Re: [PATCH] geode-mfgpt: restore previous behavior for selecting IRQ

Andres Salomon
2010-01-18T15:34:37Z

On Tue, 12 Jan 2010 11:14:30 +0100
Jens Rottmann <JRottmann@LiPPERTEmbedded.de> wrote:

> geode-mfgpt: restore previous behavior for selecting IRQ
>
> The MFGPT IRQ used to be, in order of decreasing priority,
> * IRQ supplied by the user as a boot-time parameter,
> * IRQ previously set by the BIOS or another driver,
> * default IRQ given at compile time.
>
> Return to this behavior, which got broken when splitting the
> MFGPT/clocksource driver for 2.6.33-rc1.
>
> Signed-off-by: Jens Rottmann <JRottmann@LiPPERTEmbedded.de>
> ---
>
> Hi Andres,
>
> a bit more detail. Up to 2.6.32 the MFGPT IRQ was chosen like this:
>
> static int irq;
> static int __init mfgpt_setup(char *str)
> {
> get_option(&str, &irq);
> return 1;
> }
> __setup("mfgpt_irq=", mfgpt_setup);
> [...]
> /* Choose IRQ: if none supplied, keep IRQ already set or use default
> */ if (!*irq)
> *irq = (zsel >> shift) & 0xF; // may have been set by
> the BIOS if (!*irq)
> *irq = MFGPT_DEFAULT_IRQ; // #defined as 7
>
> The code in 2.6.33-rc3 after the MFGPT/clocksource split looks like
> this:
>
> static int timer_irq = CONFIG_CS5535_MFGPT_DEFAULT_IRQ; //
> defaults to 7 module_param_named(irq, timer_irq, int, 0644);
> [...]
> if (!*irq)
> *irq = (zsel >> shift) & 0xF; // gets ignored
> now if (!*irq)
> *irq = CONFIG_CS5535_MFGPT_DEFAULT_IRQ; // again!?
>
> The patch removes the first of the two ocurrances of
> CONFIG_CS5535_MFGPT_DEFAULT_IRQ, reverting the IRQ selection to the
> previous (working) behavior.

You're right, thanks. For the patch below:

Acked-by: Andres Salomon <dilinger@collabora.co.uk>

>
>
> BTW, while looking into this I stumbled upon the fact that
> cs5535_mfgpt_init() doesn't free up the timer in the error path if
> cs5535_mfgpt_setup_irq() or setup_irq() fail. However, some comments
> in cs5535-mfgpt.c (stating that it's not possible to release the
> individual timer hardware) make me think this might have been skipped
> on purpose? Could you please have a look?

Oh, you mean in the clockevt driver? Yeah, we can't really free the
timer, unfortunately.

It actually might not be a bad idea to reverse the code so that the IRQ
allocation happens first, since we can clean that up if mfgpt
allocation fails. Feel like sending a patch? :)

>
> Thanks,
> Jens
>
> --- linux-2.6.33-rc3-git4/drivers/clocksource/cs5535-clockevt.c
> +++ previous_behavior/drivers/clocksource/cs5535-clockevt.c
> @@ -21,7 +21,7 @@
>
> #define DRV_NAME "cs5535-clockevt"
>
> -static int timer_irq = CONFIG_CS5535_MFGPT_DEFAULT_IRQ;
> +static int timer_irq;
> module_param_named(irq, timer_irq, int, 0644);
> MODULE_PARM_DESC(irq, "Which IRQ to use for the clock source MFGPT
> ticks.");
> _
>