Revert "libata: ahci_start_engine compliant to AHCI spec"

This reverts commit 270dac35c26433d06a89150c51e75ca0181ca7e4.

The commits causes command timeouts on AC plug/unplug.  It isn't yet
clear why.  As the commit was for a single rather obscure controller,
revert the change for now.

The problem was reported and bisected by Gu Rui in bug#34692.

 https://bugzilla.kernel.org/show_bug.cgi?id=34692

Also, reported by Rafael and Michael in the following thread.

 http://thread.gmane.org/gmane.linux.kernel/1138771

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Gu Rui <chaos.proton@gmail.com>
Reported-by: Rafael J. Wysocki <rjw@sisk.pl>
Reported-by: Michael Leun <lkml20100708@newton.leun.net>
Cc: Jian Peng <jipeng2005@gmail.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 21 deletions

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index ff9d832a163d..d38c40fe4ddb 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -561,27 +561,6 @@ 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);