[ARM] 4584/2: ARMv7: Add Advanced SIMD (NEON) extension support

This patch enables the use of the Advanced SIMD (NEON) extension on
ARMv7. The NEON technology is a 64/128-bit hybrid SIMD architecture
for accelerating the performance of multimedia and signal processing
applications. The extension shares the registers with the VFP unit and
enabling/disabling and saving/restoring follow the same rules. In
addition, there are instructions that do not have the appropriate CP
number encoded, the checks being made in the call_fpe function.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 45 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index f4eeb03bc6a9..709f9d383c87 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -966,6 +966,13 @@ config VFPv3
         depends on VFP
         default y if CPU_V7
 
+config NEON
+        bool "Advanced SIMD (NEON) Extension support"
+        depends on VFPv3 && CPU_V7
+        help
+          Say Y to include support code for NEON, the ARMv7 Advanced SIMD
+          Extension.
+
 endmenu
 
 menu "Userspace binary formats"
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 29dec080a604..8de21f51e48c 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -480,6 +480,13 @@ __und_usr:
  * co-processor instructions.  However, we have to watch out
  * for the ARM6/ARM7 SWI bug.
  *
+ * NEON is a special case that has to be handled here. Not all
+ * NEON instructions are co-processor instructions, so we have
+ * to make a special case of checking for them. Plus, there's
+ * five groups of them, so we have a table of mask/opcode pairs
+ * to check against, and if any match then we branch off into the
+ * NEON handler code.
+ *
  * Emulators may wish to make use of the following registers:
  *  r0  = instruction opcode.
  *  r2  = PC+4
@@ -488,6 +495,23 @@ __und_usr:
  *  lr  = unrecognised instruction return address
  */
 call_fpe:
+#ifdef CONFIG_NEON
+        adr     r6, .LCneon_opcodes
+2:
+        ldr     r7, [r6], #4                    @ mask value
+        cmp     r7, #0                          @ end mask?
+        beq     1f
+        and     r8, r0, r7
+        ldr     r7, [r6], #4                    @ opcode bits matching in mask
+        cmp     r8, r7                          @ NEON instruction?
+        bne     2b
+        get_thread_info r10
+        mov     r7, #1
+        strb    r7, [r10, #TI_USED_CP + 10]     @ mark CP#10 as used
+        strb    r7, [r10, #TI_USED_CP + 11]     @ mark CP#11 as used
+        b       do_vfp                          @ let VFP handler handle this
+1:
+#endif
         tst     r0, #0x08000000                 @ only CDP/CPRT/LDC/STC have bit 27
 #if defined(CONFIG_CPU_ARM610) || defined(CONFIG_CPU_ARM710)
         and     r8, r0, #0x0f000000             @ mask out op-code bits
@@ -537,6 +561,20 @@ call_fpe:
         mov     pc, lr                          @ CP#14 (Debug)
         mov     pc, lr                          @ CP#15 (Control)
 
+#ifdef CONFIG_NEON
+        .align  6
+
+.LCneon_opcodes:
+        .word   0xfe000000                      @ mask
+        .word   0xf2000000                      @ opcode
+
+        .word   0xff100000                      @ mask
+        .word   0xf4000000                      @ opcode
+
+        .word   0x00000000                      @ mask
+        .word   0x00000000                      @ opcode
+#endif
+
 do_fpe:
         enable_irq
         ldr     r4, .LCfp