Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755744Ab3HXT7F (ORCPT ); Sat, 24 Aug 2013 15:59:05 -0400 Received: from top.free-electrons.com ([176.31.233.9]:55078 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755614Ab3HXT7E (ORCPT ); Sat, 24 Aug 2013 15:59:04 -0400 Date: Sat, 24 Aug 2013 16:58:59 -0300 From: Ezequiel Garcia To: richard -rw- weinberger Cc: "linux-arm-kernel@lists.infradead.org" , LKML , Thomas Petazzoni , Gregory Clement , Lior Amsalem , Baruch Siach , Will Deacon , Sebastian Hesselbarth , Russell King , Catalin Marinas Subject: Re: [PATCH v4 1/4] lib: Introduce atomic MMIO modify Message-ID: <20130824195858.GA5957@localhost> References: <1377358532-23802-1-git-send-email-ezequiel.garcia@free-electrons.com> <1377358532-23802-2-git-send-email-ezequiel.garcia@free-electrons.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3704 Lines: 102 On Sat, Aug 24, 2013 at 08:27:10PM +0200, richard -rw- weinberger wrote: > On Sat, Aug 24, 2013 at 5:35 PM, 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 > > --- > > 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 > > +#include > > + > > +#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); > > Why not the default case EXPORT_SYMBOL_GPL()? > Because I copy-pasted the export from some other lib/.. :-) Mind explaining me the difference, why you say _GPL it's the default, and why EXPORT_SYMBOL is more frequently used in lib/ ? $ git grep EXPORT_SYMBOL lib/ | wc -l 598 $ git grep EXPORT_SYMBOL_GPL lib/ | wc -l 117 Thanks! -- 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/