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Commit 22fe9446 authored by Tejun Heo's avatar Tejun Heo Committed by Linus Torvalds
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Revert "libata: ahci_start_engine compliant to AHCI spec" 

This reverts commit 270dac35.

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: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarGu Rui <chaos.proton@gmail.com>
Reported-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
Reported-by: default avatarMichael Leun <lkml20100708@newton.leun.net>
Cc: Jian Peng <jipeng2005@gmail.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ddb503b4

drivers/ata/libahci.c

+0 −21
Original line number Original line Diff line number Diff line
@@ -561,27 +561,6 @@ void ahci_start_engine(struct ata_port *ap) 
{

{

	void __iomem *port_mmio = ahci_port_base(ap);

	void __iomem *port_mmio = ahci_port_base(ap);

	u32 tmp;

	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 */

	/* start DMA */

	tmp = readl(port_mmio + PORT_CMD);

	tmp = readl(port_mmio + PORT_CMD);