > when eLCDIF is used in combination with the DSI.
> > If you take a look at my DSI driver from NXP releases (I guess you have
> > them), you will see there is a hack in mode_fixup:
> > 
> > unsigned int *flags = &mode->flags;
> > if (dsi->sync_pol {
> > 	*flags |= DRM_MODE_FLAG_PHSYNC;
> > 	*flags |= DRM_MODE_FLAG_PVSYNC;
> > 	*flags &= ~DRM_MODE_FLAG_NHSYNC;
> > 	*flags &= ~DRM_MODE_FLAG_NVSYNC;
> > } else {
> > 	*flags &= ~DRM_MODE_FLAG_PHSYNC;
> > 	*flags &= ~DRM_MODE_FLAG_PVSYNC;
> > 	*flags |= DRM_MODE_FLAG_NHSYNC;
> > 	*flags |= DRM_MODE_FLAG_NVSYNC;
> > }
> 
> Thanks for the suggestion! I'll try that.
>
> > 
> > I know it's not clean, but it works for now. You can try this in your
> > driver and see if it helps.
> > These days I will also take your nwl-dsi driver and test it, and also
> > add support for bridge and eLCDIF to see if I can make it work.
> 
> I have hacky bridge support over here already. Give me some days to
> clean it up and it might safe you some work.

Your suggestion above (plus some other fixes) worked and
mxsfb+nwl+mixel-dphy works over here. I'll try to send a v1 of the nwl
driver out during the week.
Cheers,
 -- Guido

> Cheers,
>  -- Guido
> 
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