From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rob Herring <robh+dt@kernel.org>,
Daniel Scally <djrscally@gmail.com>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Hans de Goede <hdegoede@redhat.com>,
linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Subject: Re: [PATCH v4 7/7] usb: typec: mux: Add On Semi fsa4480 driver
Date: Mon, 7 Mar 2022 06:48:25 -0800 [thread overview]
Message-ID: <YiYbOQpX4+fP8S1W@ripper> (raw)
In-Reply-To: <YiXbg4QwgIgLh3LW@smile.fi.intel.com>
On Mon 07 Mar 02:16 PST 2022, Andy Shevchenko wrote:
> 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.
>
I've not considered that before, but you're right, there doesn't seem to
be any reason to keep the locking in the regmap.
> ...
>
> > + /* 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);
>
Glad you asked about that, as you say the typical form is to keep the
range within 2x of the lower value, or perhaps lower + 5.
But if the purpose is to specify a minimum time and then give a max to
give the system some flexibility in it's decision of when to wake up.
And in situations such as this, we're talking about someone connecting a
cable, so we're in "no rush" and I picked the completely arbitrary 1ms
as the max.
Do you see any drawback of this much higher number? (Other than it
looking "wrong")
> ...
>
> > + sw_desc.fwnode = dev->fwnode;
>
> Please, don't dereference for fwnode explicitly. Use dev_fwnode().
>
Okay, will update accordingly.
Thanks,
Bjorn
> ...
>
> > + mux_desc.fwnode = dev->fwnode;
>
> Ditto.
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
next prev parent reply other threads:[~2022-03-07 14:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-07 3:40 [PATCH v4 1/7] device property: Helper to match multiple connections Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 2/7] device property: Use multi-connection matchers for single case Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 3/7] usb: typec: mux: Check dev_set_name() return value Bjorn Andersson
2022-03-07 10:08 ` Andy Shevchenko
2022-03-07 14:33 ` Bjorn Andersson
2022-03-07 14:52 ` Heikki Krogerus
2022-03-07 3:40 ` [PATCH v4 4/7] usb: typec: mux: Introduce indirection Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 5/7] usb: typec: mux: Allow multiple mux_devs per mux Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 6/7] dt-bindings: usb: Add binding for fcs,fsa4480 Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 7/7] usb: typec: mux: Add On Semi fsa4480 driver Bjorn Andersson
2022-03-07 10:16 ` Andy Shevchenko
2022-03-07 14:48 ` Bjorn Andersson [this message]
2022-03-07 16:13 ` Andy Shevchenko
2022-03-07 21:04 ` Bjorn Andersson
2022-03-07 22:13 ` Andy Shevchenko
2022-03-08 0:01 ` Bjorn Andersson
2022-03-07 10:05 ` [PATCH v4 1/7] device property: Helper to match multiple connections Andy Shevchenko
2022-03-07 19:13 ` Bjorn Andersson
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