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

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 22 August 2013 19:49, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> 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.

Ok. So we need U-boot to boot Xen on the fast model.

>
>> > 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.

It's not on my priority list :). I would be happy if someone work on this item.

>>
>> > 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. */
>> >
>>
>>
>
>



-- 
Julien Grall

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