ata: pata_parport: add custom version of wait_after_reset

Some parallel adapters (e.g. EXP Computer MC-1285B EPP Cable) return
bogus values when there's no master device present. This can cause
reset to fail, preventing the lone slave device (such as EXP Computer
CD-865) from working.

Add custom version of wait_after_reset that ignores master failure when
a slave device is present. The custom version is also needed because
the generic ata_sff_wait_after_reset uses direct port I/O for slave
device detection.

Signed-off-by: Ondrej Zary <linux@zary.sk>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>

drivers/ata/pata_parport/pata_parport.c

@@ -80,6 +80,72 @@ static bool pata_parport_devchk(struct ata_port *ap, unsigned int device)
 	return (nsect == 0x55) && (lbal == 0xaa);
 }
 
+static int pata_parport_wait_after_reset(struct ata_link *link,
+					 unsigned int devmask,
+					 unsigned long deadline)
+{
+	struct ata_port *ap = link->ap;
+	struct pi_adapter *pi = ap->host->private_data;
+	unsigned int dev0 = devmask & (1 << 0);
+	unsigned int dev1 = devmask & (1 << 1);
+	int rc, ret = 0;
+
+	ata_msleep(ap, ATA_WAIT_AFTER_RESET);
+
+	/* always check readiness of the master device */
+	rc = ata_sff_wait_ready(link, deadline);
+	if (rc) {
+		/*
+		 * some adapters return bogus values if master device is not
+		 * present, so don't abort now if a slave device is present
+		 */
+		if (!dev1)
+			return rc;
+		ret = -ENODEV;
+	}
+
+	/*
+	 * if device 1 was found in ata_devchk, wait for register
+	 * access briefly, then wait for BSY to clear.
+	 */
+	if (dev1) {
+		int i;
+
+		pata_parport_dev_select(ap, 1);
+
+		/*
+		 * Wait for register access.  Some ATAPI devices fail
+		 * to set nsect/lbal after reset, so don't waste too
+		 * much time on it.  We're gonna wait for !BSY anyway.
+		 */
+		for (i = 0; i < 2; i++) {
+			u8 nsect, lbal;
+
+			nsect = pi->proto->read_regr(pi, 0, ATA_REG_NSECT);
+			lbal = pi->proto->read_regr(pi, 0, ATA_REG_LBAL);
+			if (nsect == 1 && lbal == 1)
+				break;
+			/* give drive a breather */
+			ata_msleep(ap, 50);
+		}
+
+		rc = ata_sff_wait_ready(link, deadline);
+		if (rc) {
+			if (rc != -ENODEV)
+				return rc;
+			ret = rc;
+		}
+	}
+
+	pata_parport_dev_select(ap, 0);
+	if (dev1)
+		pata_parport_dev_select(ap, 1);
+	if (dev0)
+		pata_parport_dev_select(ap, 0);
+
+	return ret;
+}
+
 static int pata_parport_bus_softreset(struct ata_port *ap, unsigned int devmask,
 				      unsigned long deadline)
 {
@@ -94,7 +160,7 @@ static int pata_parport_bus_softreset(struct ata_port *ap, unsigned int devmask,
 	ap->last_ctl = ap->ctl;
 
 	/* wait the port to become ready */
-	return ata_sff_wait_after_reset(&ap->link, devmask, deadline);
+	return pata_parport_wait_after_reset(&ap->link, devmask, deadline);
 }
 
 static int pata_parport_softreset(struct ata_link *link, unsigned int *classes,