From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 19 May 2009 03:37:58 +0100 (BST) Received: from [222.92.8.141] ([222.92.8.141]:56908 "EHLO lemote.com" rhost-flags-FAIL-FAIL-OK-OK) by ftp.linux-mips.org with ESMTP id S20024551AbZESChv (ORCPT ); Tue, 19 May 2009 03:37:51 +0100 Received: from localhost (localhost [127.0.0.1]) by lemote.com (Postfix) with ESMTP id 991453404A; Tue, 19 May 2009 10:33:00 +0800 (CST) X-Virus-Scanned: Debian amavisd-new at lemote.com Received: from lemote.com ([127.0.0.1]) by localhost (www.lemote.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id B28txt4Goztb; Tue, 19 May 2009 10:32:55 +0800 (CST) Received: from [172.16.2.16] (unknown [222.92.8.142]) by lemote.com (Postfix) with ESMTP id 6DD6731C979; Tue, 19 May 2009 10:32:55 +0800 (CST) Subject: Re: [PATCH 26/30] loongson: flush irq write operation From: yanh Reply-To: yanh@lemote.com To: Ralf Baechle Cc: Wu Zhangjin , linux-mips@linux-mips.org, Arnaud Patard , loongson-dev@googlegroups.com, zhangfx@lemote.com, Philippe Vachon , Zhang Le , Erwan Lerale In-Reply-To: <20090518163603.GA22779@linux-mips.org> References: <1242426527.10164.174.camel@falcon> <20090518163603.GA22779@linux-mips.org> Content-Type: text/plain; charset="UTF-8" Date: Tue, 19 May 2009 10:37:17 +0800 Message-Id: <1242700637.4382.21.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 (2.24.1-2.fc10) Content-Transfer-Encoding: 8bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 22810 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: yanh@lemote.com Precedence: bulk X-list: linux-mips 在 2009-05-18一的 17:36 +0100，Ralf Baechle写道： > On Sat, May 16, 2009 at 06:28:47AM +0800, Wu Zhangjin wrote: > > > read back after write, otherwise, there will be many spurious irqs from > > it > > --- > > arch/mips/kernel/i8259.c | 5 +++++ > > arch/mips/loongson/common/bonito-irq.c | 4 ++++ > > 2 files changed, 9 insertions(+), 0 deletions(-) > > > > diff --git a/arch/mips/kernel/i8259.c b/arch/mips/kernel/i8259.c > > index 413bd1d..f7c3a2b 100644 > > --- a/arch/mips/kernel/i8259.c > > +++ b/arch/mips/kernel/i8259.c > > @@ -175,12 +175,17 @@ handle_real_irq: > > if (irq & 8) { > > inb(PIC_SLAVE_IMR); /* DUMMY - (do we need this?) */ > > outb(cached_slave_mask, PIC_SLAVE_IMR); > > + inb(PIC_SLAVE_IMR); > > outb(0x60+(irq&7), PIC_SLAVE_CMD);/* 'Specific EOI' to slave */ > > + inb(PIC_SLAVE_CMD); > > outb(0x60+PIC_CASCADE_IR, PIC_MASTER_CMD); /* 'Specific EOI' to > > master-IRQ2 */ > > + inb(PIC_MASTER_CMD); > > } else { > > inb(PIC_MASTER_IMR); /* DUMMY - (do we need this?) */ > > outb(cached_master_mask, PIC_MASTER_IMR); > > + inb(PIC_SLAVE_IMR); > > outb(0x60+irq, PIC_MASTER_CMD); /* 'Specific EOI to master */ > > + inb(PIC_MASTER_CMD); > > } > > smtc_im_ack_irq(irq); > > spin_unlock_irqrestore(&i8259A_lock, flags); > > The semantic of inX() / outX() is defined by the x86 architecture which > forbids posting I/O port writes. In short I think this one is papering > over a bug in the outX() implementation. Yes, the outX should do a delayed write, however it does not. So our solution is making a read to flush the write. > > I'm ok with the bonito part of this patch. > > Ralf