From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jian Peng" Subject: [PATCH 1/1] libata: ahci_start_engine compliant to AHCI spec Date: Fri, 22 Apr 2011 23:58:10 -0700 Message-ID: <1303541890-14528-1-git-send-email-jipeng2005@gmail.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from mms2.broadcom.com ([216.31.210.18]:4611 "EHLO mms2.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751033Ab1DWG62 (ORCPT ); Sat, 23 Apr 2011 02:58:28 -0400 Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik , Tejun Heo Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, Jian Peng At the end of section 10.1 of AHCI spec (rev 1.3), it states Software shall not set PxCMD.ST to 1 until it is determined that a functoinal device is present on the port as determined by PxTFD.STS.BSY=0, PxTFD.STS.DRQ=0 and PxSSTS.DET=3h Even though most AHCI host controller works without this check, specific controller will fail under this condition. Signed-off-by: Jian Peng --- drivers/ata/libahci.c | 21 +++++++++++++++++++++ 1 files changed, 21 insertions(+), 0 deletions(-) diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c index 26d4523..83ed544 100644 --- a/drivers/ata/libahci.c +++ b/drivers/ata/libahci.c @@ -539,6 +539,27 @@ void ahci_start_engine(struct ata_port *ap) { void __iomem *port_mmio = ahci_port_base(ap); u32 tmp; + u8 status; + + status = readl(port_mmio + PORT_TFDATA) & 0xFF; + + /* + * At end of section 10.1 of AHCI spec (rev 1.3), it states + * Software shall not set PxCMD.ST to 1 until it is determined + * that a functoinal device is present on the port as determined by + * PxTFD.STS.BSY=0, PxTFD.STS.DRQ=0 and PxSSTS.DET=3h + * + * Even though most AHCI host controllers work without this check, + * specific controller will fail under this condition + */ + if (status & (ATA_BUSY | ATA_DRQ)) + return; + else { + ahci_scr_read(&ap->link, SCR_STATUS, &tmp); + + if ((tmp & 0xf) != 0x3) + return; + } /* start DMA */ tmp = readl(port_mmio + PORT_CMD); -- 1.7.4.1