linux.git/arch/powerpc/include/asm/atomic.h, branch v6.5

locking/atomic: make atomic*_{cmp,}xchg optional

2023-06-05T07:57:14+00:00

Most architectures define the atomic/atomic64 xchg and cmpxchg
operations in terms of arch_xchg and arch_cmpxchg respectfully.

Add fallbacks for these cases and remove the trivial cases from arch
code. On some architectures the existing definitions are kept as these
are used to build other arch_atomic*() operations.

Signed-off-by: Mark Rutland 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Kees Cook 
Link: https://lore.kernel.org/r/20230605070124.3741859-5-mark.rutland@arm.com

powerpc/64: Add support to build with prefixed instructions

2023-04-20T02:54:22+00:00

Add an option to build kernel and module with prefixed instructions if
the CPU and toolchain support it.

This is not related to kernel support for userspace execution of
prefixed instructions.

Building with prefixed instructions breaks some extended inline asm
memory addressing, for example it will provide immediates that exceed
the range of simple load/store displacement. Whether this is a
toolchain or a kernel asm problem remains to be seen. For now, these
are replaced with simpler and less efficient direct register addressing
when compiling with prefixed.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230408021752.862660-4-npiggin@gmail.com

powerpc/atomics: Remove unused function

2023-04-04T12:11:03+00:00

Remove arch_atomic_try_cmpxchg_lock function as it is no longer used
since commit 9f61521c7a28 ("powerpc/qspinlock: powerpc qspinlock
implementation")

Signed-off-by: Nysal Jan K.A 
Reviewed-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230224103940.1328725-1-nysal@linux.ibm.com

powerpc: Make eh value more explicit when using lwarx

2022-08-10T05:32:20+00:00

Just like the first patch of this series, define a local 'eh' in order
to make the code clearer.

And IS_ENABLED() returns either 1 or 0 so no need to do
IS_ENABLED(CONFIG_PPC64) ? 1 : 0.

Signed-off-by: Christophe Leroy 
[mpe: Use symbolic names, use 'n' constraint per Segher]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/629befaa2d05e2922346e58a383886510d6af55a.1659430931.git.christophe.leroy@csgroup.eu

powerpc/atomics: Remove atomic_inc()/atomic_dec() and friends

2021-11-30T00:45:57+00:00

Now that atomic_add() and atomic_sub() handle immediate operands,
atomic_inc() and atomic_dec() have no added value compared to the
generic fallback which calls atomic_add(1) and atomic_sub(1).

Also remove atomic_inc_not_zero() which fallsback to
atomic_add_unless() which itself fallsback to
atomic_fetch_add_unless() which now handles immediate operands.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/0bc64a2f18726055093dbb2e479cefc60a409cfd.1632236981.git.christophe.leroy@csgroup.eu

powerpc/atomics: Use immediate operand when possible

2021-11-30T00:45:57+00:00

Today we get the following code generation for atomic operations:

	c001bb2c:	39 20 00 01 	li      r9,1
	c001bb30:	7d 40 18 28 	lwarx   r10,0,r3
	c001bb34:	7d 09 50 50 	subf    r8,r9,r10
	c001bb38:	7d 00 19 2d 	stwcx.  r8,0,r3

	c001c7a8:	39 40 00 01 	li      r10,1
	c001c7ac:	7d 00 18 28 	lwarx   r8,0,r3
	c001c7b0:	7c ea 42 14 	add     r7,r10,r8
	c001c7b4:	7c e0 19 2d 	stwcx.  r7,0,r3

By allowing GCC to choose between immediate or regular operation,
we get:

	c001bb2c:	7d 20 18 28 	lwarx   r9,0,r3
	c001bb30:	39 49 ff ff 	addi    r10,r9,-1
	c001bb34:	7d 40 19 2d 	stwcx.  r10,0,r3
	--
	c001c7a4:	7d 40 18 28 	lwarx   r10,0,r3
	c001c7a8:	39 0a 00 01 	addi    r8,r10,1
	c001c7ac:	7d 00 19 2d 	stwcx.  r8,0,r3

For "and", the dot form has to be used because "andi" doesn't exist.

For logical operations we use unsigned 16 bits immediate.
For arithmetic operations we use signed 16 bits immediate.

On pmac32_defconfig, it reduces the text by approx another 8 kbytes.

Signed-off-by: Christophe Leroy 
Acked-by: Segher Boessenkool 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/2ec558d44db8045752fe9dbd29c9ba84bab6030b.1632236981.git.christophe.leroy@csgroup.eu

powerpc/asm: Remove UPD_CONSTR after GCC 4.9 removal

2021-10-08T13:15:59+00:00

UPD_CONSTR was previously a preprocessor define for an old GCC 4.9
inline asm bug with m<> constraints.

Fixes: 6563139d90ad ("powerpc: remove GCC version check for UPD_CONSTR")
Suggested-by: Nathan Chancellor 
Suggested-by: Christophe Leroy 
Suggested-by: Michael Ellerman 
Signed-off-by: Nick Desaulniers 
Reviewed-by: Nathan Chancellor 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210914161712.2463458-1-ndesaulniers@google.com

powerpc: Use lwarx/ldarx directly instead of PPC_LWARX/LDARX macros

2021-08-25T03:35:49+00:00

Force the eh flag at 0 on PPC32.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/1fc81f07cabebb875b963e295408cc3dd38c8d85.1614674882.git.christophe.leroy@csgroup.eu

locking/atomic: powerpc: move to ARCH_ATOMIC

2021-05-26T11:20:52+00:00

We'd like all architectures to convert to ARCH_ATOMIC, as once all
architectures are converted it will be possible to make significant
cleanups to the atomics headers, and this will make it much easier to
generically enable atomic functionality (e.g. debug logic in the
instrumented wrappers).

As a step towards that, this patch migrates powerpc to ARCH_ATOMIC. The
arch code provides arch_{atomic,atomic64,xchg,cmpxchg}*(), and common
code wraps these with optional instrumentation to provide the regular
functions.

While atomic_try_cmpxchg_lock() is not part of the common atomic API, it
is given an `arch_` prefix for consistency.

Signed-off-by: Mark Rutland 
Cc: Benjamin Herrenschmidt 
Cc: Boqun Feng 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Cc: Peter Zijlstra 
Cc: Will Deacon 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210525140232.53872-28-mark.rutland@arm.com

powerpc: Fix update form addressing in inline assembly

2020-12-04T11:13:19+00:00

In several places, inline assembly uses the "%Un" modifier
to enable the use of instruction with update form addressing,
but the associated "<>" constraint is missing.

As mentioned in previous patch, this fails with gcc 4.9, so
"<>" can't be used directly.

Use UPD_CONSTR macro everywhere %Un modifier is used.

Signed-off-by: Christophe Leroy 
Reviewed-by: Segher Boessenkool 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/62eab5ca595485c192de1765bdac099f633a21d0.1603358942.git.christophe.leroy@csgroup.eu