linux-kernel - Re: [PATCH] ARM: hw_breakpoint: Clear breakpoints before enabling monitor mode

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Message-ID: <20120924171934.GE5522@mudshark.cambridge.arm.com>
Date:	Mon, 24 Sep 2012 18:19:35 +0100
From:	Will Deacon <will.deacon@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: hw_breakpoint: Clear breakpoints before enabling
 monitor mode

On Thu, Sep 20, 2012 at 06:35:56PM +0100, Will Deacon wrote:
> On Thu, Sep 20, 2012 at 05:57:40PM +0100, Stephen Boyd wrote:
> > +/* Determine if halting mode is enabled */
> > +static int halting_mode_enabled(void)
> > +{
> > +	u32 dscr;
> > +
> > +	ARM_DBG_READ(c1, 0, dscr);
> > +
> > +	if (WARN_ONCE(dscr & ARM_DSCR_HDBGEN,
> > +		"halting debug mode enabled. Unable to access hardware resources.\n")) {
> > +		return -EPERM;
> > +	}
> > +	return 0;
> > +}
> 
> ...it looks like debug arch 7.1 defines this bit as UNKNOWN when the OS lock
> is clear, so we probably shouldn't be reading it at all. I'll pour myself a
> stiff drink and start reading the debug arch docs to work out what on Earth
> we should do.
> 
> Stay tuned.

Ok, I've pushed a bunch of patches to my hw-breakpoint branch (head commit
55cb726797c7). I'll post them to the list after the merge window, but please
do take them for a spin if you get a chance.

Will
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