RE: [PATCH v1 tty-next 1/2] 8250: microchip: pci1xxxx: Add driver for the quad-uart function in the multi-function endpoint of pci1xxxx device.

[Kumaravel.Thiagarajan]

> -----Original Message-----
> From: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> Sent: Thursday, September 1, 2022 7:12 PM
> To: Kumaravel Thiagarajan - I21417 <Kumaravel.Thiagarajan@xxxxxxxxxxxxx>
> Cc: andy.shevchenko@xxxxxxxxx; Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx>; Jiri Slaby <jirislaby@xxxxxxxxxx>; u.kleine-
> koenig@xxxxxxxxxxxxxx; johan@xxxxxxxxxx; wander@xxxxxxxxxx;
> etremblay@xxxxxxxxxxxxxxxxxxxx; macro@xxxxxxxxxxx;
> geert+renesas@xxxxxxxxx; jk@xxxxxxxxxx; phil.edworthy@xxxxxxxxxxx;
> Lukas Wunner <lukas@xxxxxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>;
> linux-serial <linux-serial@xxxxxxxxxxxxxxx>; UNGLinuxDriver
> <UNGLinuxDriver@xxxxxxxxxxxxx>
> Subject: RE: [PATCH v1 tty-next 1/2] 8250: microchip: pci1xxxx: Add driver for
> the quad-uart function in the multi-function endpoint of pci1xxxx device.
> 
> 
> On Thu, 1 Sep 2022, Kumaravel.Thiagarajan@xxxxxxxxxxxxx wrote:
> 
> > > > +       const unsigned int standard_baud_list[] = {50, 75, 110, 134, 150,
> 300,
> > > > +                                               600, 1200, 1800, 2000, 2400, 3600,
> > > > +                                               4800, 7200, 9600, 19200, 38400, 57600,
> > > > +                                               115200, 125000, 136400, 150000, 166700,
> > > > +                                               187500, 214300, 250000, 300000, 375000,
> > > > +                                               500000, 750000,
> > > > + 1000000, 1500000};
> > >
> > > Why?!
> >
> > The standard baud rates are handled within serial8250_do_set_termios
> > which is invoked from within mchp_pci1xxxx_set_termios in first place.
> > Hence if it matches with any of the standard baudrates, it can return
> > immediately.
> 
> Care to explain why the baudrates in your table don't match those in
> tty_baudrate.c? ...It makes no sense to me that you call these "standard
> baud rates".
The baudrates in my table are from our legacy UART IP and these baudrates can be
generated by the hardware by updating UART_DLL & UART_DLM alone as done by the
serial8250_do_set_termios.
I noticed that some of the baud rates in tty_baudrate.c arenot listed in this table
but will still be handled by the mchp_pci1xxxx_set_termios.
I can rename standard_baud_list to simply baud_list. Please let me know.

Thank You.

Regards,
Kumaravel