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Commit 270dac35 authored by Jian Peng's avatar Jian Peng Committed by Jeff Garzik
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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: default avatarJian Peng <jipeng2005@gmail.com>
Signed-off-by: default avatarJeff Garzik <jgarzik@pobox.com>
parent 792d37af

drivers/ata/libahci.c

+21 −0
Original line number Diff line number Diff line
@@ -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);