[PATCH linux dev-4.13] serial: 8250: Add Nuvoton NPCM UART

[Avi Fishman]

On Tue, Feb 6, 2018 at 7:50 AM, Joel Stanley <joel at jms.id.au> wrote:
> On Mon, Feb 5, 2018 at 7:39 PM, Tomer Maimon <tmaimon77 at gmail.com> wrote:
>> On 2 February 2018 at 06:27, Joel Stanley <joel at jms.id.au> wrote:
>
>>>  /* Uart divisor latch read */
>>> @@ -2143,6 +2153,15 @@ int serial8250_do_startup(struct uart_port *port)
>>>                                 UART_DA830_PWREMU_MGMT_FREE);
>>>         }
>>>
>>> +       if (port->type == PORT_NPCM) {
>>> +               /*
>>> +                * Nuvoton calls the scratch register 'UART_TOR' (timeout
>>> +                * register). Enable it, and set TIOC (timeout interrupt
>>> +                * comparator) to be 0x20 for correct operation.
>>> +                */
>>> +               serial_port_out(port, UART_NPCM_TOR, UART_NPCM_TOIE | 0x20);
>>> +       }
>>
>> Can we set the TOR register dynamically (adding special IOCTL)?
>
> We would have to have a good reason to do so.
>
> Under what circumstances would a user need to change this dynamically?

Tomer, I agree it is not important to change at run time.

>
>>
>>> +
>>>  #ifdef CONFIG_SERIAL_8250_RSA
>>>         /*
>>>          * If this is an RSA port, see if we can kick it up to the
>>> @@ -2465,6 +2484,15 @@ static unsigned int xr17v35x_get_divisor(struct uart_8250_port *up,
>>>         return quot_16 >> 4;
>>>  }
>>>
>>> +/* Nuvoton NPCM UARTs have a custom divisor calculation */
>>> +static unsigned int npcm_get_divisor(struct uart_8250_port *up,
>>> +               unsigned int baud)
>>> +{
>>> +       struct uart_port *port = &up->port;
>>> +
>>> +       return DIV_ROUND_CLOSEST(port->uartclk, 16 * baud + 2) - 2;
>>> +}
>
> Did you test this version of the driver on your hardware?
>
> I think I understand why you had the extra code, but does it affect
> operation in any of your tests?
>
> From what I understand the baud rates are often calculated to be "near enough".

Joel, I made the original calculation but I agree that this one is
good enough (I confused Tomer to think that your calculation will not
fit :)

>
> Cheers,
>
> Joel