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

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Message-ID: <4B4C4B86.7090509@LiPPERTEmbedded.de>
Date:	Tue, 12 Jan 2010 11:14:30 +0100
From:	Jens Rottmann <JRottmann@...PERTEmbedded.de>
To:	Andres Salomon <dilinger@...labora.co.uk>
CC:	linux-kernel@...r.kernel.org, linux-geode@...badil.infradead.org
Subject: [PATCH] geode-mfgpt: restore previous behavior for selecting IRQ

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@...PERTEmbedded.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.

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?

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.");

_

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