Re: [Xen-devel] [PATCH] pl011: early_panic if baud rate not set in hardware

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-08-22 at 17:34 +0100, Julien Grall wrote:
> On 08/22/2013 05:01 PM, Ian Campbell wrote:
> > Now that the driver defaults to BAUD_AUTO this can happen if the early uart 
> > !=
> > console or if early printk isn't in use.
> 
> Does the fast model set correctly the baud rate?

No.

> > The following division by zero causes a trap but that uses regular printk 
> > and
> > not early_printk, so it is never seen.
> 
> That's annoying. I often have this problem, is there any plan to support
> early print in printk?

TBH I thought it was somewhere (far down) your todo list. Maybe I'll
have a poke at it tomorrow.

> 
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > ---
> >  xen/drivers/char/pl011.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > diff --git a/xen/drivers/char/pl011.c b/xen/drivers/char/pl011.c
> > index 0e1eb64..7eb90b0 100644
> > --- a/xen/drivers/char/pl011.c
> > +++ b/xen/drivers/char/pl011.c
> > @@ -104,6 +104,8 @@ static void __init pl011_init_preirq(struct serial_port 
> > *port)
> >      {
> >          /* Baud rate already set: read it out from the divisor latch. */
> >          divisor = (pl011_read(uart, IBRD) << 6) | (pl011_read(uart, FBRD));
> > +        if (!divisor)
> > +            early_panic("pl011: No Baud rate configured\n");
> >          uart->baud = (uart->clock_hz << 2) / divisor;
> >      }
> >      /* This write must follow FBRD and IBRD writes. */
> > 
> 
> 



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