In a bid to kill off explicit mmiowb() usage in driver code, hook up
the asm-generic mmiowb() tracking code but override all of the functions
so that the existing (flawed) implementation is preserved on Power.
Future work should either use the asm-generic implementation entirely,
or implement a similar counting mechanism to avoid erroneously skipping
barrier invocations when they are needed.
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/Kbuild | 1 -
arch/powerpc/include/asm/io.h | 33 +++--------------------------
arch/powerpc/include/asm/mmiowb.h | 41 +++++++++++++++++++++++++++++++++++++
arch/powerpc/include/asm/spinlock.h | 17 ---------------
5 files changed, 45 insertions(+), 48 deletions(-)
create mode 100644 arch/powerpc/include/asm/mmiowb.h
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2890d36eb531..242ee248b922 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -134,6 +134,7 @@ config PPC
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
+ select ARCH_HAS_MMIOWB if PPC64 && SMP
select ARCH_HAS_PHYS_TO_DMA
select ARCH_HAS_PMEM_API if PPC64
select ARCH_HAS_PTE_SPECIAL
diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
index 57bd1f6660f4..77ff7fb24823 100644
--- a/arch/powerpc/include/asm/Kbuild
+++ b/arch/powerpc/include/asm/Kbuild
@@ -8,7 +8,6 @@ generic-y += irq_regs.h
generic-y += irq_work.h
generic-y += local64.h
generic-y += mcs_spinlock.h
-generic-y += mmiowb.h
generic-y += preempt.h
generic-y += rwsem.h
generic-y += vtime.h
diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
index 7f19fbd3ba55..828100476ba6 100644
--- a/arch/powerpc/include/asm/io.h
+++ b/arch/powerpc/include/asm/io.h
@@ -34,14 +34,11 @@ extern struct pci_dev *isa_bridge_pcidev;
#include <asm/byteorder.h>
#include <asm/synch.h>
#include <asm/delay.h>
+#include <asm/mmiowb.h>
#include <asm/mmu.h>
#include <asm/ppc_asm.h>
#include <asm/pgtable.h>
-#ifdef CONFIG_PPC64
-#include <asm/paca.h>
-#endif
-
#define SIO_CONFIG_RA 0x398
#define SIO_CONFIG_RD 0x399
@@ -107,12 +104,6 @@ extern bool isa_io_special;
*
*/
-#ifdef CONFIG_PPC64
-#define IO_SET_SYNC_FLAG() do { local_paca->io_sync = 1; } while(0)
-#else
-#define IO_SET_SYNC_FLAG()
-#endif
-
#define DEF_MMIO_IN_X(name, size, insn) \
static inline u##size name(const volatile u##size __iomem *addr) \
{ \
@@ -127,7 +118,7 @@ static inline void name(volatile u##size __iomem *addr, u##size val) \
{ \
__asm__ __volatile__("sync;"#insn" %1,%y0" \
: "=Z" (*addr) : "r" (val) : "memory"); \
- IO_SET_SYNC_FLAG(); \
+ mmiowb_set_pending(); \
}
#define DEF_MMIO_IN_D(name, size, insn) \
@@ -144,7 +135,7 @@ static inline void name(volatile u##size __iomem *addr, u##size val) \
{ \
__asm__ __volatile__("sync;"#insn"%U0%X0 %1,%0" \
: "=m" (*addr) : "r" (val) : "memory"); \
- IO_SET_SYNC_FLAG(); \
+ mmiowb_set_pending(); \
}
DEF_MMIO_IN_D(in_8, 8, lbz);
@@ -652,24 +643,6 @@ static inline void name at \
#include <asm-generic/iomap.h>
-#ifdef CONFIG_PPC32
-#define mmiowb()
-#else
-/*
- * Enforce synchronisation of stores vs. spin_unlock
- * (this does it explicitly, though our implementation of spin_unlock
- * does it implicitely too)
- */
-static inline void mmiowb(void)
-{
- unsigned long tmp;
-
- __asm__ __volatile__("sync; li %0,0; stb %0,%1(13)"
- : "=&r" (tmp) : "i" (offsetof(struct paca_struct, io_sync))
- : "memory");
-}
-#endif /* !CONFIG_PPC32 */
-
static inline void iosync(void)
{
__asm__ __volatile__ ("sync" : : : "memory");
diff --git a/arch/powerpc/include/asm/mmiowb.h b/arch/powerpc/include/asm/mmiowb.h
new file mode 100644
index 000000000000..7647ffcced1c
--- /dev/null
+++ b/arch/powerpc/include/asm/mmiowb.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_POWERPC_MMIOWB_H
+#define _ASM_POWERPC_MMIOWB_H
+
+#ifdef CONFIG_ARCH_HAS_MMIOWB
+
+#include <linux/compiler.h>
+#include <asm/barrier.h>
+#include <asm/paca.h>
+
+#define mmiowb() mb()
+
+/*
+ * Note: this is broken, as it doesn't correctly handle sequences such as:
+ *
+ * spin_lock(&foo); // io_sync = 0
+ * outb(42, port); // io_sync = 1
+ * spin_lock(&bar); // io_sync = 0
+ * ...
+ * spin_unlock(&bar);
+ * spin_unlock(&foo);
+ *
+ * The implementation in asm-generic/mmiowb.h deals with this by counting
+ * the critical sections.
+ */
+#define mmiowb_set_pending() do { local_paca->io_sync = 1; } while (0)
+#define mmiowb_spin_lock() do { get_paca()->io_sync = 0; } while (0)
+
+#define mmiowb_spin_unlock() do { \
+ if (unlikely(get_paca()->io_sync)) { \
+ mmiowb(); \
+ get_paca()->io_sync = 0; \
+ } \
+} while (0)
+#else
+#define mmiowb() do { } while (0)
+#endif /* CONFIG_ARCH_HAS_MMIOWB */
+
+#include <asm-generic/mmiowb.h>
+
+#endif /* _ASM_POWERPC_MMIOWB_H */
diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
index 685c72310f5d..15b39c407c4e 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -39,19 +39,6 @@
#define LOCK_TOKEN 1
#endif
-#if defined(CONFIG_PPC64) && defined(CONFIG_SMP)
-#define CLEAR_IO_SYNC (get_paca()->io_sync = 0)
-#define SYNC_IO do { \
- if (unlikely(get_paca()->io_sync)) { \
- mb(); \
- get_paca()->io_sync = 0; \
- } \
- } while (0)
-#else
-#define CLEAR_IO_SYNC
-#define SYNC_IO
-#endif
-
#ifdef CONFIG_PPC_PSERIES
#define vcpu_is_preempted vcpu_is_preempted
static inline bool vcpu_is_preempted(int cpu)
@@ -99,7 +86,6 @@ static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
- CLEAR_IO_SYNC;
return __arch_spin_trylock(lock) == 0;
}
@@ -130,7 +116,6 @@ extern void __rw_yield(arch_rwlock_t *lock);
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
- CLEAR_IO_SYNC;
while (1) {
if (likely(__arch_spin_trylock(lock) == 0))
break;
@@ -148,7 +133,6 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
{
unsigned long flags_dis;
- CLEAR_IO_SYNC;
while (1) {
if (likely(__arch_spin_trylock(lock) == 0))
break;
@@ -167,7 +151,6 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
- SYNC_IO;
__asm__ __volatile__("# arch_spin_unlock\n\t"
PPC_RELEASE_BARRIER: : :"memory");
lock->slock = 0;
--
2.11.0
