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: Tue, 19 Apr 2011 14:44:59 -0700 Message-ID: <1303249499-11557-1-git-send-email-jipeng2005@gmail.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Sender: linux-kernel-owner@vger.kernel.org To: Jeff Garzik , Tejun Heo Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, Jian Peng List-Id: linux-ide@vger.kernel.org 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 additional check, specific controller will fail without this. Signed-off-by: Jian Peng --- drivers/ata/libahci.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c index 26d4523..39e0698 100644 --- a/drivers/ata/libahci.c +++ b/drivers/ata/libahci.c @@ -539,6 +539,12 @@ void ahci_start_engine(struct ata_port *ap) { void __iomem *port_mmio = ahci_port_base(ap); u32 tmp; + u8 status = readl(port_mmio + PORT_TFDATA) & 0xFF; + + if (status & (ATA_BUSY | ATA_DRQ) || + ahci_scr_read(&ap->link, SCR_STATUS, &tmp) || + (tmp & 0x0f) != 0x03) + return; /* start DMA */ tmp = readl(port_mmio + PORT_CMD); -- 1.7.4.1