diff mbox series

[10/20] mips/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()

Message ID 20190301140348.25175-11-will.deacon@arm.com
State Superseded
Headers show
Series Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb()) | expand

Commit Message

Will Deacon March 1, 2019, 2:03 p.m. UTC
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 mips. 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.

Signed-off-by: Will Deacon <will.deacon@arm.com>

---
 arch/mips/include/asm/Kbuild     |  1 -
 arch/mips/include/asm/io.h       |  3 ---
 arch/mips/include/asm/mmiowb.h   | 11 +++++++++++
 arch/mips/include/asm/spinlock.h | 15 +++++++++++++++
 4 files changed, 26 insertions(+), 4 deletions(-)
 create mode 100644 arch/mips/include/asm/mmiowb.h

-- 
2.11.0

Comments

Paul Burton March 1, 2019, 10:16 p.m. UTC | #1
Hi Will,

On Fri, Mar 01, 2019 at 02:03:38PM +0000, Will Deacon wrote:
> 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 mips. 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.

> 

> Signed-off-by: Will Deacon <will.deacon@arm.com>


Cleaning up our I/O functions has been on my to-do list for a while, so
I'll aim to get to that soon & get the calls to mmiowb_set_pending() in
place as part of it so that we can look at that optimization & drop the
custom queued_spin_unlock().

Meanwhile this looks sane & I don't want to hold it up so:

    Acked-by: Paul Burton <paul.burton@mips.com>


Thanks,
    Paul
diff mbox series

Patch

diff --git a/arch/mips/include/asm/Kbuild b/arch/mips/include/asm/Kbuild
index 5653b1e47dd0..f15d5db5dd67 100644
--- a/arch/mips/include/asm/Kbuild
+++ b/arch/mips/include/asm/Kbuild
@@ -13,7 +13,6 @@  generic-y += irq_work.h
 generic-y += local64.h
 generic-y += mcs_spinlock.h
 generic-y += mm-arch-hooks.h
-generic-y += mmiowb.h
 generic-y += msi.h
 generic-y += parport.h
 generic-y += percpu.h
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
index 845fbbc7a2e3..29997e42480e 100644
--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -102,9 +102,6 @@  static inline void set_io_port_base(unsigned long base)
 #define iobarrier_w() wmb()
 #define iobarrier_sync() iob()
 
-/* Some callers use this older API instead.  */
-#define mmiowb() iobarrier_w()
-
 /*
  *     virt_to_phys    -       map virtual addresses to physical
  *     @address: address to remap
diff --git a/arch/mips/include/asm/mmiowb.h b/arch/mips/include/asm/mmiowb.h
new file mode 100644
index 000000000000..a40824e3ef8e
--- /dev/null
+++ b/arch/mips/include/asm/mmiowb.h
@@ -0,0 +1,11 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_MMIOWB_H
+#define _ASM_MMIOWB_H
+
+#include <asm/io.h>
+
+#define mmiowb()	iobarrier_w()
+
+#include <asm-generic/mmiowb.h>
+
+#endif	/* _ASM_MMIOWB_H */
diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
index ee81297d9117..8a88eb265516 100644
--- a/arch/mips/include/asm/spinlock.h
+++ b/arch/mips/include/asm/spinlock.h
@@ -11,6 +11,21 @@ 
 
 #include <asm/processor.h>
 #include <asm/qrwlock.h>
+
+#include <asm-generic/qspinlock_types.h>
+
+#define	queued_spin_unlock queued_spin_unlock
+/**
+ * queued_spin_unlock - release a queued spinlock
+ * @lock : Pointer to queued spinlock structure
+ */
+static inline void queued_spin_unlock(struct qspinlock *lock)
+{
+	/* This could be optimised with ARCH_HAS_MMIOWB */
+	mmiowb();
+	smp_store_release(&lock->locked, 0);
+}
+
 #include <asm/qspinlock.h>
 
 #endif /* _ASM_SPINLOCK_H */