linux-kernel - Re: [PATCH] atmel_serial: Split the interrupt handler

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Message-ID: <20071218181921.2478baa9@dhcp-252-066.norway.atmel.com>
Date:	Tue, 18 Dec 2007 18:19:21 +0100
From:	Haavard Skinnemoen <hskinnemoen@...el.com>
To:	"Remy Bohmer" <linux@...mer.net>
Cc:	"Andrew Victor" <linux@...im.org.za>,
	"ARM Linux Mailing List" <linux-arm-kernel@...ts.arm.linux.org.uk>,
	"Russell King - ARM Linux" <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] atmel_serial: Split the interrupt handler

Crud...my mailer helpfully filtered this into the huge linux-kernel
bin instead of leaving it in my inbox...

On Tue, 18 Dec 2007 16:23:11 +0100
"Remy Bohmer" <linux@...mer.net> wrote:

> Hello Haavard,
> 
> A few remarks:
> 
> > From: Remy Bohmer <hskinnemoen@...el.com>
> 
> My name, at your address ;-)))

Right. Wonder how that happened...I'll try to fix it manually before I
send the next patchbomb.

> > This patch splits up the interrupt handler of the serial port
> > into a interrupt top-half and a tasklet.
> 
> I see you moved the handling of the sysrq-key to the tasklet. This was
> actually a very nice feature in the IRQ-top half on preempt-RT. This
> helps debugging running away RT-processes.

Ah. Good point. I guess we should move it back, then.

> > In this version of the patch, we try to only do things that are
> > absolutely necessary in the interrupt handler, storing away the
> > status register along with the received character and letting the
> > tasklet handle break, sysrq, error flags, etc.
> 
> Preempt-RT now absolutely requires my (4th) IRQ_NODELAY patch, because
> the spinlock now is always inside the code, and not only in
> theexception path, and thus without my NO_DELAY patch we have a panic
> during boot.
> On preempt-RT this spinlock must be a raw-spinlock. (If this type is
> known in the mainline kernel, you can apply that patch it anyway)

I'll see if that works.

> BTW: Attached I have added a 2nd patch that I use for Preempt-RT. (For
> cleaner startup, and to get rid of useless IRQ-threads.

Hrm. That assumption isn't valid on AVR32...on AP7000, for example,
IRQ1 is used by the LCD controller.

> > This patch should apply on top of the cleanup patch I sent earlier
> 
> For the cleanup patch:
> Acked-by: Remy Bohmer <linux@...mer.net>
> 
> > today. Or at least I think so...I'll send the full series once
> > everyone are happy.
> 
> So, for this patch: I am almost happy ;-)

Great :-)

Haavard
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