Commit 49ca6462 authored by Will Deacon's avatar Will Deacon
Browse files

ia64/mmiowb: Add unconditional mmiowb() to arch_spin_unlock() 



The mmiowb() macro is horribly difficult to use and drivers will continue
to work most of the time if they omit a call when it is required.

Rather than rely on driver authors getting this right, push mmiowb() into
arch_spin_unlock() for ia64. If this is deemed to be a performance issue,
a subsequent optimisation could make use of ARCH_HAS_MMIOWB to elide
the barrier in cases where no I/O writes were performed inside the
critical section.

Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 346e91ee

arch/ia64/include/asm/Kbuild

+0 −1
Original line number Diff line number Diff line
@@ -5,7 +5,6 @@ generic-y += irq_work.h 
generic-y += kvm_para.h

generic-y += mcs_spinlock.h

generic-y += mm-arch-hooks.h

generic-y += mmiowb.h

generic-y += preempt.h

generic-y += trace_clock.h

generic-y += vtime.h

arch/ia64/include/asm/io.h

+0 −17
Original line number Diff line number Diff line
@@ -113,20 +113,6 @@ extern int valid_mmap_phys_addr_range (unsigned long pfn, size_t count); 
 */

#define __ia64_mf_a()	ia64_mfa()



/**

 * ___ia64_mmiowb - I/O write barrier

 *

 * Ensure ordering of I/O space writes.  This will make sure that writes

 * following the barrier will arrive after all previous writes.  For most

 * ia64 platforms, this is a simple 'mf.a' instruction.

 *

 * See Documentation/driver-api/device-io.rst for more information.

 */

static inline void ___ia64_mmiowb(void)

{

	ia64_mfa();

}



static inline void*

__ia64_mk_io_addr (unsigned long port)

{
@@ -161,7 +147,6 @@ __ia64_mk_io_addr (unsigned long port) 
#define __ia64_writew	___ia64_writew

#define __ia64_writel	___ia64_writel

#define __ia64_writeq	___ia64_writeq

#define __ia64_mmiowb	___ia64_mmiowb



/*

 * For the in/out routines, we need to do "mf.a" _after_ doing the I/O access to ensure
@@ -296,7 +281,6 @@ __outsl (unsigned long port, const void *src, unsigned long count) 
#define __outb		platform_outb

#define __outw		platform_outw

#define __outl		platform_outl

#define __mmiowb	platform_mmiowb



#define inb(p)		__inb(p)

#define inw(p)		__inw(p)
@@ -310,7 +294,6 @@ __outsl (unsigned long port, const void *src, unsigned long count) 
#define outsb(p,s,c)	__outsb(p,s,c)

#define outsw(p,s,c)	__outsw(p,s,c)

#define outsl(p,s,c)	__outsl(p,s,c)

#define mmiowb()	__mmiowb()



/*

 * The address passed to these functions are ioremap()ped already.

arch/ia64/include/asm/mmiowb.h

0 → 100644
+25 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */



#ifndef _ASM_IA64_MMIOWB_H

#define _ASM_IA64_MMIOWB_H



#include <asm/machvec.h>



/**

 * ___ia64_mmiowb - I/O write barrier

 *

 * Ensure ordering of I/O space writes.  This will make sure that writes

 * following the barrier will arrive after all previous writes.  For most

 * ia64 platforms, this is a simple 'mf.a' instruction.

 */

static inline void ___ia64_mmiowb(void)

{

	ia64_mfa();

}



#define __ia64_mmiowb	___ia64_mmiowb

#define mmiowb()	platform_mmiowb()



#include <asm-generic/mmiowb.h>



#endif	/* _ASM_IA64_MMIOWB_H */

arch/ia64/include/asm/spinlock.h

+2 −0
Original line number Diff line number Diff line
@@ -73,6 +73,8 @@ static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock) 
{

	unsigned short	*p = (unsigned short *)&lock->lock + 1, tmp;



	/* This could be optimised with ARCH_HAS_MMIOWB */

	mmiowb();

	asm volatile ("ld2.bias %0=[%1]" : "=r"(tmp) : "r"(p));

	WRITE_ONCE(*p, (tmp + 2) & ~1);

}