From 270dac35c26433d06a89150c51e75ca0181ca7e4 Mon Sep 17 00:00:00 2001
From: Jian Peng <jipeng2005@gmail.com>
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 <jipeng2005@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
---
drivers/ata/libahci.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index d38c40fe4ddbf..ff9d832a163de 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);
--
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