linux-kernel - Re: [PATCH v2 2/2] drm/bridge: sii902x: Set input bus format based on bus-width

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Message-ID: <yhn2467hxdsfootza7rdgi3ixqzbyadfd2zeijzqddzevxkwdq@ylk63q4biwqk>
Date: Mon, 14 Oct 2024 10:44:32 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Wadim Egorov <w.egorov@...tec.de>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	Laurent.pinchart@...asonboard.com, jonas@...boo.se, jernej.skrabec@...il.com, 
	maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, 
	simona@...ll.ch, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, bbrezillon@...nel.org, conor+dt@...nel.org, krzk+dt@...nel.org, 
	robh@...nel.org, upstream@...ts.phytec.de
Subject: Re: [PATCH v2 2/2] drm/bridge: sii902x: Set input bus format based
 on bus-width

On Mon, Oct 07, 2024 at 10:52:13AM +0200, Wadim Egorov wrote:
> Introduce a bus-width property to define the number of parallel RGB
> input pins connected to the transmitter. The input bus formats are updated
> accordingly. If the property is not specified, default to 24-bit bus-width.
> 
> Signed-off-by: Wadim Egorov <w.egorov@...tec.de>
> ---
> v2:
>   - Use bus-width instead of data-lines as suggested by Krzysztof
>   - Handle default case separately as an error case
> ---
>  drivers/gpu/drm/bridge/sii902x.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c
> index 7f91b0db161e..3b9e4e1dec45 100644
> --- a/drivers/gpu/drm/bridge/sii902x.c
> +++ b/drivers/gpu/drm/bridge/sii902x.c
> @@ -180,6 +180,8 @@ struct sii902x {
>  	struct gpio_desc *reset_gpio;
>  	struct i2c_mux_core *i2cmux;
>  	bool sink_is_hdmi;
> +	u32 bus_width;
> +
>  	/*
>  	 * Mutex protects audio and video functions from interfering
>  	 * each other, by keeping their i2c command sequences atomic.
> @@ -477,6 +479,8 @@ static u32 *sii902x_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>  						     u32 output_fmt,
>  						     unsigned int *num_input_fmts)
>  {
> +
> +	struct sii902x *sii902x = bridge_to_sii902x(bridge);
>  	u32 *input_fmts;
>  
>  	*num_input_fmts = 0;
> @@ -485,7 +489,20 @@ static u32 *sii902x_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>  	if (!input_fmts)
>  		return NULL;
>  
> -	input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
> +	switch (sii902x->bus_width) {
> +	case 16:
> +		input_fmts[0] = MEDIA_BUS_FMT_RGB565_1X16;
> +		break;
> +	case 18:
> +		input_fmts[0] = MEDIA_BUS_FMT_RGB666_1X18;
> +		break;
> +	case 24:
> +		input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
> +		break;
> +	default:
> +		return NULL;
> +	}
> +
>  	*num_input_fmts = 1;
>  
>  	return input_fmts;
> @@ -1167,6 +1184,15 @@ static int sii902x_probe(struct i2c_client *client)
>  		return PTR_ERR(sii902x->reset_gpio);
>  	}
>  
> +	endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 0, -1);

More common pattern would be:

sii902x->bus_width = 24;
/* ignore the error */
if (endpoint)
	of_property_read_u32(endpoint, "bus-width", &sii902x->bus_width);


> +	if (endpoint) {
> +		ret = of_property_read_u32(endpoint, "bus-width", &sii902x->bus_width);
> +		if (ret) {
> +			dev_dbg(dev, "Could not get bus-width, defaulting to 24-bit bus-width\n");
> +			sii902x->bus_width = 24;

If endpoint isn't defined in DT (for whatever reasons), bus_width is also not set in the code.

> +		}
> +	}
> +
>  	endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1);
>  	if (endpoint) {
>  		struct device_node *remote = of_graph_get_remote_port_parent(endpoint);
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry