PCI: Remove MRRS modification from MPS setting code

Modifying the Maximum Read Request Size to 0 (value of 128Bytes) has
massive negative ramifications on some devices.  Without knowing which
devices have this issue, do not modify from the default value when
walking the PCI-E bus in pcie_bus_safe mode.  Also, make pcie_bus_safe
the default procedure.

Tested-by: Sven Schnelle <svens@stackframe.org>
Tested-by: Simon Kirby <sim@hostway.ca>
Tested-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Reported-and-tested-by: Niels Ole Salscheider <niels_ole@salscheider-online.de>
References: https://bugzilla.kernel.org/show_bug.cgi?id=42162
Signed-off-by: Jon Mason <mason@myri.com>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 23 insertions, 20 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 0ce67423a0a3..4e84fd4a4312 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -77,7 +77,7 @@ unsigned long pci_cardbus_mem_size = DEFAULT_CARDBUS_MEM_SIZE;
 unsigned long pci_hotplug_io_size  = DEFAULT_HOTPLUG_IO_SIZE;
 unsigned long pci_hotplug_mem_size = DEFAULT_HOTPLUG_MEM_SIZE;
 
-enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_PERFORMANCE;
+enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_SAFE;
 
 /*
  * The default CLS is used if arch didn't set CLS explicitly and not
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 0820fc1544e8..b1187ff31d89 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1396,34 +1396,37 @@ static void pcie_write_mps(struct pci_dev *dev, int mps)
 
 static void pcie_write_mrrs(struct pci_dev *dev, int mps)
 {
-        int rc, mrrs;
+        int rc, mrrs, dev_mpss;
 
-        if (pcie_bus_config == PCIE_BUS_PERFORMANCE) {
-                int dev_mpss = 128 << dev->pcie_mpss;
+        /* In the "safe" case, do not configure the MRRS.  There appear to be
+         * issues with setting MRRS to 0 on a number of devices.
+         */
 
-                /* For Max performance, the MRRS must be set to the largest
-                 * supported value.  However, it cannot be configured larger
-                 * than the MPS the device or the bus can support.  This assumes
-                 * that the largest MRRS available on the device cannot be
-                 * smaller than the device MPSS.
-                 */
-                mrrs = mps < dev_mpss ? mps : dev_mpss;
-        } else
-                /* In the "safe" case, configure the MRRS for fairness on the
-                 * bus by making all devices have the same size
-                 */
-                mrrs = mps;
+        if (pcie_bus_config != PCIE_BUS_PERFORMANCE)
+                return;
+
+        dev_mpss = 128 << dev->pcie_mpss;
 
+        /* For Max performance, the MRRS must be set to the largest supported
+         * value.  However, it cannot be configured larger than the MPS the
+         * device or the bus can support.  This assumes that the largest MRRS
+         * available on the device cannot be smaller than the device MPSS.
+         */
+        mrrs = min(mps, dev_mpss);
 
         /* MRRS is a R/W register.  Invalid values can be written, but a
-         * subsiquent read will verify if the value is acceptable or not.
+         * subsequent read will verify if the value is acceptable or not.
          * If the MRRS value provided is not acceptable (e.g., too large),
          * shrink the value until it is acceptable to the HW.
          */
         while (mrrs != pcie_get_readrq(dev) && mrrs >= 128) {
+                dev_warn(&dev->dev, "Attempting to modify the PCI-E MRRS value"
+                         " to %d.  If any issues are encountered, please try "
+                         "running with pci=pcie_bus_safe\n", mrrs);
                 rc = pcie_set_readrq(dev, mrrs);
                 if (rc)
-                        dev_err(&dev->dev, "Failed attempting to set the MRRS\n");
+                        dev_err(&dev->dev,
+                                "Failed attempting to set the MRRS\n");
 
                 mrrs /= 2;
         }
@@ -1436,13 +1439,13 @@ static int pcie_bus_configure_set(struct pci_dev *dev, void *data)
         if (!pci_is_pcie(dev))
                 return 0;
 
-        dev_info(&dev->dev, "Dev MPS %d MPSS %d MRRS %d\n",
+        dev_dbg(&dev->dev, "Dev MPS %d MPSS %d MRRS %d\n",
                  pcie_get_mps(dev), 128<<dev->pcie_mpss, pcie_get_readrq(dev));
 
         pcie_write_mps(dev, mps);
         pcie_write_mrrs(dev, mps);
 
-        dev_info(&dev->dev, "Dev MPS %d MPSS %d MRRS %d\n",
+        dev_dbg(&dev->dev, "Dev MPS %d MPSS %d MRRS %d\n",
                  pcie_get_mps(dev), 128<<dev->pcie_mpss, pcie_get_readrq(dev));
 
         return 0;