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| author | Jian Peng <jipeng2005@gmail.com> | 2011-04-22 23:58:10 -0700 |
|---|---|---|
| committer | Jeff Garzik <jgarzik@pobox.com> | 2011-04-24 11:35:40 -0400 |
| commit | 270dac35c26433d06a89150c51e75ca0181ca7e4 (patch) | |
| tree | 187f95b21867318d77b768e1e8be27b0894c239b | |
| parent | 792d37af35386466cf5dda51d6b710fa1dd9aad1 (diff) | |
| download | lwn-270dac35c26433d06a89150c51e75ca0181ca7e4.tar.gz lwn-270dac35c26433d06a89150c51e75ca0181ca7e4.zip | |
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 <jipeng2005@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
| -rw-r--r-- | 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 d38c40fe4ddb..ff9d832a163d 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); |