From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: sata_sil24 with port multiplier Date: Sun, 23 Sep 2007 12:36:00 +0900 Message-ID: <46F5DF20.2010300@gmail.com> References: Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------040400080605020606050208" Return-path: Received: from rv-out-0910.google.com ([209.85.198.187]:15499 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751955AbXIWDgK (ORCPT ); Sat, 22 Sep 2007 23:36:10 -0400 Received: by rv-out-0910.google.com with SMTP id k20so1138104rvb for ; Sat, 22 Sep 2007 20:36:09 -0700 (PDT) In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jon Chelton Cc: linux-ide@vger.kernel.org This is a multi-part message in MIME format. --------------040400080605020606050208 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Please apply without the previous patch. Also, this is the correct version. -- tejun --------------040400080605020606050208 Content-Type: text/plain; name="fix-sata_sil24" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="fix-sata_sil24" [PATCH] sata_sil24: fix IRQ clearing race when PCIX_IRQ_WOC is used When PCIX_IRQ_WOC is used, sil24 has an inherent race condition between clearing IRQ pending and reading IRQ status. If IRQ pending is cleared after reading IRQ status, there's possibility of lost IRQ. If IRQ pending is cleared before reading IRQ status, spurious IRQs will occur. sata_sil24 till now cleared IRQ pending after reading IRQ status thus losing IRQs on machines where PCIX_IRQ_WOC was used. Reverse the order and ignore spurious IRQs if PCIX_IRQ_WOC. Signed-off-by: Tejun Heo --- This fixes a long-standing IRQ loss problem (and accompanying timeouts) on sata_sil24. drivers/ata/sata_sil24.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) Index: work/drivers/ata/sata_sil24.c =================================================================== --- work.orig/drivers/ata/sata_sil24.c +++ work/drivers/ata/sata_sil24.c @@ -889,6 +889,16 @@ static inline void sil24_host_intr(struc u32 slot_stat, qc_active; int rc; + /* If PCIX_IRQ_WOC, there's an inherent race window between + * clearing IRQ pending status and reading PORT_SLOT_STAT + * which may cause spurious interrupts afterwards. This is + * unavoidable and much better than losing interrupts which + * happens if IRQ pending is cleared after reading + * PORT_SLOT_STAT. + */ + if (ap->flags & SIL24_FLAG_PCIX_IRQ_WOC) + writel(PORT_IRQ_COMPLETE, port + PORT_IRQ_STAT); + slot_stat = readl(port + PORT_SLOT_STAT); if (unlikely(slot_stat & HOST_SSTAT_ATTN)) { @@ -896,9 +906,6 @@ static inline void sil24_host_intr(struc return; } - if (ap->flags & SIL24_FLAG_PCIX_IRQ_WOC) - writel(PORT_IRQ_COMPLETE, port + PORT_IRQ_STAT); - qc_active = slot_stat & ~HOST_SSTAT_ATTN; rc = ata_qc_complete_multiple(ap, qc_active, sil24_finish_qc); if (rc > 0) @@ -911,7 +918,8 @@ static inline void sil24_host_intr(struc return; } - if (ata_ratelimit()) + /* spurious interrupts are expected if PCIX_IRQ_WOC */ + if (!(ap->flags & SIL24_FLAG_PCIX_IRQ_WOC) && ata_ratelimit()) ata_port_printk(ap, KERN_INFO, "spurious interrupt " "(slot_stat 0x%x active_tag %d sactive 0x%x)\n", slot_stat, ap->link.active_tag, ap->link.sactive); --------------040400080605020606050208--