Re: [Qemu-devel] Re: [PATCH 2/2] 8250: Customized base baudrate

[andrzej zaborowski]

On 14/04/2008, Jan Kiszka <address@hidden> wrote:
> andrzej zaborowski wrote:
>  > On 13/04/2008, Jan Kiszka <address@hidden> wrote:
>
> >>  --- a/hw/omap1.c
>  >>  +++ b/hw/omap1.c
>  >>  @@ -1734,7 +1734,8 @@ struct omap_uart_s *omap_uart_init(targe
>  >>      struct omap_uart_s *s = (struct omap_uart_s *)
>  >>              qemu_mallocz(sizeof(struct omap_uart_s));
>  >>      if (chr)
>  >>  -        s->serial = serial_mm_init(base, 2, irq, chr, 1);
>  >>  +        s->serial =
>  >>  +            serial_mm_init(base, 2, irq, omap_clk_getrate(clk)/16, chr, 
> 1);
>  >
>  > Yes, this should be correct.
>
> While typing those line I wondered if it is possible and reasonable that
>  a guest changes this clock rate during runtime? In that case, the
>  perfect, but probably much more complex solution would be to track those
>  changes also with the serial emulation...

Yes, UART1 and UART3 (I think) can switch between 48MHz (dpll) and
16MHz clock domains on OMAP1 and the guest has control over this (and
the characters flow indeed slows down three times when you switch to
16MHz on the real hw).  omap_clk.c allows a peripheral to register for
notifications of rate change for a particular clock. I don't think
it's worth bothering too much because anything that depends on the
timing of QEMU will likely have problems anyway.

Regards
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