IB/ipath: Verify host bus bandwidth to chip will not limit performance

There have been a number of issues where host bandwidth via HT or PCIe
to the InfiniPath chip has been limited in some fashion (BIOS,
configuration, etc.), resulting in user confusion.  This check gives a
clear warning that something is wrong and needs to be resolved.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 86 insertions, 0 deletions

diff --git a/drivers/infiniband/hw/ipath/ipath_driver.c b/drivers/infiniband/hw/ipath/ipath_driver.c
index 6ccba365a24..5248f57fe19 100644
--- a/drivers/infiniband/hw/ipath/ipath_driver.c
+++ b/drivers/infiniband/hw/ipath/ipath_driver.c
@@ -34,6 +34,7 @@
 #include <linux/spinlock.h>
 #include <linux/idr.h>
 #include <linux/pci.h>
+#include <linux/io.h>
 #include <linux/delay.h>
 #include <linux/netdevice.h>
 #include <linux/vmalloc.h>
@@ -280,6 +281,89 @@ void __attribute__((weak)) ipath_disable_wc(struct ipath_devdata *dd)
 {
 }
 
+/*
+ * Perform a PIO buffer bandwidth write test, to verify proper system
+ * configuration.  Even when all the setup calls work, occasionally
+ * BIOS or other issues can prevent write combining from working, or
+ * can cause other bandwidth problems to the chip.
+ *
+ * This test simply writes the same buffer over and over again, and
+ * measures close to the peak bandwidth to the chip (not testing
+ * data bandwidth to the wire).   On chips that use an address-based
+ * trigger to send packets to the wire, this is easy.  On chips that
+ * use a count to trigger, we want to make sure that the packet doesn't
+ * go out on the wire, or trigger flow control checks.
+ */
+static void ipath_verify_pioperf(struct ipath_devdata *dd)
+{
+        u32 pbnum, cnt, lcnt;
+        u32 __iomem *piobuf;
+        u32 *addr;
+        u64 msecs, emsecs;
+
+        piobuf = ipath_getpiobuf(dd, &pbnum);
+        if (!piobuf) {
+                dev_info(&dd->pcidev->dev,
+                        "No PIObufs for checking perf, skipping\n");
+                return;
+        }
+
+        /*
+         * Enough to give us a reasonable test, less than piobuf size, and
+         * likely multiple of store buffer length.
+         */
+        cnt = 1024;
+
+        addr = vmalloc(cnt);
+        if (!addr) {
+                dev_info(&dd->pcidev->dev,
+                        "Couldn't get memory for checking PIO perf,"
+                        " skipping\n");
+                goto done;
+        }
+
+        preempt_disable();  /* we want reasonably accurate elapsed time */
+        msecs = 1 + jiffies_to_msecs(jiffies);
+        for (lcnt = 0; lcnt < 10000U; lcnt++) {
+                /* wait until we cross msec boundary */
+                if (jiffies_to_msecs(jiffies) >= msecs)
+                        break;
+                udelay(1);
+        }
+
+        writeq(0, piobuf); /* length 0, no dwords actually sent */
+        ipath_flush_wc();
+
+        /*
+         * this is only roughly accurate, since even with preempt we
+         * still take interrupts that could take a while.   Running for
+         * >= 5 msec seems to get us "close enough" to accurate values
+         */
+        msecs = jiffies_to_msecs(jiffies);
+        for (emsecs = lcnt = 0; emsecs <= 5UL; lcnt++) {
+                __iowrite32_copy(piobuf + 64, addr, cnt >> 2);
+                emsecs = jiffies_to_msecs(jiffies) - msecs;
+        }
+
+        /* 1 GiB/sec, slightly over IB SDR line rate */
+        if (lcnt < (emsecs * 1024U))
+                ipath_dev_err(dd,
+                        "Performance problem: bandwidth to PIO buffers is "
+                        "only %u MiB/sec\n",
+                        lcnt / (u32) emsecs);
+        else
+                ipath_dbg("PIO buffer bandwidth %u MiB/sec is OK\n",
+                        lcnt / (u32) emsecs);
+
+        preempt_enable();
+
+        vfree(addr);
+
+done:
+        /* disarm piobuf, so it's available again */
+        ipath_disarm_piobufs(dd, pbnum, 1);
+}
+
 static int __devinit ipath_init_one(struct pci_dev *pdev,
                                     const struct pci_device_id *ent)
 {
@@ -515,6 +599,8 @@ static int __devinit ipath_init_one(struct pci_dev *pdev,
                 ret = 0;
         }
 
+        ipath_verify_pioperf(dd);
+
         ipath_device_create_group(&pdev->dev, dd);
         ipathfs_add_device(dd);
         ipath_user_add(dd);