[libata] sata_mv: Add a new mv_sff_check_status() function to sata_mv. This is necessary for use with the upcoming "mv_qc_issue_fis()" patch, but is being added separately here for easier code review.

When using command issue via the "mv_qc_issue_fis()" mechanism,
the initial ATA_BUSY bit does not show in the ATA status (shadow) register.
This can confuse libata! So here we add a hook to fake ATA_BUSY
for that situation, until the first time a BUSY, DRQ, or ERR bit is seen.

Signed-off-by: Mark Lord <[e-mail]>
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/ata/sata_mv.c

···
 	MV_PP_FLAG_NCQ_EN	= (1 << 1),	/* is EDMA set up for NCQ? */
 	MV_PP_FLAG_FBS_EN	= (1 << 2),	/* is EDMA set up for FBS? */
 	MV_PP_FLAG_DELAYED_EH	= (1 << 3),	/* delayed dev err handling */
+	MV_PP_FLAG_FAKE_ATA_BUSY = (1 << 4),	/* ignore initial ATA_DRDY */
 };
 
 #define IS_GEN_I(hpriv) ((hpriv)->hp_flags & MV_HP_GEN_I)
···
 static void mv_bmdma_start(struct ata_queued_cmd *qc);
 static void mv_bmdma_stop(struct ata_queued_cmd *qc);
 static u8   mv_bmdma_status(struct ata_port *ap);
+static u8 mv_sff_check_status(struct ata_port *ap);
 
 /* .sg_tablesize is (MV_MAX_SG_CT / 2) in the structures below
  * because we have to allow room for worst case splitting of
···
 	.softreset		= mv_softreset,
 	.error_handler		= mv_pmp_error_handler,
 
+ 	.sff_check_status	= mv_sff_check_status,
 	.sff_irq_clear		= mv_sff_irq_clear,
 	.check_atapi_dma	= mv_check_atapi_dma,
 	.bmdma_setup		= mv_bmdma_setup,
···
 
 	/* set up non-NCQ EDMA configuration */
 	cfg = EDMA_CFG_Q_DEPTH;		/* always 0x1f for *all* chips */
-	pp->pp_flags &= ~(MV_PP_FLAG_FBS_EN | MV_PP_FLAG_NCQ_EN);
+	pp->pp_flags &=
+	  ~(MV_PP_FLAG_FBS_EN | MV_PP_FLAG_NCQ_EN | MV_PP_FLAG_FAKE_ATA_BUSY);
 
 	if (IS_GEN_I(hpriv))
 		cfg |= (1 << 8);	/* enab config burst size mask */
···
 }
 
 /**
+ *	mv_sff_check_status - fetch device status, if valid
+ *	@ap: ATA port to fetch status from
+ *
+ *	When using command issue via mv_qc_issue_fis(),
+ *	the initial ATA_BUSY state does not show up in the
+ *	ATA status (shadow) register.  This can confuse libata!
+ *
+ *	So we have a hook here to fake ATA_BUSY for that situation,
+ *	until the first time a BUSY, DRQ, or ERR bit is seen.
+ *
+ *	The rest of the time, it simply returns the ATA status register.
+ */
+static u8 mv_sff_check_status(struct ata_port *ap)
+{
+	u8 stat = ioread8(ap->ioaddr.status_addr);
+	struct mv_port_priv *pp = ap->private_data;
+
+	if (pp->pp_flags & MV_PP_FLAG_FAKE_ATA_BUSY) {
+		if (stat & (ATA_BUSY | ATA_DRQ | ATA_ERR))
+			pp->pp_flags &= ~MV_PP_FLAG_FAKE_ATA_BUSY;
+		else
+			stat = ATA_BUSY;
+	}
+	return stat;
+}
+
+/**
  *      mv_qc_issue - Initiate a command to the host
  *      @qc: queued command to start
  *
···
 	struct mv_port_priv *pp = ap->private_data;
 	u32 in_index;
 	unsigned int port_irqs;
+
+	pp->pp_flags &= ~MV_PP_FLAG_FAKE_ATA_BUSY; /* paranoia */
 
 	switch (qc->tf.protocol) {
 	case ATA_PROT_DMA:
···
 
 	mv_reset_channel(hpriv, mmio, ap->port_no);
 	pp->pp_flags &= ~MV_PP_FLAG_EDMA_EN;
+	pp->pp_flags &=
+	  ~(MV_PP_FLAG_FBS_EN | MV_PP_FLAG_NCQ_EN | MV_PP_FLAG_FAKE_ATA_BUSY);
 
 	/* Workaround for errata FEr SATA#10 (part 2) */
 	do {