sata_nv: delay on switching between NCQ and non-NCQ commands

This patch appears to solve some problems with commands timing out in cases where an NCQ command is immediately followed by a non-NCQ command (or possibly vice versa). This is a rather ugly solution, but until we know more about why this is needed, this is about all we can do.

@@ -219,6 +219,7 @@

	void __iomem *		gen_block;
	void __iomem *		notifier_clear_block;
	u8			flags;

+ int last_issue_ncq;
};

struct nv_host_priv {
@@ -1260,6 +1261,7 @@

{
	struct nv_adma_port_priv *pp = qc->ap->private_data;
	void __iomem *mmio = pp->ctl_block;

+ int curr_ncq = (qc->tf.protocol == ATA_PROT_NCQ);

	VPRINTK("ENTER\n");

@@ -1274,6 +1276,14 @@

	/* write append register, command tag in lower 8 bits
	   and (number of cpbs to append -1) in top 8 bits */
	wmb();

+
+ if(curr_ncq != pp->last_issue_ncq) {
+ /* Seems to need some delay before switching between NCQ and non-NCQ
+ commands, else we get command timeouts and such. */
+ udelay(20);
+ pp->last_issue_ncq = curr_ncq;
+ }
+

	writew(qc->tag, mmio + NV_ADMA_APPEND);

	DPRINTK("Issued tag %u\n",qc->tag);

applied