IB/qib: Correct nfreectxts for multiple HCAs

The code that was recently introduced to report the number
of free contexts is flawed for multiple HCAs:

       /* Return the number of free user ports (contexts) available. */
       return scnprintf(buf, PAGE_SIZE, "%u\n", dd->cfgctxts -
                dd->first_user_ctxt - (u32)qib_stats.sps_ctxts);

The qib_stats is global to the module, not per HCA, so the code is broken
for multiple HCAs.

This patch adds a qib_devdata field, freectxts, that reflects the free
contexts for this HCA.

Signed-off-by: Mike Marciniszyn <mike.marciniszyn@qlogic.com>
Reviewed-by: Ram Vepa <ram.vepa@qlogic.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/qib/qib.h

@@ -807,6 +807,10 @@ struct qib_devdata {
 	 * supports, less gives more pio bufs/ctxt, etc.
 	 */
 	u32 cfgctxts;
+	/*
+	 * number of ctxts available for PSM open
+	 */
+	u32 freectxts;
 
 	/*
 	 * hint that we should update pioavailshadow before

drivers/infiniband/hw/qib/qib_file_ops.c

@@ -1284,6 +1284,7 @@ static int setup_ctxt(struct qib_pportdata *ppd, int ctxt,
 	strlcpy(rcd->comm, current->comm, sizeof(rcd->comm));
 	ctxt_fp(fp) = rcd;
 	qib_stats.sps_ctxts++;
+	dd->freectxts++;
 	ret = 0;
 	goto bail;
 
@@ -1792,6 +1793,7 @@ static int qib_close(struct inode *in, struct file *fp)
 		if (dd->pageshadow)
 			unlock_expected_tids(rcd);
 		qib_stats.sps_ctxts--;
+		dd->freectxts--;
 	}
 
 	mutex_unlock(&qib_mutex);

drivers/infiniband/hw/qib/qib_init.c

@@ -398,6 +398,7 @@ static void enable_chip(struct qib_devdata *dd)
 		if (rcd)
 			dd->f_rcvctrl(rcd->ppd, rcvmask, i);
 	}
+	dd->freectxts = dd->cfgctxts - dd->first_user_ctxt;
 }
 
 static void verify_interrupt(unsigned long opaque)

drivers/infiniband/hw/qib/qib_sysfs.c

@@ -515,8 +515,7 @@ static ssize_t show_nfreectxts(struct device *device,
 	struct qib_devdata *dd = dd_from_dev(dev);
 
 	/* Return the number of free user ports (contexts) available. */
-	return scnprintf(buf, PAGE_SIZE, "%u\n", dd->cfgctxts -
-		dd->first_user_ctxt - (u32)qib_stats.sps_ctxts);
+	return scnprintf(buf, PAGE_SIZE, "%u\n", dd->freectxts);
 }
 
 static ssize_t show_serial(struct device *device,