• Paul Walmsley's avatar
    ARM: 7566/1: vfp: fix save and restore when running on pre-VFPv3 and CONFIG_VFPv3 set · 39141ddf
    Paul Walmsley authored
    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>
    39141ddf
hwcap.h 884 Bytes