On Tue, 2018-07-03 at 10:22 +0800, Jisheng Zhang wrote:
> Hi,
>
> On Mon, 2 Jul 2018 14:51:03 +0300 Andy Shevchenko wrote:
>
> > On Mon, 2018-07-02 at 13:18 +0300, Andy Shevchenko wrote:
> > > On Mon, 2018-07-02 at 18:04 +0800, Jisheng Zhang wrote:
> > > > For Synopsys DesignWare 8250 uart which version >= 4.00a,
> > > > there's a
> > > > valid divisor latch fraction register. The fractional divisor
> > > > width
> > > > is
> > > > 4bits ~ 6bits.
> > > >
> > >
> > > There are several serial IPs that have fractional divider built-
> > > in.
> > > None
> > > is using any specific hooks. Why do you need in your case, esp.
> > > taking
> > > into consideration that we have a custom ->set_termios()
> > > callback?
> >
> > Okay, I see that in 8250 we have hooks embedded into 8250_port.c
> > which
> > is not the best solution.
> >
> > For example it prevents better splitting Exar code.
> > So, we would need these hooks, but better to integrate them in the
> > same
> > way like it's done for the rest of 8250 ones, i.e.
> > - rename existing to have a "do" word
> > - create new functions which would be a replacement that choose
> > between
> > "do" variant and custom one
> > - not sure if we need to export "do" variants (at least for now)
>
> So you mean add the support as following:
>
> 1.rename current serial8250_set_divisor as serial8250_do_set_divisor
>
Yes
> 2.add a new serial8250_set_divisor which will be as simple as
Yes and no.
>
> static void serial8250_set_divisor(struct uart_port *port, ...)
> {
> struct uart_8250_port *up = up_to_u8250p(port);
>
> if (up->set_divisor)
port->
> up->set_divisor(...);
port->
> else
> serial8250_do_set_divisor(...);
> }
>
> could you please confirm?
Yes.
>
> Another issue is I'm not sure which struct to add the hook,
> struct uart_port or struct uart_8250_port? Currently, it seems that
> only
> uart_8250_port needs this hook,
Define "needs". 8250 _uses_ it, the rest which I easy grepped would be
able to use it if we provide such a possibility.
lantiq.c is one example (currently they don't use it), or
drivers/tty/serial/digicolor-usart.c limits baud rate choice b/c of
absence of a common way.
> sure, adding the hook to struct uart_port
> is fine either. Could you please kindly give some suggestions?
See above. Thanks for doing this!
>
> Thanks,
> Jisheng
--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Intel Finland Oy
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