libata: Add a per-host flag to opt-in into parallel port probes

This patch adds a per host flag that allows drivers to opt in into
having its busses scanned in parallel.

Drivers that do not set this flag get their ports scanned in
the "original" sequence.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/ata/ahci.c

@@ -2660,6 +2660,9 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	host->iomap = pcim_iomap_table(pdev);
 	host->private_data = hpriv;
 
+	if (!(hpriv->cap & HOST_CAP_SSS))
+		host->flags |= ATA_HOST_PARALLEL_SCAN;
+
 	if (pi.flags & ATA_FLAG_EM)
 		ahci_reset_em(host);
 

drivers/ata/libata-core.c

@@ -5920,6 +5920,15 @@ static void async_port_probe(void *data, async_cookie_t cookie)
 {
 	int rc;
 	struct ata_port *ap = data;
+
+	/*
+	 * If we're not allowed to scan this host in parallel,
+	 * we need to wait until all previous scans have completed
+	 * before going further.
+	 */
+	if (!(ap->host->flags & ATA_HOST_PARALLEL_SCAN))
+		async_synchronize_cookie(cookie);
+
 	/* probe */
 	if (ap->ops->error_handler) {
 		struct ata_eh_info *ehi = &ap->link.eh_info;

include/linux/libata.h

@@ -239,6 +239,7 @@ enum {
 	/* host set flags */
 	ATA_HOST_SIMPLEX	= (1 << 0),	/* Host is simplex, one DMA channel per host only */
 	ATA_HOST_STARTED	= (1 << 1),	/* Host started */
+	ATA_HOST_PARALLEL_SCAN	= (1 << 2),	/* Ports on this host can be scanned in parallel */
 
 	/* bits 24:31 of host->flags are reserved for LLD specific flags */