linux-kernel - Re: [PATCH v6 7/7] drm/bridge: it6505: Register Type C mode switches

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Date:   Thu, 24 Nov 2022 14:23:34 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Pin-yen Lin <treapking@...omium.org>
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Prashant Malani <pmalani@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Stephen Boyd <swboyd@...omium.org>,
        dri-devel@...ts.freedesktop.org,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        devicetree@...r.kernel.org, chrome-platform@...ts.linux.dev,
        linux-acpi@...r.kernel.org, Marek Vasut <marex@...x.de>,
        Xin Ji <xji@...logixsemi.com>, Lyude Paul <lyude@...hat.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-kernel@...r.kernel.org, Allen Chen <allen.chen@....com.tw>
Subject: Re: [PATCH v6 7/7] drm/bridge: it6505: Register Type C mode switches

On Thu, Nov 24, 2022 at 06:20:56PM +0800, Pin-yen Lin wrote:
> Register USB Type-C mode switches when the "mode-switch" property and
> relevant port are available in Device Tree. Configure the "lane_swap"
> state based on the entered alternate mode for a specific Type-C
> connector, which ends up updating the lane swap registers of the it6505
> chip.

...

>  config DRM_ITE_IT6505
>          tristate "ITE IT6505 DisplayPort bridge"
>          depends on OF
> +	depends on TYPEC || TYPEC=n
>  	select DRM_DISPLAY_DP_HELPER
>  	select DRM_DISPLAY_HDCP_HELPER
>  	select DRM_DISPLAY_HELPER

Something went wrong with the indentation. Perhaps you need to fix it first.

...

>  #include <drm/drm_edid.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_probe_helper.h>
> +#include <drm/drm_of.h>

Make it ordered?

...

> +struct it6505_port_data {

> +	bool dp_connected;

Perhaps make it last?

> +	struct typec_mux_dev *typec_mux;
> +	struct it6505 *it6505;
> +};

...

> +static void it6505_typec_ports_update(struct it6505 *it6505)
> +{
> +	usleep_range(3000, 4000);
> +
> +	if (it6505->typec_ports[0].dp_connected && it6505->typec_ports[1].dp_connected)
> +		/* Both ports available, do nothing to retain the current one. */
> +		return;
> +	else if (it6505->typec_ports[0].dp_connected)
> +		it6505->lane_swap = false;
> +	else if (it6505->typec_ports[1].dp_connected)
> +		it6505->lane_swap = true;
> +
> +	usleep_range(3000, 4000);
> +}

As per previous patch comments.

Also, comment out these long sleeps. Why they are needed.

...

> +		int ret = pm_runtime_get_sync(dev);
> +
> +		/*
> +		 * On system resume, mux_set can be triggered before
> +		 * pm_runtime_force_resume re-enables runtime power management.

We refer to the functions as func().

> +		 * Handling the error here to make sure the bridge is powered on.
> +		 */
> +		if (ret < 0)
> +			it6505_poweron(it6505);

This seems needed a bit more of explanation, esp. why you leave PM runtime
reference count bumped up.

...

> +	num_lanes = drm_of_get_data_lanes_count(node, 0, 2);
> +	if (num_lanes <= 0) {
> +		dev_err(dev, "Error on getting data lanes count: %d\n",
> +			num_lanes);
> +		return num_lanes;
> +	}
> +
> +	ret = of_property_read_u32_array(node, "data-lanes", dp_lanes, num_lanes);
> +	if (ret) {
> +		dev_err(dev, "Failed to read the data-lanes variable: %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	for (i = 0; i < num_lanes; i++) {
> +		if (port_num != -1 && port_num != dp_lanes[i] / 2) {
> +			dev_err(dev, "Invalid data lane numbers\n");
> +			return -EINVAL;
> +		}

As per previous patch comments.

> +		port_num = dp_lanes[i] / 2;
> +	}

The above seems like tons of duplicating code that drivers need to implement.
Can we shrink that burden by adding some library functions?

-- 
With Best Regards,
Andy Shevchenko