Fixed MTP to work with TWRP

arch/tile/lib/atomic_asm_32.S

@@ -0,0 +1,197 @@
+/*
+ * Copyright 2010 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ *
+ * Support routines for atomic operations.  Each function takes:
+ *
+ * r0: address to manipulate
+ * r1: pointer to atomic lock guarding this operation (for ATOMIC_LOCK_REG)
+ * r2: new value to write, or for cmpxchg/add_unless, value to compare against
+ * r3: (cmpxchg/xchg_add_unless) new value to write or add;
+ *     (atomic64 ops) high word of value to write
+ * r4/r5: (cmpxchg64/add_unless64) new value to write or add
+ *
+ * The 32-bit routines return a "struct __get_user" so that the futex code
+ * has an opportunity to return -EFAULT to the user if needed.
+ * The 64-bit routines just return a "long long" with the value,
+ * since they are only used from kernel space and don't expect to fault.
+ * Support for 16-bit ops is included in the framework but we don't provide
+ * any (x86_64 has an atomic_inc_short(), so we might want to some day).
+ *
+ * Note that the caller is advised to issue a suitable L1 or L2
+ * prefetch on the address being manipulated to avoid extra stalls.
+ * In addition, the hot path is on two icache lines, and we start with
+ * a jump to the second line to make sure they are both in cache so
+ * that we never stall waiting on icache fill while holding the lock.
+ * (This doesn't work out with most 64-bit ops, since they consume
+ * too many bundles, so may take an extra i-cache stall.)
+ *
+ * These routines set the INTERRUPT_CRITICAL_SECTION bit, just
+ * like sys_cmpxchg(), so that NMIs like PERF_COUNT will not interrupt
+ * the code, just page faults.
+ *
+ * If the load or store faults in a way that can be directly fixed in
+ * the do_page_fault_ics() handler (e.g. a vmalloc reference) we fix it
+ * directly, return to the instruction that faulted, and retry it.
+ *
+ * If the load or store faults in a way that potentially requires us
+ * to release the atomic lock, then retry (e.g. a migrating PTE), we
+ * reset the PC in do_page_fault_ics() to the "tns" instruction so
+ * that on return we will reacquire the lock and restart the op.  We
+ * are somewhat overloading the exception_table_entry notion by doing
+ * this, since those entries are not normally used for migrating PTEs.
+ *
+ * If the main page fault handler discovers a bad address, it will see
+ * the PC pointing to the "tns" instruction (due to the earlier
+ * exception_table_entry processing in do_page_fault_ics), and
+ * re-reset the PC to the fault handler, atomic_bad_address(), which
+ * effectively takes over from the atomic op and can either return a
+ * bad "struct __get_user" (for user addresses) or can just panic (for
+ * bad kernel addresses).
+ *
+ * Note that if the value we would store is the same as what we
+ * loaded, we bypass the store.  Other platforms with true atomics can
+ * make the guarantee that a non-atomic __clear_bit(), for example,
+ * can safely race with an atomic test_and_set_bit(); this example is
+ * from bit_spinlock.h in slub_lock() / slub_unlock().  We can't do
+ * that on Tile since the "atomic" op is really just a
+ * read/modify/write, and can race with the non-atomic
+ * read/modify/write.  However, if we can short-circuit the write when
+ * it is not needed, in the atomic case, we avoid the race.
+ */
+
+#include <linux/linkage.h>
+#include <asm/atomic_32.h>
+#include <asm/page.h>
+#include <asm/processor.h>
+
+	.section .text.atomic,"ax"
+ENTRY(__start_atomic_asm_code)
+
+	.macro  atomic_op, name, bitwidth, body
+	.align  64
+STD_ENTRY_SECTION(__atomic\name, .text.atomic)
+	{
+	 movei  r24, 1
+	 j      4f		/* branch to second cache line */
+	}
+1:	{
+	 .ifc \bitwidth,16
+	 lh     r22, r0
+	 .else
+	 lw     r22, r0
+	 addi   r28, r0, 4
+	 .endif
+	}
+	.ifc \bitwidth,64
+	lw      r23, r28
+	.endif
+	\body /* set r24, and r25 if 64-bit */
+	{
+	 seq    r26, r22, r24
+	 seq    r27, r23, r25
+	}
+	.ifc \bitwidth,64
+	bbnst   r27, 2f
+	.endif
+	bbs     r26, 3f		/* skip write-back if it's the same value */
+2:	{
+	 .ifc \bitwidth,16
+	 sh     r0, r24
+	 .else
+	 sw     r0, r24
+	 .endif
+	}
+	.ifc \bitwidth,64
+	sw      r28, r25
+	.endif
+	mf
+3:	{
+	 move   r0, r22
+	 .ifc \bitwidth,64
+	 move   r1, r23
+	 .else
+	 move   r1, zero
+	 .endif
+	 sw     ATOMIC_LOCK_REG_NAME, zero
+	}
+	mtspr   INTERRUPT_CRITICAL_SECTION, zero
+	jrp     lr
+4:	{
+	 move   ATOMIC_LOCK_REG_NAME, r1
+	 mtspr  INTERRUPT_CRITICAL_SECTION, r24
+	}
+#ifndef CONFIG_SMP
+	j       1b		/* no atomic locks */
+#else
+	{
+	 tns    r21, ATOMIC_LOCK_REG_NAME
+	 moveli r23, 2048       /* maximum backoff time in cycles */
+	}
+	{
+	 bzt    r21, 1b		/* branch if lock acquired */
+	 moveli r25, 32         /* starting backoff time in cycles */
+	}
+5:	mtspr   INTERRUPT_CRITICAL_SECTION, zero
+	mfspr   r26, CYCLE_LOW  /* get start point for this backoff */
+6:	mfspr   r22, CYCLE_LOW  /* test to see if we've backed off enough */
+	sub     r22, r22, r26
+	slt     r22, r22, r25
+	bbst    r22, 6b
+	{
+	 mtspr  INTERRUPT_CRITICAL_SECTION, r24
+	 shli   r25, r25, 1     /* double the backoff; retry the tns */
+	}
+	{
+	 tns    r21, ATOMIC_LOCK_REG_NAME
+	 slt    r26, r23, r25   /* is the proposed backoff too big? */
+	}
+	{
+	 bzt    r21, 1b		/* branch if lock acquired */
+	 mvnz   r25, r26, r23
+	}
+	j       5b
+#endif
+	STD_ENDPROC(__atomic\name)
+	.ifc \bitwidth,32
+	.pushsection __ex_table,"a"
+	.align  4
+	.word   1b, __atomic\name
+	.word   2b, __atomic\name
+	.word   __atomic\name, __atomic_bad_address
+	.popsection
+	.endif
+	.endm
+
+atomic_op _cmpxchg, 32, "seq r26, r22, r2; { bbns r26, 3f; move r24, r3 }"
+atomic_op _xchg, 32, "move r24, r2"
+atomic_op _xchg_add, 32, "add r24, r22, r2"
+atomic_op _xchg_add_unless, 32, \
+	"sne r26, r22, r2; { bbns r26, 3f; add r24, r22, r3 }"
+atomic_op _or, 32, "or r24, r22, r2"
+atomic_op _andn, 32, "nor r2, r2, zero; and r24, r22, r2"
+atomic_op _xor, 32, "xor r24, r22, r2"
+
+atomic_op 64_cmpxchg, 64, "{ seq r26, r22, r2; seq r27, r23, r3 }; \
+	{ bbns r26, 3f; move r24, r4 }; { bbns r27, 3f; move r25, r5 }"
+atomic_op 64_xchg, 64, "{ move r24, r2; move r25, r3 }"
+atomic_op 64_xchg_add, 64, "{ add r24, r22, r2; add r25, r23, r3 }; \
+	slt_u r26, r24, r22; add r25, r25, r26"
+atomic_op 64_xchg_add_unless, 64, \
+	"{ sne r26, r22, r2; sne r27, r23, r3 }; \
+	{ bbns r26, 3f; add r24, r22, r4 }; \
+	{ bbns r27, 3f; add r25, r23, r5 }; \
+	slt_u r26, r24, r22; add r25, r25, r26"
+
+	jrp     lr              /* happy backtracer */
+
+ENTRY(__end_atomic_asm_code)