According to the AHCI spec, you should not set PxCMD.ST unless
a functional device is present, as determined by PxTFD.STS.BSY=0,
PxTFD.STS.DRQ=0, and PxSSTS.DET = 3.
Signed-off-by: Kristen Carlson Accardi <[EMAIL PROTECTED]>
Index: linux-2.6.25-rc3/drivers/ata/ahci.c
===================================================================
--- linux-2.6.25-rc3.orig/drivers/ata/ahci.c
+++ linux-2.6.25-rc3/drivers/ata/ahci.c
@@ -783,11 +783,40 @@ static int ahci_scr_write(struct ata_por
return -EINVAL;
}
+static int ahci_is_device_present(struct ata_port *ap)
+{
+ void __iomem *port_mmio = ahci_port_base(ap);
+ u8 status;
+
+ /* Make sure PxTFD.STS.BSY and PxTFD.STS.DRQ are 0 */
+ status = ahci_check_status(ap);
+ if (status & (ATA_BUSY | ATA_DRQ))
+ return 0;
+
+ /* Make sure PxSSTS.DET is 3h */
+ status = readl(port_mmio + PORT_SCR_STAT);
+ status &= 0xf;
+ if ((status & 0xf) != 3)
+ return 0;
+ return 1;
+}
+
static void ahci_start_engine(struct ata_port *ap)
{
void __iomem *port_mmio = ahci_port_base(ap);
u32 tmp;
+ /*
+ * See AHCI specification 1.2 section 10.1.2
+ *
+ * Software shall not set PxCMD.ST to '1' until it is
+ * determined that a functional device is present on
+ * the port, as determined by PxTFD.STS.BSY = '0',
+ * PxTFD.STS.DRQ = '0', PxSSTS.DET = 3h
+ */
+ if (!ahci_is_device_present(ap))
+ return;
+
/* start DMA */
tmp = readl(port_mmio + PORT_CMD);
tmp |= PORT_CMD_START;
--
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