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SubjectRe: [PATCH 3/4] usb: typec: add TUSB320xA driver
Date
Heikki Krogerus <heikki.krogerus@linux.intel.com> writes:

> On Mon, Mar 07, 2022 at 10:17:04PM +0000, Alvin Šipraga wrote:
>> Hi Heikki,
>>
>> Heikki Krogerus <heikki.krogerus@linux.intel.com> writes:
>>
>> > Hi,
>> >
>> > On Tue, Mar 01, 2022 at 02:20:07PM +0100, Alvin Šipraga wrote:
>> >> From: Alvin Šipraga <alsi@bang-olufsen.dk>
>> >>
>> >> The TUSB320LA and TUSB320HA (or LAI, HAI) chips are I2C controlled
>> >> non-PD Type-C port controllers. They support detection of cable
>> >> orientation, port attachment state, and role, including Audio Accessory
>> >> and Debug Accessory modes. Add a typec class driver for this family.
>> >>
>> >> Note that there already exists an extcon driver for the TUSB320 (a
>> >> slightly older revision that does not support setting role preference or
>> >> disabling the CC state machine). This driver is loosely based on that
>> >> one.
>> >
>> > This looked mostly OK to me. There is one question below.
>> >
>> > <snip>
>> >
>> >> +static int tusb320xa_check_signature(struct tusb320xa *tusb)
>> >> +{
>> >> + static const char sig[] = { '\0', 'T', 'U', 'S', 'B', '3', '2', '0' };
>> >> + unsigned int val;
>> >> + int i, ret;
>> >> +
>> >> + mutex_lock(&tusb->lock);
>> >> +
>> >> + for (i = 0; i < sizeof(sig); i++) {
>> >> + ret = regmap_read(tusb->regmap, sizeof(sig) - 1 - i, &val);
>> >> + if (ret)
>> >> + goto done;
>> >> +
>> >> + if (val != sig[i]) {
>> >> + dev_err(tusb->dev, "signature mismatch!\n");
>> >> + ret = -ENODEV;
>> >> + goto done;
>> >> + }
>> >> + }
>> >> +
>> >> +done:
>> >> + mutex_unlock(&tusb->lock);
>> >> +
>> >> + return ret;
>> >> +}
>> >
>> > Couldn't that be done with a single read?
>> >
>> > char sig[8];
>> > u64 val;
>> >
>> > strcpy(sig, "TUSB320")
>> >
>> > mutex_lock(&tusb->lock);
>> >
>> > ret = regmap_raw_read(tusb->regmap, 0, &val, sizeof(val));
>> > ...
>> > if (val != cpu_to_le64(*(u64 *)sig)) {
>> > ...
>> >
>> > Something like that?
>>
>> I think it's a bit cryptic - are you sure it's worth it just to save 8
>> one-off regmap_read()s? I could also just remove this check... I see it
>> mostly as a courtesy to the user in case the I2C address in his device
>> tree mistakenly points to some other unsuspecting chip.
>>
>> BTW, do you have any feedback on the device tree bindings of this
>> series? Rob had some questions and I am not sure that my proposed
>> bindings are fully aligned with the typec subsystem expectations. Any
>> feedback would be welcome.
>
> I don't think I understand DT well enough to comment. I'm not
> completely sure what he's asking..

OK, no problem! Thanks for your reply.

Kind regards,
Alvin

>
>> I will wait for more comments and send a v2 in ~a week.
>
> thanks,
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