[PATCH] pl011: early_panic if baud rate not set in hardware

[PATCH] pl011: early_panic if baud rate not set in hardware

[Ian Campbell]

Now that the driver defaults to BAUD_AUTO this can happen if the early uart !=
console or if early printk isn't in use.

The following division by zero causes a trap but that uses regular printk and
not early_printk, so it is never seen.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
 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. */
-- 
1.7.2.5

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

[Julien Grall]

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?

> 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?

> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>
> ---
>  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

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

[Ian Campbell]

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@citrix.com>
> Acked-by: Julien Grall <julien.grall@linaro.org>
> > ---
> >  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. */
> > 
> 
> 

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

[Julien Grall]

On 22 August 2013 19:49, Ian Campbell <Ian.Campbell@citrix.com> 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@citrix.com>
>> Acked-by: Julien Grall <julien.grall@linaro.org>
>> > ---
>> >  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

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

[Chen Baozi]

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

> On 22 August 2013 19:49, Ian Campbell <Ian.Campbell@citrix.com> 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@citrix.com>
>>> Acked-by: Julien Grall <julien.grall@linaro.org>
>>>> ---
>>>> 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
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

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

[Ian Campbell]

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?
> 
> > 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?

I didn't get to this like I thought I might last week

> > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Acked-by: Julien Grall <julien.grall@linaro.org>

Applied, thanks.