ieee1394: support for slow links or slow 1394b phy ports

Add support for the following types of hardware:
 + nodes that have a link speed < PHY speed
 + 1394b PHYs that are less than S800 capable
 + 1394b/1394a adapter cable between two 1394b PHYs
Also, S1600 and S3200 are now supported if IEEE1394_SPEED_MAX is raised.

A probing function is added to nodemgr's config ROM fetching routine
which adjusts the allowable speed if an access problem was encountered.
Pros and Cons of the approach:
 + minimum code footprint to support this less widely used hardware
 + nearly no overhead for unaffected hardware
 - ineffective before nodemgr began to read the ROM of affected nodes
 - ineffective if ieee1394 is loaded with disable_nodemgr=1
The speed map CSRs which are published to the bus are not touched by the
patch.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Hakan Ardo <hakan@debian.org>
Cc: Calculex <linux@calculex.com>
Cc: Robert J. Kosinski <robk@cmcherald.com>
Signed-off-by: Ben Collins <bcollins@ubuntu.com>

1 files changed, 58 insertions, 3 deletions

diff --git a/drivers/ieee1394/nodemgr.c b/drivers/ieee1394/nodemgr.c
index 082c7fd239f5..948f1b8c4238 100644
--- a/drivers/ieee1394/nodemgr.c
+++ b/drivers/ieee1394/nodemgr.c
@@ -38,6 +38,7 @@ struct nodemgr_csr_info {
         struct hpsb_host *host;
         nodeid_t nodeid;
         unsigned int generation;
+        unsigned int speed_unverified:1;
 };
 
 
@@ -57,23 +58,75 @@ static char *nodemgr_find_oui_name(int oui)
         return NULL;
 }
 
+/*
+ * Correct the speed map entry.  This is necessary
+ *  - for nodes with link speed < phy speed,
+ *  - for 1394b nodes with negotiated phy port speed < IEEE1394_SPEED_MAX.
+ * A possible speed is determined by trial and error, using quadlet reads.
+ */
+static int nodemgr_check_speed(struct nodemgr_csr_info *ci, u64 addr,
+                               quadlet_t *buffer)
+{
+        quadlet_t q;
+        u8 i, *speed, old_speed, good_speed;
+        int ret;
+
+        speed = ci->host->speed + NODEID_TO_NODE(ci->nodeid);
+        old_speed = *speed;
+        good_speed = IEEE1394_SPEED_MAX + 1;
+
+        /* Try every speed from S100 to old_speed.
+         * If we did it the other way around, a too low speed could be caught
+         * if the retry succeeded for some other reason, e.g. because the link
+         * just finished its initialization. */
+        for (i = IEEE1394_SPEED_100; i <= old_speed; i++) {
+                *speed = i;
+                ret = hpsb_read(ci->host, ci->nodeid, ci->generation, addr,
+                                &q, sizeof(quadlet_t));
+                if (ret)
+                        break;
+                *buffer = q;
+                good_speed = i;
+        }
+        if (good_speed <= IEEE1394_SPEED_MAX) {
+                HPSB_DEBUG("Speed probe of node " NODE_BUS_FMT " yields %s",
+                           NODE_BUS_ARGS(ci->host, ci->nodeid),
+                           hpsb_speedto_str[good_speed]);
+                *speed = good_speed;
+                ci->speed_unverified = 0;
+                return 0;
+        }
+        *speed = old_speed;
+        return ret;
+}
 
 static int nodemgr_bus_read(struct csr1212_csr *csr, u64 addr, u16 length,
                             void *buffer, void *__ci)
 {
         struct nodemgr_csr_info *ci = (struct nodemgr_csr_info*)__ci;
-        int i, ret = 0;
+        int i, ret;
 
         for (i = 1; ; i++) {
                 ret = hpsb_read(ci->host, ci->nodeid, ci->generation, addr,
                                 buffer, length);
-                if (!ret || i == 3)
+                if (!ret) {
+                        ci->speed_unverified = 0;
+                        break;
+                }
+                /* Give up after 3rd failure. */
+                if (i == 3)
                         break;
 
+                /* The ieee1394_core guessed the node's speed capability from
+                 * the self ID.  Check whether a lower speed works. */
+                if (ci->speed_unverified && length == sizeof(quadlet_t)) {
+                        ret = nodemgr_check_speed(ci, addr, buffer);
+                        if (!ret)
+                                break;
+                }
                 if (msleep_interruptible(334))
                         return -EINTR;
         }
-
         return ret;
 }
 
@@ -1204,6 +1257,8 @@ static void nodemgr_node_scan_one(struct host_info *hi,
         ci->host = host;
         ci->nodeid = nodeid;
         ci->generation = generation;
+        ci->speed_unverified =
+                host->speed[NODEID_TO_NODE(nodeid)] > IEEE1394_SPEED_100;
 
         /* We need to detect when the ConfigROM's generation has changed,
          * so we only update the node's info when it needs to be.  */