linux-kernel - Re: [PATCH V3 3/4] 8250: 8250_f81504: Add Fintek F81504/508/512 PCIE-to-UART/GPIO UART support

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Date:	Wed, 17 Feb 2016 17:30:15 +0800
From:	Peter Hung <hpeter@...il.com>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linus.walleij@...aro.org, gnurou@...il.com,
	gregkh@...uxfoundation.org, paul.gortmaker@...driver.com,
	lee.jones@...aro.org, jslaby@...e.com, gnomes@...rguk.ukuu.org.uk,
	peter_hong@...tek.com.tw
Cc:	heikki.krogerus@...ux.intel.com, peter@...leysoftware.com,
	soeren.grunewald@...y.de, udknight@...il.com,
	adam.lee@...onical.com, arnd@...db.de, manabian@...il.com,
	scottwood@...escale.com, yamada.masahiro@...ionext.com,
	paul.burton@...tec.com, mans@...sr.com, matthias.bgg@...il.com,
	ralf@...ux-mips.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org, linux-serial@...r.kernel.org,
	tom_tsai@...tek.com.tw, Peter Hung <hpeter+linux_kernel@...il.com>
Subject: Re: [PATCH V3 3/4] 8250: 8250_f81504: Add Fintek F81504/508/512
 PCIE-to-UART/GPIO UART support

Hi Andy,

Andy Shevchenko 於 2016/2/16 下午 05:11 寫道:
> On Tue, 2016-02-16 at 14:55 +0800, Peter Hung wrote:
>> +static u32 baudrate_table[] = { 1500000, 1152000, 921600 };
>> +static u8 clock_table[] = { F81504_CLKSEL_24_MHZ,
>> F81504_CLKSEL_18DOT46_MHZ,
>> +				F81504_CLKSEL_14DOT77_MHZ };
>
> I suggest to replace DOT by _.

ok

>> +/* We should do proper H/W transceiver setting before change to
>> RS485 mode */
>> +static int f81504_rs485_config(struct uart_port *port,
>> +			       struct serial_rs485 *rs485)
>> +{
>> +	u8 setting;
>> +	u8 *index = (u8 *) port->private_data;
>
> private_data is a type of void *, therefore no need to have an explicit
> casting.

ok


>> +static int f81504_check_baudrate(u32 baud, size_t *idx)
>> +{
>> +	size_t index;
>> +	u32 quot, rem;
>> +
>> +	for (index = 0; index < ARRAY_SIZE(baudrate_table); ++index)
>
> Post-increment is also okay.
>
>> {
>> +		/* Clock source must largeer than desire baudrate */
>> +		if (baud > baudrate_table[index])
>> +			continue;
>> +
>> +		quot = DIV_ROUND_CLOSEST(baudrate_table[index],
>> baud);
>
> So, how quot is used and is it possible to set, for example, baud rate
> as 1000000 or 576000?

The IC don't support B1000000 due to no 16MHz clock source.

The quot & rem is only use for compare, and it's must be not 0
when the code run to calculate DIV_ROUND_CLOSEST. So quot
is a redundancy here.

This function will find the suitable clock source for future use.
We'll pass suitable baud rate * 16 to port->uartclk for
serial8250_do_set_termios() to do advance divider operations.

I'll rewrite this section with remove quot and direct check
the "baudrate_table[index] % baud" divisible.


>> +	u8 tmp, *offset = (u8 *) port->private_data;
>
> Same for provate_data as above.

ok


>> +			/*
>> +			 * direct use 1.8432MHz when baudrate
>> smaller then or
>> +			 * equal 115200bps
>
> Check your style of comments in a _whole_ your series.

ok


>> +			/*
>> +			 * If it can't found suitable clock source
>> but had old
>> +			 * accpetable baudrate, we'll use it
>
> Typo: acceptable.
> Baudrate ->  baud rate.

ok

>> +	port.port.private_data = data;	/* save current idx */
>
> Not sure you need to allocate memory for that at all, or maybe use a
> struct with one member (for now).
>

We just pass the index of PCI configuration space currently. So
I just set a allocated u8 memory to private data. We'll maintain
current method.


>> +static SIMPLE_DEV_PM_OPS(f81504_serial_pm_ops,
>> f81504_serial_suspend,
>> +		f81504_serial_resume);
>> +
>> +static struct platform_driver f81504_serial_driver = {
>> +	.driver = {
>> +		.name	= F81504_SERIAL_NAME,
>> +		.owner	= THIS_MODULE,
>
> You perhaps don't need this. Check the rest of the modules.

ok


>> +config SERIAL_8250_F81504
>> +        tristate "Fintek F81504/508/512 16550 PCIE device support"
>> if EXPERT
>> +        depends on SERIAL_8250 && MFD_FINTEK_F81504_CORE
>> +        default SERIAL_8250
>> +        select RATIONAL
>
> It seems RATIONAL API is not used here.
>

This driver hadn't use RATIONAL API. I'll remove it.


Thanks for your advice.
-- 
With Best Regards,
Peter Hung