diff options
author | Ard Biesheuvel <ardb@kernel.org> | 2024-02-14 08:03:24 +0100 |
---|---|---|
committer | Russell King (Oracle) <rmk+kernel@armlinux.org.uk> | 2024-02-26 10:16:31 +0000 |
commit | b9920fdd5a751df129808e7fa512e9928223ee05 (patch) | |
tree | 0fabdf8cfec747ad6d92f424212e0b24339f1909 /arch/arm/kernel/iwmmxt.S | |
parent | c8c178e0aef1eb16c267500f702675a46ab2aace (diff) |
ARM: 9352/1: iwmmxt: Remove support for PJ4/PJ4B cores
PJ4 is a v7 core that incorporates a iWMMXt coprocessor. However, GCC
does not support this combination (its iWMMXt configuration always
implies v5te), and so there is no v6/v7 user space that actually makes
use of this, beyond generic support for things like setjmp() that
preserve/restore the iWMMXt register file using generic LDC/STC
instructions emitted in assembler. As [0] appears to imply, this logic
is triggered for the init process at boot, and so most user threads will
have a iWMMXt register context associated with it, even though it is
never used.
At this point, it is highly unlikely that such GCC support will ever
materialize (and Clang does not implement support for iWMMXt to begin
with).
This means that advertising iWMMXt support on these cores results in
context switch overhead without any associated benefit, and so it is
better to simply ignore the iWMMXt unit on these systems. So rip out the
support. Doing so also fixes the issue reported in [0] related to UNDEF
handling of co-processor #0/#1 instructions issued from user space
running in Thumb2 mode.
The PJ4 cores are used in four platforms: Armada 370/xp, Dove (Cubox,
d2plug), MMP2 (xo-1.75) and Berlin (Google TV). Out of these, only the
first is still widely used, but that one actually doesn't have iWMMXt
but instead has only VFPV3-D16, and so it is not impacted by this
change.
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218427 [0]
Fixes: 8bcba70cb5c22 ("ARM: entry: Disregard Thumb undef exception ...")
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Reviewed-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/kernel/iwmmxt.S')
-rw-r--r-- | arch/arm/kernel/iwmmxt.S | 51 |
1 files changed, 13 insertions, 38 deletions
diff --git a/arch/arm/kernel/iwmmxt.S b/arch/arm/kernel/iwmmxt.S index a0218c4867b9..4a335d3c5969 100644 --- a/arch/arm/kernel/iwmmxt.S +++ b/arch/arm/kernel/iwmmxt.S @@ -18,18 +18,6 @@ #include <asm/assembler.h> #include "iwmmxt.h" -#if defined(CONFIG_CPU_PJ4) || defined(CONFIG_CPU_PJ4B) -#define PJ4(code...) code -#define XSC(code...) -#elif defined(CONFIG_CPU_MOHAWK) || \ - defined(CONFIG_CPU_XSC3) || \ - defined(CONFIG_CPU_XSCALE) -#define PJ4(code...) -#define XSC(code...) code -#else -#error "Unsupported iWMMXt architecture" -#endif - #define MMX_WR0 (0x00) #define MMX_WR1 (0x08) #define MMX_WR2 (0x10) @@ -81,17 +69,13 @@ ENDPROC(iwmmxt_undef_handler) ENTRY(iwmmxt_task_enable) inc_preempt_count r10, r3 - XSC(mrc p15, 0, r2, c15, c1, 0) - PJ4(mrc p15, 0, r2, c1, c0, 2) + mrc p15, 0, r2, c15, c1, 0 @ CP0 and CP1 accessible? - XSC(tst r2, #0x3) - PJ4(tst r2, #0xf) + tst r2, #0x3 bne 4f @ if so no business here @ enable access to CP0 and CP1 - XSC(orr r2, r2, #0x3) - XSC(mcr p15, 0, r2, c15, c1, 0) - PJ4(orr r2, r2, #0xf) - PJ4(mcr p15, 0, r2, c1, c0, 2) + orr r2, r2, #0x3 + mcr p15, 0, r2, c15, c1, 0 ldr r3, =concan_owner ldr r2, [r0, #S_PC] @ current task pc value @@ -218,12 +202,9 @@ ENTRY(iwmmxt_task_disable) bne 1f @ no: quit @ enable access to CP0 and CP1 - XSC(mrc p15, 0, r4, c15, c1, 0) - XSC(orr r4, r4, #0x3) - XSC(mcr p15, 0, r4, c15, c1, 0) - PJ4(mrc p15, 0, r4, c1, c0, 2) - PJ4(orr r4, r4, #0xf) - PJ4(mcr p15, 0, r4, c1, c0, 2) + mrc p15, 0, r4, c15, c1, 0 + orr r4, r4, #0x3 + mcr p15, 0, r4, c15, c1, 0 mov r0, #0 @ nothing to load str r0, [r3] @ no more current owner @@ -232,10 +213,8 @@ ENTRY(iwmmxt_task_disable) bl concan_save @ disable access to CP0 and CP1 - XSC(bic r4, r4, #0x3) - XSC(mcr p15, 0, r4, c15, c1, 0) - PJ4(bic r4, r4, #0xf) - PJ4(mcr p15, 0, r4, c1, c0, 2) + bic r4, r4, #0x3 + mcr p15, 0, r4, c15, c1, 0 mrc p15, 0, r2, c2, c0, 0 mov r2, r2 @ cpwait @@ -330,11 +309,9 @@ ENDPROC(iwmmxt_task_restore) */ ENTRY(iwmmxt_task_switch) - XSC(mrc p15, 0, r1, c15, c1, 0) - PJ4(mrc p15, 0, r1, c1, c0, 2) + mrc p15, 0, r1, c15, c1, 0 @ CP0 and CP1 accessible? - XSC(tst r1, #0x3) - PJ4(tst r1, #0xf) + tst r1, #0x3 bne 1f @ yes: block them for next task ldr r2, =concan_owner @@ -344,10 +321,8 @@ ENTRY(iwmmxt_task_switch) retne lr @ no: leave Concan disabled 1: @ flip Concan access - XSC(eor r1, r1, #0x3) - XSC(mcr p15, 0, r1, c15, c1, 0) - PJ4(eor r1, r1, #0xf) - PJ4(mcr p15, 0, r1, c1, c0, 2) + eor r1, r1, #0x3 + mcr p15, 0, r1, c15, c1, 0 mrc p15, 0, r1, c2, c0, 0 sub pc, lr, r1, lsr #32 @ cpwait and return |