linux-kernel - Re: [PATCH V6 3/5] tty: serial: meson: Describes the calculation of the UART baud rate clock using a clock frame

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Message-ID: <21eea0cd-5bf1-dec6-a776-f417aefa5bda@amlogic.com>
Date:   Wed, 19 Jan 2022 14:00:44 +0800
From:   Yu Tu <yu.tu@...ogic.com>
To:     Jiri Slaby <jirislaby@...nel.org>, <linux-serial@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH V6 3/5] tty: serial: meson: Describes the calculation of
 the UART baud rate clock using a clock frame

Hi Jiri,
	Thank you very much for your patient reply.I learned a lot from your 
response.

On 2022/1/18 17:39, Jiri Slaby wrote:
> [ EXTERNAL EMAIL ]
> 
> On 18. 01. 22, 4:09, Yu Tu wrote:
>> Using the common Clock code to describe the UART baud rate clock
>> makes it easier for the UART driver to be compatible with the
>> baud rate requirements of the UART IP on different meson chips.
> ...
>> --- a/drivers/tty/serial/meson_uart.c
>> +++ b/drivers/tty/serial/meson_uart.c
> ...
>> @@ -629,57 +640,105 @@ static struct uart_driver meson_uart_driver = {
>>       .cons        = MESON_SERIAL_CONSOLE,
>>   };
>> -static inline struct clk *meson_uart_probe_clock(struct device *dev,
>> -                         const char *id)
>> -{
>> -    struct clk *clk = NULL;
>> -    int ret;
>> -
>> -    clk = devm_clk_get(dev, id);
>> -    if (IS_ERR(clk))
>> -        return clk;
>> -
>> -    ret = clk_prepare_enable(clk);
>> -    if (ret) {
>> -        dev_err(dev, "couldn't enable clk\n");
>> -        return ERR_PTR(ret);
>> -    }
>> -
>> -    devm_add_action_or_reset(dev,
>> -            (void(*)(void *))clk_disable_unprepare,
>> -            clk);
>> -
>> -    return clk;
>> -}
>> +static struct clk_div_table xtal_div_table[] = {
> 
> This can be const, right?
You are right.
> 
>> +    {0, 3},
>> +    {1, 1},
>> +    {2, 2},
>> +    {3, 2},
> 
> Not sure if you didn't remove too much whitespace. I think it should be 
> like: "{ 0, 3 },". But I actually don't care, it's a minor thing.
> 
Ok, I will correct it if it needs to be changed.
> I cannot comment on the rest (clk and OF part) as my knowledge is pretty 
> limited there. Leaving up to others.
> 
Anyway, thanks for your reply.
> thanks,