linux-kernel - Re: [PATCH v14 07/10] drm/bridge: anx7625: Register Type C mode switches

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Message-ID: <ZBrjZj0VL20y1MUC@smile.fi.intel.com>
Date:   Wed, 22 Mar 2023 13:15:50 +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 <rfoss@...nel.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>,
        Xin Ji <xji@...logixsemi.com>, linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-acpi@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Lyude Paul <lyude@...hat.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Allen Chen <allen.chen@....com.tw>,
        dri-devel@...ts.freedesktop.org, Marek Vasut <marex@...x.de>,
        Stephen Boyd <swboyd@...omium.org>,
        chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org
Subject: Re: [PATCH v14 07/10] drm/bridge: anx7625: Register Type C mode
 switches

On Wed, Mar 22, 2023 at 06:46:36PM +0800, Pin-yen Lin wrote:
> Register USB Type-C mode switches when the "mode-switch" property and
> relevant ports are available in Device Tree. Configure the crosspoint
> switch based on the entered alternate mode for a specific Type-C
> connector.
> 
> Crosspoint switch can also be used for switching the output signal for
> different orientations of a single USB Type-C connector, but the
> orientation switch is not implemented yet. A TODO is added for this.

...

> +static int anx7625_typec_mux_set(struct typec_mux_dev *mux,
> +				 struct typec_mux_state *state)
> +{
> +	struct drm_dp_typec_port_data *port = typec_mux_get_drvdata(mux);
> +	struct anx7625_data *ctx = port->data;
> +	struct device *dev = ctx->dev;
> +	struct drm_dp_typec_switch_desc switch_desc = ctx->switch_desc;
> +	bool new_dp_connected, old_dp_connected;
> +
> +	if (switch_desc.num_typec_switches == 1)
> +		return 0;

> +	wait_for_completion(&ctx->mux_register);

How do we guarantee this won't become an infinite waiting?
Perhaps a comment explaining that?

> +	old_dp_connected = ctx->port_data[0].dp_connected ||
> +			   ctx->port_data[1].dp_connected;
> +
> +	ctx->port_data[port->port_num].dp_connected =
> +		state->alt &&
> +		state->alt->svid == USB_TYPEC_DP_SID &&
> +		state->alt->mode == USB_TYPEC_DP_MODE;
> +
> +	dev_dbg(dev, "mux_set dp_connected: c0=%d, c1=%d\n",
> +		ctx->port_data[0].dp_connected, ctx->port_data[1].dp_connected);
> +
> +	new_dp_connected = ctx->port_data[0].dp_connected ||
> +			   ctx->port_data[1].dp_connected;
> +
> +	/* DP on, power on first */
> +	if (!old_dp_connected && new_dp_connected)
> +		pm_runtime_get_sync(dev);
> +
> +	anx7625_typec_two_ports_update(ctx);
> +
> +	/* DP off, power off last */
> +	if (old_dp_connected && !new_dp_connected)
> +		pm_runtime_put_sync(dev);
> +
> +	return 0;
> +}

...

> +	struct device_node *port_node = of_graph_get_port_by_id(dev->of_node, 1);

You use fwnode below, so why not fwnode_graph_...(dev_fwnode(dev), ...) ?

> +	struct drm_dp_typec_switch_desc *switch_desc = &ctx->switch_desc;
> +	int ret;
> +	u32 dp_lanes[4];
> +	unsigned int i, num_lanes;
> +
> +	/*
> +	 * Currently, only mode switch is implemented.
> +	 * TODO: Implement Type-C orientation switch for anx7625.
> +	 */
> +	ret = drm_dp_register_typec_switches(dev, &port_node->fwnode,
> +					     &ctx->switch_desc, ctx,
> +					     anx7625_typec_mux_set);
> +	if (ret)
> +		return ret;
> +
> +	ctx->port_data = devm_kcalloc(dev, switch_desc->num_typec_switches,
> +				      sizeof(struct anx7625_typec_port_data),

				      sizeof(*ctx->port_data),

?

> +				      GFP_KERNEL);
> +	if (!ctx->port_data) {
> +		ret = -ENOMEM;
> +		goto unregister_mux;
> +	}

...

> +struct anx7625_typec_port_data {
> +	bool dp_connected;
> +	enum typec_orientation orientation;

Most likely enum will be 32-bit and bool 8-bit. Which means that the data type
size become 8 bytes for no reason. Can you swap the lines and perhaps check this
with `pahole` tool?

> +};

-- 
With Best Regards,
Andy Shevchenko