Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755264Ab3HXPfq (ORCPT ); Sat, 24 Aug 2013 11:35:46 -0400 Received: from top.free-electrons.com ([176.31.233.9]:54614 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754323Ab3HXPfo (ORCPT ); Sat, 24 Aug 2013 11:35:44 -0400 From: Ezequiel Garcia To: , Cc: Thomas Petazzoni , Gregory Clement , Lior Amsalem , Baruch Siach , Will Deacon , Sebastian Hesselbarth , Russell King , Catalin Marinas , Ezequiel Garcia Subject: [PATCH v4 1/4] lib: Introduce atomic MMIO modify Date: Sat, 24 Aug 2013 12:35:29 -0300 Message-Id: <1377358532-23802-2-git-send-email-ezequiel.garcia@free-electrons.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1377358532-23802-1-git-send-email-ezequiel.garcia@free-electrons.com> References: <1377358532-23802-1-git-send-email-ezequiel.garcia@free-electrons.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2740 Lines: 84 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); +#endif -- 1.8.1.5 -- 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/