linux-kernel - RE: [RFC/PATCH 2/4] input: misc: twl4030: move to request_threaded

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Date:	Mon, 14 Dec 2009 17:01:11 +0530
From:	"Shilimkar, Santosh" <santosh.shilimkar@...com>
To:	Felipe Balbi <felipe.balbi@...ia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>,
	Aaro Koskinen <aaro.koskinen@...ia.com>,
	David Brownell <david-b@...bell.net>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	Anton Vorontsov <avorontsov@...mvista.com>,
	Grazvydas Ignotas <notasas@...il.com>,
	"Chikkature Rajashekar, Madhusudhan" <madhu.cr@...com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Samuel Ortiz <sameo@...nedhand.com>
Subject: RE: [RFC/PATCH 2/4] input: misc: twl4030: move to
 request_threaded_irq

Felipe,
> -----Original Message-----
> From: linux-omap-owner@...r.kernel.org [mailto:linux-omap-owner@...r.kernel.org] On Behalf Of Felipe
> Balbi
> Sent: Monday, December 14, 2009 4:01 PM
> To: linux-kernel@...r.kernel.org
> Cc: Linux OMAP Mailing List; Tony Lindgren; Aaro Koskinen; David Brownell; Linux USB Mailing List;
> Anton Vorontsov; Grazvydas Ignotas; Chikkature Rajashekar, Madhusudhan; Greg Kroah-Hartman; Mark
> Brown; Samuel Ortiz; Felipe Balbi
> Subject: [RFC/PATCH 2/4] input: misc: twl4030: move to request_threaded_irq
> 
> move to request_threaded_irq() on twl4030 children.
> 
> Signed-off-by: Felipe Balbi <felipe.balbi@...ia.com>
> ---
>  drivers/input/misc/twl4030-pwrbutton.c |   12 +-----------
>  1 files changed, 1 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/input/misc/twl4030-pwrbutton.c b/drivers/input/misc/twl4030-pwrbutton.c
> index f5fc997..cd47d9e 100644
> --- a/drivers/input/misc/twl4030-pwrbutton.c
> +++ b/drivers/input/misc/twl4030-pwrbutton.c
> @@ -39,16 +39,6 @@ static irqreturn_t powerbutton_irq(int irq, void *_pwr)
>  	int err;
>  	u8 value;
> 
> -#ifdef CONFIG_LOCKDEP
> -	/* WORKAROUND for lockdep forcing IRQF_DISABLED on us, which
> -	 * we don't want and can't tolerate since this is a threaded
> -	 * IRQ and can sleep due to the i2c reads it has to issue.
> -	 * Although it might be friendlier not to borrow this thread
> -	 * context...
> -	 */
> -	local_irq_enable();
> -#endif
> -
>  	err = twl4030_i2c_read_u8(TWL4030_MODULE_PM_MASTER, &value,
>  				  STS_HW_CONDITIONS);
>  	if (!err)  {
> @@ -80,7 +70,7 @@ static int __devinit twl4030_pwrbutton_probe(struct platform_device *pdev)
>  	pwr->phys = "twl4030_pwrbutton/input0";
>  	pwr->dev.parent = &pdev->dev;
> 
> -	err = request_irq(irq, powerbutton_irq,
> +	err = request_threaded_irq(irq, NULL, powerbutton_irq,
>  			IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING,
>  			"twl4030_pwrbutton", pwr);
>  	if (err < 0) {
In whole of the series the ISR you have converted to threads using threaded_irq are very
small in size. They are like quick_change_handlers. So only advantage is the particular 
interrupt is masked for bit longer than with you change.

I might be wrong here but it might introduce the spurious IRQ's because of bit of delay in the processing.What is the motive for this change ? Are we using this API as it suppose to be ?
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