Commit 39141ddf authored by Paul Walmsley's avatar Paul Walmsley Committed by Russell King
Browse files

ARM: 7566/1: vfp: fix save and restore when running on pre-VFPv3 and CONFIG_VFPv3 set

After commit 846a1368 ("ARM: vfp: fix
saving d16-d31 vfp registers on v6+ kernels"), the OMAP 2430SDP board
started crashing during boot with omap2plus_defconfig:

[    3.875122] mmcblk0: mmc0:e624 SD04G 3.69 GiB
[    3.915954]  mmcblk0: p1
[    4.086639] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
[    4.093719] Modules linked in:
[    4.096954] CPU: 0    Not tainted  (3.6.0-02232-g759e00b8 #570)
[    4.103149] PC is at vfp_reload_hw+0x1c/0x44
[    4.107666] LR is at __und_usr_fault_32+0x0/0x8

It turns out that the context save/restore fix unmasked a latent bug
in commit 5aaf2544 ("ARM: 6203/1: Make
VFPv3 usable on ARMv6").  When CONFIG_VFPv3 is set, but the kernel is
booted on a pre-VFPv3 core, the code attempts to save and restore the
d16-d31 VFP registers.  These are only present on non-D16 VFPv3+, so
this results in an undefined instruction exception.  The code didn't
crash before commit 846a1368 because the save and restore code was
only touching d0-d15, present on all VFP.

Fix by implementing a request from Russell King to add a new HWCAP
flag that affirmatively indicates the presence of the d16-d31
registers:

   http://marc.info/?l=linux-arm-kernel&m=135013547905283&w=2



and some feedback from Måns to clarify the name of the HWCAP flag.
Signed-off-by: default avatarPaul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Martin <dave.martin@linaro.org>
Cc: Måns Rullgård <mans.rullgard@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 6a4dae5e
......@@ -27,9 +27,9 @@
#if __LINUX_ARM_ARCH__ <= 6
ldr \tmp, =elf_hwcap @ may not have MVFR regs
ldr \tmp, [\tmp, #0]
tst \tmp, #HWCAP_VFPv3D16
ldceql p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register space
tst \tmp, #HWCAP_VFPD32
ldcnel p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31}
addeq \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
......@@ -51,9 +51,9 @@
#if __LINUX_ARM_ARCH__ <= 6
ldr \tmp, =elf_hwcap @ may not have MVFR regs
ldr \tmp, [\tmp, #0]
tst \tmp, #HWCAP_VFPv3D16
stceql p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register space
tst \tmp, #HWCAP_VFPD32
stcnel p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31}
addeq \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
......
......@@ -18,11 +18,12 @@
#define HWCAP_THUMBEE (1 << 11)
#define HWCAP_NEON (1 << 12)
#define HWCAP_VFPv3 (1 << 13)
#define HWCAP_VFPv3D16 (1 << 14)
#define HWCAP_VFPv3D16 (1 << 14) /* also set for VFPv4-D16 */
#define HWCAP_TLS (1 << 15)
#define HWCAP_VFPv4 (1 << 16)
#define HWCAP_IDIVA (1 << 17)
#define HWCAP_IDIVT (1 << 18)
#define HWCAP_VFPD32 (1 << 19) /* set if VFP has 32 regs (not 16) */
#define HWCAP_IDIV (HWCAP_IDIVA | HWCAP_IDIVT)
......
......@@ -701,11 +701,14 @@ static int __init vfp_init(void)
elf_hwcap |= HWCAP_VFPv3;
/*
* Check for VFPv3 D16. CPUs in this configuration
* only have 16 x 64bit registers.
* Check for VFPv3 D16 and VFPv4 D16. CPUs in
* this configuration only have 16 x 64bit
* registers.
*/
if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1)
elf_hwcap |= HWCAP_VFPv3D16;
elf_hwcap |= HWCAP_VFPv3D16; /* also v4-D16 */
else
elf_hwcap |= HWCAP_VFPD32;
}
#endif
/*
......
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment