Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 10 Jan 2002 16:52:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 10 Jan 2002 16:52:17 -0500 Received: from rj.SGI.COM ([204.94.215.100]:55726 "EHLO rj.sgi.com") by vger.kernel.org with ESMTP id ; Thu, 10 Jan 2002 16:51:40 -0500 Date: Thu, 10 Jan 2002 13:48:59 -0800 From: Jesse Barnes To: davem@redhat.com, ralf@uni-koblenz.de Cc: linux-kernel@vger.kernel.org Subject: memory-mapped i/o barrier Message-ID: <20020110134859.A729245@sgi.com> Mail-Followup-To: davem@redhat.com, ralf@uni-koblenz.de, linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.23i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Here's a copy of a patch I just got accepted into the 2.5 patch for ia64, and I'm wondering if you guys will accept something similar. On mips64, mmiob() could just be implemented as a 'sync', but I'm not sure how to do it (or if it's even necessary) on other platforms. Please let me know what you think. I wrote a small documentation file for the macro that appears at the top of the patch. Thanks, Jesse diff -Naur --exclude=*~ --exclude=TAGS linux-2.4.17-ia64/Documentation/mmio_barrier.txt linux-2.4.17-ia64-mmiob/Documentation/mmio_barrier.txt --- linux-2.4.17-ia64/Documentation/mmio_barrier.txt Wed Dec 31 16:00:00 1969 +++ linux-2.4.17-ia64-mmiob/Documentation/mmio_barrier.txt Tue Jan 8 15:57:37 2002 @@ -0,0 +1,15 @@ +On some platforms, so-called memory-mapped I/O is weakly ordered. For +example, the following might occur: + +CPU A writes 0x1 to Device #1 +CPU B writes 0x2 to Device #1 +Device #1 sees 0x2 +Device #1 sees 0x1 + +On such platforms, driver writers are responsible for guaranteeing that I/O +writes to memory-mapped addresses on their device arrive in the order +intended. The mmiob() macro is provided for this purpose. A typical use +of this macro might be immediately prior to the exit of a critical +section of code proteced by spinlocks. This would ensure that subsequent +writes to I/O space arrived only after all prior writes (much like a +typical memory barrier op, mb(), only with respect to I/O). diff -Naur --exclude=*~ --exclude=TAGS linux-2.4.17-ia64/arch/ia64/sn/kernel/sn1/iomv.c linux-2.4.17-ia64-mmiob/arch/ia64/sn/kernel/sn1/iomv.c --- linux-2.4.17-ia64/arch/ia64/sn/kernel/sn1/iomv.c Tue Jan 8 15:45:11 2002 +++ linux-2.4.17-ia64-mmiob/arch/ia64/sn/kernel/sn1/iomv.c Tue Jan 8 15:58:54 2002 @@ -9,6 +9,8 @@ #include #include #include +#include +#include static inline void * sn1_io_addr(unsigned long port) @@ -134,3 +136,9 @@ __ia64_mf_a(); } #endif /* SN1_IOPORTS */ + +void +sn_mmiob () +{ + PIO_FLUSH(); +} diff -Naur --exclude=*~ --exclude=TAGS linux-2.4.17-ia64/include/asm-ia64/io.h linux-2.4.17-ia64-mmiob/include/asm-ia64/io.h --- linux-2.4.17-ia64/include/asm-ia64/io.h Fri Nov 9 14:26:17 2001 +++ linux-2.4.17-ia64-mmiob/include/asm-ia64/io.h Wed Jan 9 10:53:46 2002 @@ -69,6 +69,21 @@ */ #define __ia64_mf_a() __asm__ __volatile__ ("mf.a" ::: "memory") +/** + * __ia64_mmiob - I/O space memory barrier + * + * Acts as a memory mapped I/O barrier for platforms that queue writes to + * I/O space. This ensures that subsequent writes to I/O space arrive after + * all previous writes. For most ia64 platforms, this is a simple + * 'mf.a' instruction. For other platforms, mmiob() may have to read + * a chipset register to ensure ordering. + */ +static inline void +__ia64_mmiob () +{ + __ia64_mf_a(); +} + static inline const unsigned long __ia64_get_io_port_base (void) { @@ -271,6 +286,7 @@ #define __outb platform_outb #define __outw platform_outw #define __outl platform_outl +#define __mmiob platform_mmiob #define inb __inb #define inw __inw @@ -284,6 +300,7 @@ #define outsb __outsb #define outsw __outsw #define outsl __outsl +#define mmiob __mmiob /* * The address passed to these functions are ioremap()ped already. diff -Naur --exclude=*~ --exclude=TAGS linux-2.4.17-ia64/include/asm-ia64/machvec.h linux-2.4.17-ia64-mmiob/include/asm-ia64/machvec.h --- linux-2.4.17-ia64/include/asm-ia64/machvec.h Tue Jan 8 15:45:11 2002 +++ linux-2.4.17-ia64-mmiob/include/asm-ia64/machvec.h Tue Jan 8 15:59:44 2002 @@ -60,6 +60,7 @@ typedef void ia64_mv_outb_t (unsigned char, unsigned long); typedef void ia64_mv_outw_t (unsigned short, unsigned long); typedef void ia64_mv_outl_t (unsigned int, unsigned long); +typedef void ia64_mv_mmiob_t (void); extern void machvec_noop (void); @@ -107,6 +108,7 @@ # define platform_outb ia64_mv.outb # define platform_outw ia64_mv.outw # define platform_outl ia64_mv.outl +# define platofrm_mmiob ia64_mv.mmiob # endif struct ia64_machine_vector { @@ -140,6 +142,7 @@ ia64_mv_outb_t *outb; ia64_mv_outw_t *outw; ia64_mv_outl_t *outl; + ia64_mv_mmiob_t *mmiob; }; #define MACHVEC_INIT(name) \ @@ -173,7 +176,8 @@ platform_inl, \ platform_outb, \ platform_outw, \ - platform_outl \ + platform_outl, \ + platform_mmiob \ } extern struct ia64_machine_vector ia64_mv; @@ -287,6 +291,9 @@ #endif #ifndef platform_outl # define platform_outl __ia64_outl +#endif +#ifndef platform_mmiob +# define platform_mmiob __ia64_mmiob #endif #endif /* _ASM_IA64_MACHVEC_H */ diff -Naur --exclude=*~ --exclude=TAGS linux-2.4.17-ia64/include/asm-ia64/machvec_sn1.h linux-2.4.17-ia64-mmiob/include/asm-ia64/machvec_sn1.h --- linux-2.4.17-ia64/include/asm-ia64/machvec_sn1.h Tue Jan 8 15:45:11 2002 +++ linux-2.4.17-ia64-mmiob/include/asm-ia64/machvec_sn1.h Tue Jan 8 15:45:54 2002 @@ -14,6 +14,7 @@ extern ia64_mv_outb_t sn1_outb; extern ia64_mv_outw_t sn1_outw; extern ia64_mv_outl_t sn1_outl; +extern ia64_mv_mmiob_t sn_mmiob; extern ia64_mv_pci_alloc_consistent sn1_pci_alloc_consistent; extern ia64_mv_pci_free_consistent sn1_pci_free_consistent; extern ia64_mv_pci_map_single sn1_pci_map_single; @@ -45,6 +46,7 @@ #define platform_outb sn1_outb #define platform_outw sn1_outw #define platform_outl sn1_outl +#define platform_mmiob sn_mmiob #define platform_pci_dma_init machvec_noop #define platform_pci_alloc_consistent sn1_pci_alloc_consistent #define platform_pci_free_consistent sn1_pci_free_consistent - 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/