Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755891Ab3HXUxr (ORCPT ); Sat, 24 Aug 2013 16:53:47 -0400 Received: from b.ns.miles-group.at ([95.130.255.144]:1660 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755761Ab3HXUxq (ORCPT ); Sat, 24 Aug 2013 16:53:46 -0400 Message-ID: <52191D57.3030906@nod.at> Date: Sat, 24 Aug 2013 22:53:43 +0200 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: Ezequiel Garcia 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 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> <20130824204912.GA9456@localhost> In-Reply-To: <20130824204912.GA9456@localhost> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4414 Lines: 111 Am 24.08.2013 22:49, schrieb Ezequiel Garcia: > 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. Okay, did not realize that your feature is that fundamental. :-) Thanks, //richard -- 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/