linux-kernel - Re: [PATCH v2] drm/imx: imx-ldb: Add DDC support

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Message-ID: <1461748450.4044.18.camel@pengutronix.de>
Date:	Wed, 27 Apr 2016 11:14:10 +0200
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Akshay Bhat <akshay.bhat@...esys.com>
Cc:	airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v2] drm/imx: imx-ldb: Add DDC support

Hi Akshay,

Am Dienstag, den 26.04.2016, 13:40 -0400 schrieb Akshay Bhat:
> From: Steve Longerbeam <steve_longerbeam@...tor.com>
> 
> Add support for reading EDID over Display Data Channel. If no DDC
> adapter is available, falls back to hardcoded EDID or display-timings
> node as before.
> 
> Signed-off-by: Steve Longerbeam <steve_longerbeam@...tor.com>
> Signed-off-by: Akshay Bhat <akshay.bhat@...esys.com>
> Acked-by: Philipp Zabel <p.zabel@...gutronix.de>
> ---
> 
> Hi Philipp,
> 
> I found this patch to add DDC support to imx-ldb at:
> https://patchwork.kernel.org/patch/5207231/
> 
> Looks like it never made it to the upstream kernel.
> I have rebased this on 4.6-rc5 and tested the same.

Thanks for picking this up. Please also update the binding docs in
Documentation/devicetree/bindings/display/imx/ldb.txt.

> Thanks,
> Akshay
> 
> v1 -> v2:
> Rebase to 4.6-rc5
> Add check for channel->panel before fallback to display-timings node 
> 
>  drivers/gpu/drm/imx/imx-ldb.c | 38 ++++++++++++++++++++++++++++++--------
>  1 file changed, 30 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
> index a58eee5..67706c9 100644
> --- a/drivers/gpu/drm/imx/imx-ldb.c
> +++ b/drivers/gpu/drm/imx/imx-ldb.c
> @@ -59,6 +59,7 @@ struct imx_ldb_channel {
>  	struct drm_encoder encoder;
>  	struct drm_panel *panel;
>  	struct device_node *child;
> +	struct i2c_adapter *ddc;
>  	int chno;
>  	void *edid;
>  	int edid_len;
> @@ -107,6 +108,9 @@ static int imx_ldb_connector_get_modes(struct drm_connector *connector)
>  			return num_modes;
>  	}
>  
> +	if (!imx_ldb_ch->edid && imx_ldb_ch->ddc)
> +		imx_ldb_ch->edid = drm_get_edid(connector, imx_ldb_ch->ddc);
> +
>  	if (imx_ldb_ch->edid) {
>  		drm_mode_connector_update_edid_property(connector,
>  							imx_ldb_ch->edid);
> @@ -554,6 +558,7 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
>  	for_each_child_of_node(np, child) {
>  		struct imx_ldb_channel *channel;
>  		struct device_node *port;
> +		struct device_node *ddc_node;

For alphabetic and/or aesthetic reasons, would you mind moving this up
one line?
 
>  		ret = of_property_read_u32(child, "reg", &i);
>  		if (ret || i < 0 || i > 1)
> @@ -595,14 +600,30 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
>  			}
>  		}
>  
> -		edidp = of_get_property(child, "edid", &channel->edid_len);
> -		if (edidp) {
> -			channel->edid = kmemdup(edidp, channel->edid_len,
> -						GFP_KERNEL);
> -		} else if (!channel->panel) {
> -			ret = of_get_drm_display_mode(child, &channel->mode, 0);
> -			if (!ret)
> -				channel->mode_valid = 1;
> +		ddc_node = of_parse_phandle(child, "ddc-i2c-bus", 0);
> +		if (ddc_node) {
> +			channel->ddc = of_find_i2c_adapter_by_node(ddc_node);

If channel->ddc is NULL after this, we should probably warn.

> +			of_node_put(ddc_node);
> +		}
> +
> +		if (!channel->ddc) {
> +			/* if no DDC available, fallback to hardcoded EDID */
> +			dev_dbg(dev, "no ddc available\n");
> +
> +			edidp = of_get_property(child, "edid",
> +						&channel->edid_len);
> +			if (edidp) {
> +				channel->edid = kmemdup(edidp,
> +							channel->edid_len,
> +							GFP_KERNEL);
> +			} else if (!channel->panel) {
> +				/* fallback to display-timings node */
> +				ret = of_get_drm_display_mode(child,
> +							      &channel->mode,
> +							      0);
> +				if (!ret)
> +					channel->mode_valid = 1;
> +			}
>  		}
>  
>  		channel->bus_format = of_get_bus_format(dev, child);
> @@ -647,6 +668,7 @@ static void imx_ldb_unbind(struct device *dev, struct device *master,
>  		channel->encoder.funcs->destroy(&channel->encoder);
>  
>  		kfree(channel->edid);
> +		i2c_put_adapter(channel->ddc);
>  	}
>  }
>  

regards
Philipp