[PATCH 1/1] microblaze: Added fdt chosen capability for timer

[John Williams]

On Thu, Nov 10, 2011 at 11:10 PM, Michal Simek <monstr at monstr.eu> wrote:
> From: "Peter A. G. Crosthwaite" <peter.crosthwaite at petalogix.com>
>
> This lets a dts author flag a particular timer in the system as the system timer.
> If the chosen node contains a "system-timer=<&foo>" entry than that handle will
> be used to determine the system timer. In no such entry exists then the first
> found timer will be used (current behaviour).
>
> Signed-off-by: Peter A. G. Crosthwaite <peter.crosthwaite at petalogix.com>
> Signed-off-by: Michal Simek <monstr at monstr.eu>
> ---
>  arch/microblaze/kernel/timer.c |   12 ++++++++----
>  1 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/arch/microblaze/kernel/timer.c b/arch/microblaze/kernel/timer.c
> index 91804cd..c289412 100644
> --- a/arch/microblaze/kernel/timer.c
> +++ b/arch/microblaze/kernel/timer.c
> @@ -267,11 +267,15 @@ void __init time_init(void)
>                NULL
>        };
>
> -       for (i = 0; timer_list[i] != NULL; i++) {
> +       prop = of_get_property(of_chosen, "system-timer", NULL);
> +       if (prop)
> +               timer = of_find_node_by_phandle(be32_to_cpup(prop));

Suggest expanding this code to check that the chosen timer meets the
kernel requirements - IRQ connected, dual channel etc.

If it fails, then perhaps fall through to finding the first suitable
one, or panic()?

> +       else
> +               printk(KERN_INFO "No chosen timer found, using default\n");
> +
> +       for (i = 0; timer_list[i] != NULL && !timer; i++)
>                timer = of_find_compatible_node(NULL, NULL, timer_list[i]);
> -               if (timer)
> -                       break;

There is another issue I think - can we somehow mark the system timer
instance as 'taken' so it can't be bound by another driver that might
be compatible (esp. generic-uio for example).

Currently if you mark the timer as generic-uio then a UIO app can mess
with it - not good.

John
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