From: Alexander Stein <alexander.stein@systec-electronic.com>
To: Stefan Agner <stefan@agner.ch>
Cc: dri-devel@lists.freedesktop.org, shawnguo@kernel.org,
        kernel@pengutronix.de, airlied@linux.ie, daniel.vetter@ffwll.ch,
        jianwei.wang.chn@gmail.com, alison.wang@freescale.com, meng.yi@nxp.com,
        mturquette@baylibre.com, sboyd@codeaurora.org, mark.rutland@arm.com,
        robh+dt@kernel.org, pawel.moll@arm.com, ijc+devicetree@hellion.org.uk,
        galak@codeaurora.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 6/8] drm/fsl-dcu: add TCON driver
Date: Tue, 29 Mar 2016 08:45:33 +0200
Message-ID: <2234894.ri36D5MRrN@ws-stein>
User-Agent: KMail/4.14.10 (Linux/4.1.15-gentoo-r1; KDE/4.14.16; x86_64; ; )
In-Reply-To: <1459216802-32094-7-git-send-email-stefan@agner.ch>
References: <1459216802-32094-1-git-send-email-stefan@agner.ch> <1459216802-32094-7-git-send-email-stefan@agner.ch>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1618
Lines: 50

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@agner.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