linux-kernel - Re: [PATCH RFC v2 3/5] drm/panel: ilitek-ili9881c: Add support for two-lane configuration

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Message-ID: <ng2vjguqrfrxhw6vdzcrrlzegkepfvzwz24zj2fqddkt2df3mw@7biqwyndc2vz>
Date: Sat, 26 Apr 2025 06:31:38 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Kory Maincent <kory.maincent@...tlin.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH RFC v2 3/5] drm/panel: ilitek-ili9881c: Add support for
 two-lane configuration

On Thu, Apr 24, 2025 at 05:07:41PM +0200, Kory Maincent wrote:
> Enable support for two-lane configuration which is done by setting the
> LANSEL_SW_EN and LANSEL_SW bits in the Pad Control register.
> 
> Use the data-lanes device tree parameter to configure the number of lanes.
> The default configuration remains set to four lanes.
> 
> Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
> ---
> 
> Change in v2:
> - Read the data-lanes parameter from the port endpoint and use
>   drm_of_get_data_lanes_count instead of of_property_read_u32.
> ---
>  drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 33 +++++++++++++++++++++++++--
>  1 file changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> index 28cd7560e5db1d5734b10babdb4e4e553c6e07d0..2e38dea28336f445cb6a074dbbec006f0659287a 100644
> --- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> +++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> @@ -16,6 +16,7 @@
>  
>  #include <drm/drm_mipi_dsi.h>
>  #include <drm/drm_modes.h>
> +#include <drm/drm_of.h>
>  #include <drm/drm_panel.h>
>  
>  #include <video/mipi_display.h>
> @@ -1263,6 +1264,21 @@ static int ili9881c_send_cmd_data(struct ili9881c *ctx, u8 cmd, u8 data)
>  	return 0;
>  }
>  
> +static int ili9881c_set_lanes_cfg(struct ili9881c *ctx)
> +{
> +	int ret;
> +
> +	if (ctx->dsi->lanes != 2)
> +		/* Nothing to do */
> +		return 0;
> +
> +	ret = ili9881c_switch_page(ctx, 1);
> +	if (ret)
> +		return ret;
> +
> +	return ili9881c_send_cmd_data(ctx, 0xB7, 0x3);
> +}
> +
>  static int ili9881c_prepare(struct drm_panel *panel)
>  {
>  	struct ili9881c *ctx = panel_to_ili9881c(panel);
> @@ -1295,6 +1311,10 @@ static int ili9881c_prepare(struct drm_panel *panel)
>  			return ret;
>  	}
>  
> +	ret = ili9881c_set_lanes_cfg(ctx);
> +	if (ret)
> +		return ret;
> +
>  	ret = ili9881c_switch_page(ctx, 0);
>  	if (ret)
>  		return ret;
> @@ -1503,8 +1523,9 @@ static const struct drm_panel_funcs ili9881c_funcs = {
>  
>  static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi)
>  {
> +	struct device_node *endpoint;
>  	struct ili9881c *ctx;
> -	int ret;
> +	int ret, lanes;
>  
>  	ctx = devm_kzalloc(&dsi->dev, sizeof(*ctx), GFP_KERNEL);
>  	if (!ctx)
> @@ -1545,11 +1566,19 @@ static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi)
>  	if (ret)
>  		return ret;
>  
> +	endpoint = of_graph_get_endpoint_by_regs(dsi->dev.of_node, -1, -1);
> +	lanes = drm_of_get_data_lanes_count(endpoint, 2, 4);
> +	of_node_put(endpoint);

I think you can use drm_of_get_data_lanes_count_ep() here.

> +	if (lanes == -EINVAL)
> +		lanes = 4;
> +	else if (lanes < 0)
> +		return lanes;
> +
>  	drm_panel_add(&ctx->panel);
>  
>  	dsi->mode_flags = ctx->desc->mode_flags;
>  	dsi->format = MIPI_DSI_FMT_RGB888;
> -	dsi->lanes = 4;
> +	dsi->lanes = lanes;
>  
>  	return mipi_dsi_attach(dsi);
>  }
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry