* Tony Lindgren <tony@xxxxxxxxxxx> [100622 16:15]:
> * Catalin Marinas <catalin.marinas@xxxxxxx> [100622 15:53]:
> > On Mon, 2010-06-21 at 14:51 +0100, Tony Lindgren wrote:
> > > diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
> > > index 315a540..19ba626 100644
> > > --- a/arch/arm/vfp/vfpmodule.c
> > > +++ b/arch/arm/vfp/vfpmodule.c
> > > @@ -549,10 +549,14 @@ static int __init vfp_init(void)
> > > /*
> > > * Check for the presence of the Advanced SIMD
> > > * load/store instructions, integer and single
> > > - * precision floating point operations.
> > > + * precision floating point operations. Only check
> > > + * for NEON if the hardware has TLS register as the
> > > + * MVFR registers got added in ARM1136 r1p0 with TLS.
> > > */
> > > - if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
> > > - elf_hwcap |= HWCAP_NEON;
> > > + if (elf_hwcap & HWCAP_TLS) {
> > > + if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
> > > + elf_hwcap |= HWCAP_NEON;
> > > + }
> >
> > MVFR should be available with the new CPU id format:
> >
> > ((read_cpuid_id() & 0x000f0000) == 0x000f0000)
> >
> > I think that would be a cleaner test than relying on the TLS presence.
>
> OK, thanks that's better. Will update accordingly and repost.
Here's this one updated. Using your better MVFR check also removes the
dependency to the previous patch.
Regards,
Tony
From: Tony Lindgren <tony@xxxxxxxxxxx>
Date: Mon, 21 Jun 2010 16:33:28 +0300
Subject: [PATCH] arm: Make VFPv3 usable on ARMv6
MVFR0 and MVFR1 are only available starting with ARM1136 r1p0 release
according to "B.5 VFP changes" in DDI0211F_arm1136_r1p0_trm.pdf. This is
also when TLS register got added, so we can use HAS_TLS also to test for
MVFR0 and MVFR1.
Otherwise VFPFMRX and VFPFMXR access fails and we get:
Internal error: Oops - undefined instruction: 0 [#1]
PC is at no_old_VFP_process+0x8/0x3c
LR is at __und_svc+0x48/0x80
...
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h
index 422f3cc..3d5fc41 100644
--- a/arch/arm/include/asm/vfpmacros.h
+++ b/arch/arm/include/asm/vfpmacros.h
@@ -3,6 +3,8 @@
*
* Assembler-only file containing VFP macros and register definitions.
*/
+#include <asm/hwcap.h>
+
#include "vfp.h"
@ Macros to allow building with old toolkits (with no VFP support)
@@ -22,12 +24,20 @@
LDC p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d0-d15}
#endif
#ifdef CONFIG_VFPv3
+#if __LINUX_ARM_ARCH__ <= 6
+ ldr \tmp, =elf_hwcap @ may not have MVFR regs
+ ldr \tmp, [\tmp, #0]
+ tst \tmp, #HWCAP_VFPv3D16
+ ldceq p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31}
+ addne \base, \base, #32*4 @ step over unused register space
+#else
VFPFMRX \tmp, MVFR0 @ Media and VFP Feature Register 0
and \tmp, \tmp, #MVFR0_A_SIMD_MASK @ A_SIMD field
cmp \tmp, #2 @ 32 x 64bit registers?
ldceql p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register space
#endif
+#endif
.endm
@ write all the working registers out of the VFP
@@ -38,10 +48,18 @@
STC p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d0-d15}
#endif
#ifdef CONFIG_VFPv3
+#if __LINUX_ARM_ARCH__ <= 6
+ ldr \tmp, =elf_hwcap @ may not have MVFR regs
+ ldr \tmp, [\tmp, #0]
+ tst \tmp, #HWCAP_VFPv3D16
+ stceq p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31}
+ addne \base, \base, #32*4 @ step over unused register space
+#else
VFPFMRX \tmp, MVFR0 @ Media and VFP Feature Register 0
and \tmp, \tmp, #MVFR0_A_SIMD_MASK @ A_SIMD field
cmp \tmp, #2 @ 32 x 64bit registers?
stceql p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register space
#endif
+#endif
.endm
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 315a540..8063a32 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -15,6 +15,7 @@
#include <linux/sched.h>
#include <linux/init.h>
+#include <asm/cputype.h>
#include <asm/thread_notify.h>
#include <asm/vfp.h>
@@ -549,10 +550,13 @@ static int __init vfp_init(void)
/*
* Check for the presence of the Advanced SIMD
* load/store instructions, integer and single
- * precision floating point operations.
+ * precision floating point operations. Only check
+ * for NEON if the hardware has the MVFR registers.
*/
- if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
- elf_hwcap |= HWCAP_NEON;
+ if ((read_cpuid_id() & 0x000f0000) == 0x000f0000) {
+ if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
+ elf_hwcap |= HWCAP_NEON;
+ }
#endif
}
return 0;
