From bc18a46ad2a9c277ba25fcd662968af87bf3926d Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg@redhat.com>
Date: Sun, 28 Mar 2010 00:37:21 -0400
Subject: [PATCH] --- yaml --- r: 192592 b: refs/heads/master c:
 96d60303fd3336893a93565d58c4f1805a327061 h: refs/heads/master v: v3

---
 [refs]                      |  2 +-
 trunk/drivers/ata/libahci.c | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index a0c106b0bf08..0e5ada9307e8 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1c2a49f61785ebbcbfb481a2aab659020f0457f7
+refs/heads/master: 96d60303fd3336893a93565d58c4f1805a327061
diff --git a/trunk/drivers/ata/libahci.c b/trunk/drivers/ata/libahci.c
index 38e1b4e9ecf4..3f586ec84a3c 100644
--- a/trunk/drivers/ata/libahci.c
+++ b/trunk/drivers/ata/libahci.c
@@ -437,11 +437,29 @@ static int ahci_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val)
 	return -EINVAL;
 }
 
+static int ahci_is_device_present(void __iomem *port_mmio)
+{
+	u8 status = readl(port_mmio + PORT_TFDATA) & 0xff;
+
+	/* Make sure PxTFD.STS.BSY and PxTFD.STS.DRQ are 0 */
+	if (status & (ATA_BUSY | ATA_DRQ))
+		return 0;
+
+	/* Make sure PxSSTS.DET is 3h */
+	status = readl(port_mmio + PORT_SCR_STAT) & 0xf;
+	if (status != 3)
+		return 0;
+	return 1;
+}
+
 void ahci_start_engine(struct ata_port *ap)
 {
 	void __iomem *port_mmio = ahci_port_base(ap);
 	u32 tmp;
 
+	if (!ahci_is_device_present(port_mmio))
+		return;
+
 	/* start DMA */
 	tmp = readl(port_mmio + PORT_CMD);
 	tmp |= PORT_CMD_START;