Messages in this thread | | | Date | Wed, 28 Aug 2013 07:37:33 -0300 | From | Ezequiel Garcia <> | Subject | Re: [PATCH v4 1/4] lib: Introduce atomic MMIO modify |
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Linus,
Andrew suggested you might have opinions on this, so I'm cc'ing you. Since you'll probably want some better context, here it is:
http://lwn.net/Articles/564709/
On Sat, Aug 24, 2013 at 12:35:29PM -0300, Ezequiel Garcia wrote: > 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 >
-- Ezequiel García, Free Electrons Embedded Linux, Kernel and Android Engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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