Re: [PATCH 6/8] [POWERPC] sysdev,qe_lib: implement FSL GTM support

[Laurent Pinchart <laurentp@cse-semaphore.com>]

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On Tuesday 11 March 2008 18:24, Anton Vorontsov wrote:
> GTM stands for General-purpose Timers Module and able to generate
> timer{1,2,3,4} interrupts.
> 
> There are several limitations in this support:
> 1. Cascaded (32 bit) timers unimplemented (1-2, 3-4).
>    This is straightforward to implement when needed, two timers should
>    be marked as "requested" and configured as appropriate.
> 2. Super-cascaded (64 bit) timers unimplemented (1-2-3-4).
>    This is also straightforward to implement when needed, all timers
>    should be marked as "requested" and configured as appropriate.
> 
> Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>

[snip]

> +void gtm_stop_timer_16(struct gtm_timer *tmr)
> +{
> +	struct gtm *gtm = tmr->gtm;
> +	int num = tmr - &gtm->timers[0];
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&gtm->lock, flags);
> +
> +	setbits8(tmr->gtcfr, GTCFR_STP(num));

Shouldn't we clear the timer events with

out_be16(tmr->gtevr, 0xFFFF);

here ? Otherwise the timer interrupt could still fire after the timer is 
stopped. This introduces a race condition in drivers that blindly re-arm the 
timer in the interrupt handler. I've been bitten by this while porting your 
FHCI USB driver to a CPM2 platform.

> +
> +	spin_unlock_irqrestore(&gtm->lock, flags);
> +}
> +EXPORT_SYMBOL(gtm_stop_timer_16);

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75

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