From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Mon, 5 Oct 2015 17:00:18 +0100 Subject: [PATCH v2] arm: Adding support for atomic half word exchange In-Reply-To: <1912649938.590071444050653292.JavaMail.weblogic@epmlwas01c> References: <1912649938.590071444050653292.JavaMail.weblogic@epmlwas01c> Message-ID: <20151005160017.GA3211@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Oct 05, 2015 at 01:10:53PM +0000, Sarbojit Ganguly wrote: > My sincere apologies for the format issue. This was due to the e-mail editor > which reformats the text. > I am reposting the patch, please let me know if it is ok this time. > > > v1-->v2 : Extended the guard code to cover the byte exchange case as > well following opinion of Will Deacon. > Checkpatch has been run and issues were taken care of. > > Since support for half-word atomic exchange was not there and Qspinlock > on ARM requires it, modified __xchg() to add support for that as well. > ARMv6 and lower does not support ldrex{b,h} so, added a guard code > to prevent build breaks. > > Signed-off-by: Sarbojit Ganguly > --- > arch/arm/include/asm/cmpxchg.h | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h > index 916a274..a53cbeb 100644 > --- a/arch/arm/include/asm/cmpxchg.h > +++ b/arch/arm/include/asm/cmpxchg.h > @@ -39,6 +39,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size > > switch (size) { > #if __LINUX_ARM_ARCH__ >= 6 > +#if !defined(CONFIG_CPU_V6) #ifndef ? (to match the __cmpxchg code). > case 1: > asm volatile("@ __xchg1\n" > "1: ldrexb %0, [%3]\n" > @@ -49,6 +50,22 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size > : "r" (x), "r" (ptr) > : "memory", "cc"); > break; > + > + /* > + * Half-word atomic exchange, required > + * for Qspinlock support on ARM. > + */ I think I said it before, but I don't think this comment is of any real value. Other than those, this looks ok to me. Will