libahci: fix result_tf handling after an ATA PIO data-in command

ATA devices don't send D2H Reg FIS after an successful ATA PIO data-in
command. The host is supposed to take the TF and E_Status of the
preceding PIO Setup FIS. Update ahci_qc_fill_rtf() such that it takes
TF + E_Status from PIO Setup FIS after a successful ATA PIO data-in
command.

Without this patch, result_tf for such a command is filled with the
content of the previous D2H Reg FIS which belongs to a previous
command, which can make the command incorrectly seen as failed.

* Patch updated to grab the whole TF + E_Status from PIO Setup FIS
instead of just E_Status as suggested by Robert Hancock.

Signed-off-by: Tejun Heo <[e-mail]>
Reported-by: Mark Lord <[e-mail]>
Cc: Robert Hancock <[e-mail]>
Cc: [e-mail]
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/ata/ahci.h

···
 	AHCI_CMD_RESET		= (1 << 8),
 	AHCI_CMD_CLR_BUSY	= (1 << 10),
 
+	RX_FIS_PIO_SETUP	= 0x20,	/* offset of PIO Setup FIS data */
 	RX_FIS_D2H_REG		= 0x40,	/* offset of D2H Register FIS data */
 	RX_FIS_SDB		= 0x58, /* offset of SDB FIS data */
 	RX_FIS_UNK		= 0x60, /* offset of Unknown FIS data */

drivers/ata/libahci.c

···
 static bool ahci_qc_fill_rtf(struct ata_queued_cmd *qc)
 {
 	struct ahci_port_priv *pp = qc->ap->private_data;
-	u8 *d2h_fis = pp->rx_fis + RX_FIS_D2H_REG;
+	u8 *rx_fis = pp->rx_fis;
 
 	if (pp->fbs_enabled)
-		d2h_fis += qc->dev->link->pmp * AHCI_RX_FIS_SZ;
+		rx_fis += qc->dev->link->pmp * AHCI_RX_FIS_SZ;
 
-	ata_tf_from_fis(d2h_fis, &qc->result_tf);
+	/*
+	 * After a successful execution of an ATA PIO data-in command,
+	 * the device doesn't send D2H Reg FIS to update the TF and
+	 * the host should take TF and E_Status from the preceding PIO
+	 * Setup FIS.
+	 */
+	if (qc->tf.protocol == ATA_PROT_PIO && qc->dma_dir == DMA_FROM_DEVICE &&
+	    !(qc->flags & ATA_QCFLAG_FAILED)) {
+		ata_tf_from_fis(rx_fis + RX_FIS_PIO_SETUP, &qc->result_tf);
+		qc->result_tf.command = (rx_fis + RX_FIS_PIO_SETUP)[15];
+	} else
+		ata_tf_from_fis(rx_fis + RX_FIS_D2H_REG, &qc->result_tf);
+
 	return true;
 }