Karmic fsl-imx51 SRU: only export NEON flag to userspace on Freescale iMX51 rev3.x or later silicon

[Amit Kucheria]

On 10 Feb 13, Andy Whitcroft wrote:
> On Thu, Feb 11, 2010 at 02:08:44PM -0700, Tim Gardner wrote:
> > The following changes since commit 4b1196706272826e74e35e9ebf2cc94ba8d4062c:
> >   Leann Ogasawara (1):
> >         UBUNTU: Ubuntu-2.6.31-108.21
> > 
> > are available in the git repository at:
> > 
> >   git://kernel.ubuntu.com/rtg/ubuntu-karmic fsl-imx51-neon
> > 
> > Bryan Wu (1):
> >       UBUNTU: SAUCE: IMX51: only export NEON flag to userspace on Freescale iMX51 rev3.x or later silicon
> > 
> >  arch/arm/vfp/vfpmodule.c |    7 ++++++-
> >  1 files changed, 6 insertions(+), 1 deletions(-)
> > 
> > From d77e3635c6d402cebdda49f654402c67460acfab Mon Sep 17 00:00:00 2001
> > From: Bryan Wu <bryan.wu at canonical.com>
> > Date: Tue, 26 Jan 2010 19:00:22 +0000
> > Subject: [PATCH] UBUNTU: SAUCE: IMX51: only export NEON flag to userspace on Freescale iMX51 rev3.x or later silicon
> > 
> > BugLink: http://bugs.launchpad.net/bugs/507416
> > 
> > NEON function is broken on old Freescale iMX51 silicons, such as rev1.x and
> > rev2.x. Since more and more iMX51 based products will move to rev3.x or later
> > silicon, we need to enable NEON on these newer silicons and disable NEON on
> > those old ones.
> > 
> > This patch will detect the silicon revision dynamically and only export NEON
> > flag to userspace on Freescale iMX51 rev3.x or later silicon. It was tested on
> > Babbage 3.0 board and Babbage 2.x board.
> > 
> > Signed-off-by: Bryan Wu <bryan.wu at canonical.com>
> > Signed-off-by: Andy Whitcroft <apw at canonical.com>
> > Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
> > ---
> >  arch/arm/vfp/vfpmodule.c |    7 ++++++-
> >  1 files changed, 6 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
> > index 2d7423a..e0d6b01 100644
> > --- a/arch/arm/vfp/vfpmodule.c
> > +++ b/arch/arm/vfp/vfpmodule.c
> > @@ -432,6 +432,10 @@ out:
> >  
> >  #include <linux/smp.h>
> >  
> > +#if defined(CONFIG_ARCH_MX51) && defined(CONFIG_NEON)
> > +#include <mach/hardware.h>
> > +#endif
> > +
> >  /*
> >   * VFP support code initialisation.
> >   */
> > @@ -498,7 +502,8 @@ static int __init vfp_init(void)
> >  		 * load/store instructions, integer and single
> >  		 * precision floating point operations.
> >  		 */
> > -		if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
> > +		if (((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
> > +			&& cpu_is_mx51_rev(CHIP_REV_3_0) > 0)
> >  			elf_hwcap |= HWCAP_NEON;
> >  #endif
> 
> Although this looks perfectly good for the fsl-imx51 branch, this
> appears wrong for non-imx51 use.  I think we should be programming with
> a view to this being merged into mainline at some point and not be
> adding anything which makes that harder.  Something more like this (with
> the appropriate incantation in the first stanza):
> 
>  && (!IMX51 || cpu_is_mx51_rev(CHIP_REV_3_0) > 0)

All this code is getting thrown away for upstreaming. Even the functions
prototypes to check for cpu revisions are different.

But you're right about the the general coding guidelines.

/Amit

-- 
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Amit Kucheria, Kernel Engineer || amit.kucheria at canonical.com
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