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    Subject[PATCH 13/20] riscv/mmiowb: Hook up mmwiob() implementation to asm-generic code
    Date
    In a bid to kill off explicit mmiowb() usage in driver code, hook up
    the asm-generic mmiowb() tracking code for riscv, so that an mmiowb()
    is automatically issued from spin_unlock() if an I/O write was performed
    in the critical section.

    Signed-off-by: Will Deacon <will.deacon@arm.com>
    ---
    arch/riscv/Kconfig | 1 +
    arch/riscv/include/asm/Kbuild | 1 -
    arch/riscv/include/asm/io.h | 15 ++-------------
    arch/riscv/include/asm/mmiowb.h | 14 ++++++++++++++
    4 files changed, 17 insertions(+), 14 deletions(-)
    create mode 100644 arch/riscv/include/asm/mmiowb.h

    diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
    index 515fc3cc9687..08f4415203c5 100644
    --- a/arch/riscv/Kconfig
    +++ b/arch/riscv/Kconfig
    @@ -49,6 +49,7 @@ config RISCV
    select RISCV_TIMER
    select GENERIC_IRQ_MULTI_HANDLER
    select ARCH_HAS_PTE_SPECIAL
    + select ARCH_HAS_MMIOWB

    config MMU
    def_bool y
    diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
    index 221cd2ec78a4..cccd12cf27d4 100644
    --- a/arch/riscv/include/asm/Kbuild
    +++ b/arch/riscv/include/asm/Kbuild
    @@ -21,7 +21,6 @@ generic-y += kvm_para.h
    generic-y += local.h
    generic-y += local64.h
    generic-y += mm-arch-hooks.h
    -generic-y += mmiowb.h
    generic-y += mutex.h
    generic-y += percpu.h
    generic-y += preempt.h
    diff --git a/arch/riscv/include/asm/io.h b/arch/riscv/include/asm/io.h
    index 1d9c1376dc64..744fd92e77bc 100644
    --- a/arch/riscv/include/asm/io.h
    +++ b/arch/riscv/include/asm/io.h
    @@ -20,6 +20,7 @@
    #define _ASM_RISCV_IO_H

    #include <linux/types.h>
    +#include <asm/mmiowb.h>

    extern void __iomem *ioremap(phys_addr_t offset, unsigned long size);

    @@ -100,18 +101,6 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
    #endif

    /*
    - * FIXME: I'm flip-flopping on whether or not we should keep this or enforce
    - * the ordering with I/O on spinlocks like PowerPC does. The worry is that
    - * drivers won't get this correct, but I also don't want to introduce a fence
    - * into the lock code that otherwise only uses AMOs (and is essentially defined
    - * by the ISA to be correct). For now I'm leaving this here: "o,w" is
    - * sufficient to ensure that all writes to the device have completed before the
    - * write to the spinlock is allowed to commit. I surmised this from reading
    - * "ACQUIRES VS I/O ACCESSES" in memory-barriers.txt.
    - */
    -#define mmiowb() __asm__ __volatile__ ("fence o,w" : : : "memory");
    -
    -/*
    * Unordered I/O memory access primitives. These are even more relaxed than
    * the relaxed versions, as they don't even order accesses between successive
    * operations to the I/O regions.
    @@ -165,7 +154,7 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
    #define __io_br() do {} while (0)
    #define __io_ar(v) __asm__ __volatile__ ("fence i,r" : : : "memory");
    #define __io_bw() __asm__ __volatile__ ("fence w,o" : : : "memory");
    -#define __io_aw() do {} while (0)
    +#define __io_aw() mmiowb_set_pending()

    #define readb(c) ({ u8 __v; __io_br(); __v = readb_cpu(c); __io_ar(__v); __v; })
    #define readw(c) ({ u16 __v; __io_br(); __v = readw_cpu(c); __io_ar(__v); __v; })
    diff --git a/arch/riscv/include/asm/mmiowb.h b/arch/riscv/include/asm/mmiowb.h
    new file mode 100644
    index 000000000000..5d7e3a2b4e3b
    --- /dev/null
    +++ b/arch/riscv/include/asm/mmiowb.h
    @@ -0,0 +1,14 @@
    +/* SPDX-License-Identifier: GPL-2.0 */
    +
    +#ifndef _ASM_RISCV_MMIOWB_H
    +#define _ASM_RISCV_MMIOWB_H
    +
    +/*
    + * "o,w" is sufficient to ensure that all writes to the device have completed
    + * before the write to the spinlock is allowed to commit.
    + */
    +#define mmiowb() __asm__ __volatile__ ("fence o,w" : : : "memory");
    +
    +#include <asm-generic/mmiowb.h>
    +
    +#endif /* ASM_RISCV_MMIOWB_H */
    --
    2.11.0
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