[Bug 15014] Poor performance on O2 Micro carbus bridge (OZ6933)

[bugzilla-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=15014





--- Comment #2 from Wolfram Sang <w.sang at pengutronix.de>  2010-01-09 16:29:18 ---
O2-bridges can do read prefetch and write burst. However, for some combinations
of older bridges and cards, this causes problems, so it is disabled for those
bridges. Now, as some users know their setup works with the speedups enabled, a
new parameter is introduced to the driver. Now, a user can specifically enable
or disable these features, while the default is what we have today: detect the
bridge and decide accordingly.

Simplify and unify the printouts while we are here.

Signed-off-by: Wolfram Sang <w.sang at pengutronix.de>
Cc: frodone at gmail.com
Cc: Dominik Brodowski <linux at dominikbrodowski.net>
---

frodone: Can you please test this patch? It is just compile-tested as I don't
have access to the hardware I'd need this weekend.

 drivers/pcmcia/o2micro.h      |   38 +++++++++++++++++++++++++-------------
 drivers/pcmcia/yenta_socket.c |    5 +++++
 2 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/drivers/pcmcia/o2micro.h b/drivers/pcmcia/o2micro.h
index 624442f..d98cc01 100644
--- a/drivers/pcmcia/o2micro.h
+++ b/drivers/pcmcia/o2micro.h
@@ -116,13 +116,12 @@ static int o2micro_override(struct yenta_socket *socket)
      * from Eric Still, 02Micro.
      */
     u8 a, b;
+    bool use_speedup;

     if (PCI_FUNC(socket->dev->devfn) == 0) {
         a = config_readb(socket, O2_RESERVED1);
         b = config_readb(socket, O2_RESERVED2);
-
-        dev_printk(KERN_INFO, &socket->dev->dev,
-               "O2: res at 0x94/0xD4: %02x/%02x\n", a, b);
+        dev_dbg(&socket->dev->dev, "O2: 0x94/0xD4: %02x/%02x\n", a, b);

         switch (socket->dev->device) {
         /*
@@ -136,22 +135,35 @@ static int o2micro_override(struct yenta_socket *socket)
         case PCI_DEVICE_ID_O2_6832:
         case PCI_DEVICE_ID_O2_6836:
          case PCI_DEVICE_ID_O2_6933:
-            dev_printk(KERN_INFO, &socket->dev->dev,
-                   "Yenta O2: old bridge, disabling read "
-                   "prefetch/write burst\n");
-            config_writeb(socket, O2_RESERVED1,
-                          a & ~(O2_RES_READ_PREFETCH | O2_RES_WRITE_BURST));
-            config_writeb(socket, O2_RESERVED2,
-                          b & ~(O2_RES_READ_PREFETCH | O2_RES_WRITE_BURST));
+            use_speedup = false;
             break;
-
         default:
-            dev_printk(KERN_INFO , &socket->dev->dev,
-                   "O2: enabling read prefetch/write burst\n");
+            use_speedup = true;
+            break;
+        }
+
+        if (strcasecmp(o2_speedup, "on") == 0)
+            use_speedup = true;
+        else if (strcasecmp(o2_speedup, "off") == 0)
+            use_speedup = false;
+        else if (strcasecmp(o2_speedup, "default") != 0)
+            dev_warn(&socket->dev->dev,
+                "O2: Unknown parameter, using 'default'");
+
+        if (use_speedup) {
+            dev_info(&socket->dev->dev,
+                "O2: enabling read prefetch/write burst\n");
             config_writeb(socket, O2_RESERVED1,
                           a | O2_RES_READ_PREFETCH | O2_RES_WRITE_BURST);
             config_writeb(socket, O2_RESERVED2,
                           b | O2_RES_READ_PREFETCH | O2_RES_WRITE_BURST);
+        } else {
+            dev_info(&socket->dev->dev,
+                "O2: disabling read prefetch/write burst\n");
+            config_writeb(socket, O2_RESERVED1,
+                          a & ~(O2_RES_READ_PREFETCH | O2_RES_WRITE_BURST));
+            config_writeb(socket, O2_RESERVED2,
+                          b & ~(O2_RES_READ_PREFETCH | O2_RES_WRITE_BURST));
         }
     }

diff --git a/drivers/pcmcia/yenta_socket.c b/drivers/pcmcia/yenta_socket.c
index e4d12ac..041a75a 100644
--- a/drivers/pcmcia/yenta_socket.c
+++ b/drivers/pcmcia/yenta_socket.c
@@ -37,6 +37,11 @@ static int pwr_irqs_off;
 module_param(pwr_irqs_off, bool, 0644);
 MODULE_PARM_DESC(pwr_irqs_off, "Force IRQs off during power-on of slot. Use
only when seeing IRQ storms!");

+static char o2_speedup[] = "default";
+module_param_string(o2_speedup, o2_speedup, sizeof(o2_speedup), 0444);
+MODULE_PARM_DESC(o2_speedup, "Use prefetch/burst for O2-bridges: 'on', 'off' "
+    "or 'default' (uses recommended behaviour for the detected bridge)");
+
 #define debug(x, s, args...) dev_dbg(&s->dev->dev, x, ##args)

 /* Don't ask.. */

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