linux-kernel - Re: [PATCH v4 7/7] usb: typec: mux: Add On Semi fsa4480 driver

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Message-ID: <YiXbg4QwgIgLh3LW@smile.fi.intel.com>
Date:   Mon, 7 Mar 2022 12:16:35 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH v4 7/7] usb: typec: mux: Add On Semi fsa4480 driver

On Sun, Mar 06, 2022 at 07:40:40PM -0800, Bjorn Andersson wrote:
> The ON Semiconductor FSA4480 is a USB Type-C port multimedia switch with
> support for analog audio headsets. It allows sharing a common USB Type-C
> port to pass USB2.0 signal, analog audio, sideband use wires and analog
> microphone signal.
> 
> Due to lacking upstream audio support for testing, the audio muxing is
> left untouched, but implementation of muxing the SBU lines is provided
> as a pair of Type-C mux and switch devices. This provides the necessary
> support for enabling the DisplayPort altmode on devices with this
> circuit.

...

> +static const struct regmap_config fsa4480_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.max_register = FSA4480_MAX_REGISTER,
> +};

You are using mutex for accessing hardware. Do you still need a regmap lock?
If so, add a comment to explain why.

...

> +		/* 15us to allow the SBU switch to turn off */
> +		usleep_range(15, 1000);

This is quite unusual range.

If you are fine with the long delay, why to stress the system on it?
Otherwise the use of 1000 is unclear.

That said, I would expect one of the below:

		usleep_range(15, 30);
		usleep_range(500, 1000);

...

> +	sw_desc.fwnode = dev->fwnode;

Please, don't dereference for fwnode explicitly. Use dev_fwnode().

...

> +	mux_desc.fwnode = dev->fwnode;

Ditto.

-- 
With Best Regards,
Andy Shevchenko