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>

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index ff9d832a163de8442c2adc1d8fa18be75ec4f417..d38c40fe4ddbfeace9bb1460505aac4add9d23f1 100644 (file)
--- 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);