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From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Stefan Agner <stefan@agner.ch>
Cc:     linus.walleij@linaro.org, airlied@linux.ie, robh+dt@kernel.org,
        mark.rutland@arm.com, shawnguo@kernel.org, s.hauer@pengutronix.de,
        p.zabel@pengutronix.de, kernel@pengutronix.de,
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        a.hajda@samsung.com, gustavo@padovan.org,
        maarten.lankhorst@linux.intel.com, sean@poorly.run,
        marcel.ziswiler@toradex.com, max.krummenacher@toradex.com,
        dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 6/8] drm/imx: support handling bridge timings bus flags
Date:   Fri, 14 Sep 2018 13:00:29 +0300
Message-ID: <1666767.e3BgH42IGz@avalon>
Organization: Ideas on Board Oy
In-Reply-To: <20180912183222.25414-7-stefan@agner.ch>
References: <20180912183222.25414-1-stefan@agner.ch> <20180912183222.25414-7-stefan@agner.ch>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Stefan,

Thank you for the patch.

On Wednesday, 12 September 2018 21:32:20 EEST Stefan Agner wrote:
> A bridge might require specific settings for the pixel data on
> the bus. Copy the bus flags from the bridge timings if a bridge
> is in use.
> 
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
>  drivers/gpu/drm/imx/parallel-display.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/imx/parallel-display.c
> b/drivers/gpu/drm/imx/parallel-display.c index aefd04e18f93..7798a0621df7
> 100644
> --- a/drivers/gpu/drm/imx/parallel-display.c
> +++ b/drivers/gpu/drm/imx/parallel-display.c
> @@ -239,6 +239,9 @@ static int imx_pd_bind(struct device *dev, struct device
> *master, void *data) if (ret && ret != -ENODEV)
>  		return ret;
> 
> +	if (imxpd->bridge && imxpd->bridge->timings)
> +		imxpd->bus_flags = imxpd->bridge->timings->input_bus_flags;

As explained in different replies in this mail thread (and in v1), we need 
something more complex than this.

How about creating a helper function that would take a sampling edge, setup 
and hold times, clock frequency and internal delay on the driving side, and 
return which edge to drive the data on ? I agree with you that the logic is 
complex, so we shouldn't duplicate it in multiple drivers. If you submit such 
a patch I'll implement support for configuring the clock edge in the R-Car DU 
driver and test it with the ADV7123.

>  	imxpd->dev = dev;
> 
>  	ret = imx_pd_register(drm, imxpd);

-- 
Regards,

Laurent Pinchart