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

[Chen Baozi <baozich@xxxxxxxxx>]

On Aug 23, 2013, at 5:09 AM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

> 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.

Some one posted a ARM64 support for fast model on u-boot recently.

See: http://lists.denx.de/pipermail/u-boot/2013-August/161120.html

Hope it would be helpful.

Cheers,

Baozi

> 
>> 
>>>> 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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> http://lists.xen.org/xen-devel


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