Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755686Ab3HXUtS (ORCPT ); Sat, 24 Aug 2013 16:49:18 -0400 Received: from top.free-electrons.com ([176.31.233.9]:55148 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755518Ab3HXUtR (ORCPT ); Sat, 24 Aug 2013 16:49:17 -0400 Date: Sat, 24 Aug 2013 17:49:13 -0300 From: Ezequiel Garcia To: Richard Weinberger Cc: richard -rw- weinberger , "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: <20130824204912.GA9456@localhost> References: <1377358532-23802-1-git-send-email-ezequiel.garcia@free-electrons.com> <1377358532-23802-2-git-send-email-ezequiel.garcia@free-electrons.com> <20130824195858.GA5957@localhost> <52191916.4080600@nod.at> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <52191916.4080600@nod.at> 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: 4379 Lines: 107 On Sat, Aug 24, 2013 at 10:35:34PM +0200, Richard Weinberger wrote: > Am 24.08.2013 21:58, schrieb Ezequiel Garcia: > > 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/ ? > > As the kernel is GPL it is the default case to mark new things as GPL symbols. > If your new feature is a core feature which is used by mostly everyone, EXPORT_SYMBOL() > is appropriate. > I.e. having kmalloc() and friends EXPORT_SYMBOL_GPL() would be a bad idea. :) > EXPORT_SYMBOL() seems to be often used in lib/ because most lib/ things are core features. > In that case, EXPORT_SYMBOL is certainly the most appropriate one, for the reasons you stated above. -- 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/