linux-kernel - Re: [PATCH v2 6/8] drm/fsl-dcu: add TCON driver

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Date:	Tue, 29 Mar 2016 08:45:33 +0200
From:	Alexander Stein <alexander.stein@...tec-electronic.com>
To:	Stefan Agner <stefan@...er.ch>
Cc:	dri-devel@...ts.freedesktop.org, shawnguo@...nel.org,
	kernel@...gutronix.de, airlied@...ux.ie, daniel.vetter@...ll.ch,
	jianwei.wang.chn@...il.com, alison.wang@...escale.com,
	meng.yi@....com, mturquette@...libre.com, sboyd@...eaurora.org,
	mark.rutland@....com, robh+dt@...nel.org, pawel.moll@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 6/8] drm/fsl-dcu: add TCON driver

Hi,

some comments below.

On Monday 28 March 2016 19:00:00, Stefan Agner wrote:
> Add driver for the TCON (timing controller) module. The TCON module
> is a separate module attached after the DCU (display controller
> unit). Each DCU instance has its own, directly connected TCON
> instance. The DCU's RGB and timing signals are passing through
> the TCON module. TCON can provide timing signals for raw TFT panels
> or operate in a bypass mode which leaves all signals unaltered.
> 
> The driver currently only supports the bypass mode.
> 
> Signed-off-by: Stefan Agner <stefan@...er.ch>

> --- a/Documentation/devicetree/bindings/display/fsl,dcu.txt
> +++ b/Documentation/devicetree/bindings/display/fsl,dcu.txt
> @@ -14,6 +14,7 @@ Required properties:
>  Optional properties:
>  - clocks:		Second handle for pixel clock.
>  - clock-names:		Second name "pix" for pixel clock.
> +- fsl,tcon:		The phandle to the timing controller node.

Maybe a comment this is (currently) only for Vybrid, but not LS1021A.

> --- /dev/null
> +++ b/drivers/gpu/drm/fsl-dcu/fsl_tcon.c
> [...]
> +struct fsl_tcon *fsl_tcon_init(struct device *dev)
> +{
> +	struct fsl_tcon *tcon;
> +	struct device_node *np;
> +	int ret;
> +
> +	tcon = devm_kzalloc(dev, sizeof(*tcon), GFP_KERNEL);
> +	if (!tcon)
> +		return NULL;
> +
> +	np = of_parse_phandle(dev->of_node, "fsl,tcon", 0);
> +	if (!np) {
> +		dev_warn(dev, "Couldn't find the tcon node\n");
> +		return NULL;
> +	}

Maybe check for device tree node before allocating struct fsl_tcon? Also this 
should not be a warning, as on LS1021A this is to be expected.

Best regards,
Alexander