linux-kernel - [PATCH] cs5535-mfgpt: reuse timers that have never been set up

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Date:	Thu, 08 Jul 2010 17:04:38 +0200
From:	Jens Rottmann <JRottmann@...PERTEmbedded.de>
To:	Andres Salomon <dilinger@...labora.co.uk>
CC:	Jordan Crouse <jordan@...micpenguin.net>,
	linux-geode@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] cs5535-mfgpt: reuse timers that have never been set up

cs5535-mfgpt: reuse timers that have never been set up

The MFGPT hardware may be set up only once, therefore cs5535_mfgpt_free_timer()
didn't re-set the timer's "avail" bit.  However if a timer is freed before it
has actually been in use then it may be made available again.

Signed-off-by: Jens Rottmann <JRottmann@...PERTEmbedded.de>
---

Hi Andres,

Jens wrote:
> Andres wrote:
>> Jens wrote:
>>> cs5535_mfgpt_init() doesn't free up the timer in the error path
>>
>> 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.
>
> [...] I guess for reversing the order we'd have to split both
> cs5535_mfgpt_alloc_timer() and cs5535_mfgpt_setup_irq() into two parts [...]
> Maybe cs5535_mfgpt_free_timer() can be made more intelligent to set
> mfgpt->avail again if the hardware isn't actually in a non-reversible state
> yet [...]

As you can see I did just that. What do you think?

Cheers,
Jens

--- linux-2.6.35-rc4/drivers/misc/cs5535-mfgpt.c
+++ mfgpt_reuse_timers/drivers/misc/cs5535-mfgpt.c
@@ -211,6 +211,17 @@
  */
 void cs5535_mfgpt_free_timer(struct cs5535_mfgpt_timer *timer)
 {
+	unsigned long flags;
+	uint16_t val;
+
+	/* timer can be made available again only if never set up */
+	val = cs5535_mfgpt_read(timer, MFGPT_REG_SETUP);
+	if (!(val & MFGPT_SETUP_SETUP)) {
+		spin_lock_irqsave(&timer->chip->lock, flags);
+		__set_bit(timer->nr, timer->chip->avail);
+		spin_unlock_irqrestore(&timer->chip->lock, flags);
+	}
+
 	kfree(timer);
 }
 EXPORT_SYMBOL_GPL(cs5535_mfgpt_free_timer);
_

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