linux-kernel - Re: [PATCH v4 2/5] arm: add new asm macro update

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Message-ID: <20140203165718.GO14112@mudshark.cambridge.arm.com>
Date:	Mon, 3 Feb 2014 16:57:18 +0000
From:	Will Deacon <will.deacon@....com>
To:	Leif Lindholm <leif.lindholm@...aro.org>
Cc:	"msalter@...hat.com" <msalter@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"patches@...aro.org" <patches@...aro.org>,
	"roy.franz@...aro.org" <roy.franz@...aro.org>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 2/5] arm: add new asm macro update_sctlr

On Mon, Feb 03, 2014 at 04:46:36PM +0000, Leif Lindholm wrote:
> On Mon, Feb 03, 2014 at 04:00:51PM +0000, Will Deacon wrote:
> > > > > With the two call sites in uefi_phys.S as:
> > > > > 
> > > > > 	ldr	r5, =(CR_M)
> > > > > 	update_sctlr	r12, , r5
> > > > > and
> > > > > 	ldr	r4, =(CR_I | CR_C | CR_M)
> > > > > 	update_sctlr	r12, r4
> > > > 
> > > > These ldr= could be movs, right?
> > > 
> > > The first one could.
> > > The second one could be movw on armv7+.
> > > 
> > > > If so, I definitely prefer this to putting an ldr = into the macro itself
> > > > (option 2).
> > > 
> > > And your preference between 1) and 2) is?
> > 
> > (1), using bic and mov[tw] where possible.
> 
> (1): ok, thanks.
> 
> bic: sure, that was an oversight.
> 
> mov[tw]: why?
> Then we end up battling different available immediate fields in A32/T32
> instruction sets and v5/v6/v7 architecture versions.

I was making the assumption that UEFI was going to be v7 only... is this not
true?

Will
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