lkml.org 
[lkml]   [2013]   [Aug]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v4 1/4] lib: Introduce atomic MMIO modify
    Date
    Some platforms have MMIO regions that are shared across orthogonal
    subsystems. This commit implements a possible solution for the
    thread-safe access of such regions through a spinlock-protected API.

    Concurrent access is protected with a single spinlock for the
    entire MMIO address space. While this protects shared-registers,
    it also serializes access to unrelated/unshared registers.

    Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
    ---
    include/linux/io.h | 5 +++++
    lib/Makefile | 2 +-
    lib/atomicio.c | 27 +++++++++++++++++++++++++++
    3 files changed, 33 insertions(+), 1 deletion(-)
    create mode 100644 lib/atomicio.c

    diff --git a/include/linux/io.h b/include/linux/io.h
    index f4f42fa..c331dcb 100644
    --- a/include/linux/io.h
    +++ b/include/linux/io.h
    @@ -101,4 +101,9 @@ static inline void arch_phys_wc_del(int handle)
    #define arch_phys_wc_add arch_phys_wc_add
    #endif

    +#ifndef __HAVE_ARCH_ATOMIC_IO_MODIFY
    +/* Atomic MMIO-wide IO modify */
    +extern void atomic_io_modify(void __iomem *reg, u32 mask, u32 set);
    +#endif
    +
    #endif /* _LINUX_IO_H */
    diff --git a/lib/Makefile b/lib/Makefile
    index 7baccfd..695d6e2 100644
    --- a/lib/Makefile
    +++ b/lib/Makefile
    @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
    sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \
    proportions.o flex_proportions.o prio_heap.o ratelimit.o show_mem.o \
    is_single_threaded.o plist.o decompress.o kobject_uevent.o \
    - earlycpio.o percpu-refcount.o
    + earlycpio.o percpu-refcount.o atomicio.o

    obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
    lib-$(CONFIG_MMU) += ioremap.o
    diff --git a/lib/atomicio.c b/lib/atomicio.c
    new file mode 100644
    index 0000000..1750f9d
    --- /dev/null
    +++ b/lib/atomicio.c
    @@ -0,0 +1,27 @@
    +#include <linux/io.h>
    +#include <linux/spinlock.h>
    +
    +#ifndef __HAVE_ARCH_ATOMIC_IO_MODIFY
    +/*
    + * Generic atomic MMIO modify.
    + *
    + * Allows thread-safe access to registers shared by unrelated subsystems.
    + * The access is protected by a single MMIO-wide lock.
    + *
    + * Optimized variants can be implemented on a per-architecture basis.
    + */
    +static DEFINE_RAW_SPINLOCK(__io_lock);
    +void atomic_io_modify(void __iomem *reg, u32 mask, u32 set)
    +{
    + unsigned long flags;
    + u32 value;
    +
    + raw_spin_lock_irqsave(&__io_lock, flags);
    + value = readl(reg) & ~mask;
    + value |= (set & mask);
    + writel(value, reg);
    + raw_spin_unlock_irqrestore(&__io_lock, flags);
    +
    +}
    +EXPORT_SYMBOL(atomic_io_modify);
    +#endif
    --
    1.8.1.5


    \
     
     \ /
      Last update: 2013-08-24 17:41    [W:4.143 / U:0.972 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site