linux-kernel - Re: [PATCH V2 1/2] tty: serial: meson: Add a 12MHz internal clock rate to calculate baud rate in order to meet the baud rate requirements of special BT modules

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Message-ID: <0d76ba66-9e2c-510d-780e-26fe9626c1a5@baylibre.com>
Date:   Thu, 21 Apr 2022 10:44:38 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Jiri Slaby <jirislaby@...nel.org>
Cc:     Yu Tu <yu.tu@...ogic.com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        linux-amlogic <linux-amlogic@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH V2 1/2] tty: serial: meson: Add a 12MHz internal clock
 rate to calculate baud rate in order to meet the baud rate requirements of
 special BT modules

Hi Andy,

On 19/04/2022 10:21, Andy Shevchenko wrote:
> On Tue, Apr 19, 2022 at 10:38 AM Jiri Slaby <jirislaby@...nel.org> wrote:
>> On 19. 04. 22, 9:29, Yu Tu wrote:
>>> On 2022/4/18 20:09, Andy Shevchenko wrote:
>>>> On Mon, Apr 18, 2022 at 8:50 AM Yu Tu <yu.tu@...ogic.com> wrote:
> 
> ...
> 
>>>>> +struct meson_uart_data {
>>>>> +       bool has_xtal_div2;
>>>>
>>>> I would prefer to see this as an unsigned int and with a less
>>>> particular name, e.g. xtal_div would suffice.
>>> I don't have a problem with your suggestion.Let's see What Neil has to say.
>>
>> Actually why uint provided it's a boolean value? Or do you mean to store
>> the divisor directly in this member, Andy?
> 
> Yes I was thinking to provide the value and then always provide the
> private data. In such cases we don't need an additional condition.
> 

Actually, the original boolean "has_xtal_div2" is right because it encodes
if the HW has an internal /2 divider for the XTAL clock input path.

The HW historically has a /3 divider on the same path, and new HW now has both.

So the boolean indicates if the /2 divider is present so it can be used.

So I'm in favour of keeping the boolean type.
For the naming, it seems appropriate for me.

Neil