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Revert "libata: ahci_start_engine compliant to AHCI spec" 

This reverts commit 270dac35c2.

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>
This commit is contained in:
Tejun Heo 2011-05-14 12:28:04 +02:00 committed by Linus Torvalds
parent ddb503b429
commit 22fe9446e8
1 changed files with 0 additions and 21 deletions
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21
drivers/ata/libahci.c
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@ -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);