From 270dac35c26433d06a89150c51e75ca0181ca7e4 Mon Sep 17 00:00:00 2001 From: Jian Peng Date: Fri, 22 Apr 2011 23:58:10 -0700 Subject: [PATCH] libata: ahci_start_engine compliant to AHCI spec 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 Signed-off-by: Jeff Garzik --- drivers/ata/libahci.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c index d38c40fe4dd..ff9d832a163 100644 --- a/drivers/ata/libahci.c +++ b/drivers/ata/libahci.c @@ -561,6 +561,27 @@ 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); -- 2.20.1