linux-kernel - Re: [PATCH 8/8] ARM: tegra: HACK: remove set_irq

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Message-ID: <20120301205408.GB19274@n2100.arm.linux.org.uk>
Date:	Thu, 1 Mar 2012 20:54:08 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Alan Ott <alan@...nal11.us>, Colin Cross <ccross@...roid.com>,
	Olof Johansson <olof@...om.net>,
	Stephen Warren <swarren@...dia.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lucas De Marchi <lucas.demarchi@...fusion.mobi>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 8/8] ARM: tegra: HACK: remove set_irq_flags() from
	driver

On Thu, Mar 01, 2012 at 09:33:03PM +0100, Linus Walleij wrote:
> On Thu, Mar 1, 2012 at 8:26 PM, Alan Ott <alan@...nal11.us> wrote:
> 
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > The driver should not call set_irq_flags itself, and
> > cannot do this from a loadable module.
> >
> > Remove the call for now, which might break the driver
> > but at least lets the kernel link again.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >  drivers/usb/host/ehci-tegra.c |    1 -
> >  1 files changed, 0 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c
> > index dbc7fe8..ab91f26 100644
> > --- a/drivers/usb/host/ehci-tegra.c
> > +++ b/drivers/usb/host/ehci-tegra.c
> > @@ -729,7 +729,6 @@ static int tegra_ehci_probe(struct platform_device *pdev)
> >                err = -ENODEV;
> >                goto fail;
> >        }
> > -       set_irq_flags(irq, IRQF_VALID);
> 
> The kernel is full of this kind of stuff (drivers/mfd/twl4030-irq.c):
> 
> #ifdef CONFIG_ARM
>         /* ARM requires an extra step to clear IRQ_NOREQUEST, which it
>          * sets on behalf of every irq_chip.  Also sets IRQ_NOPROBE.
>          */
>         set_irq_flags(irq, IRQF_VALID);
> #else
>         /* same effect on other architectures */
>         irq_set_noprobe(irq);
> #endif
> 
> Can't we try to fix this for real instead of breaking the universe,
> hehe :-)

That depends whether you want 0..NR_IRQS to all be request-able before
they've been setup with their irq chips and handlers etc.

Unfortunately, genirq doesn't provide a standard helper to clear
IRQ_NOREQUEST, and that's why this pain persists.
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