1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/ieee1394/ohci1394.c b/drivers/ieee1394/ohci1394.c
index 0690469fcecf..e509e13cb7a7 100644
--- a/drivers/ieee1394/ohci1394.c
+++ b/drivers/ieee1394/ohci1394.c
@@ -1723,6 +1723,8 @@ struct ohci_iso_xmit {
         struct dma_prog_region prog;
         struct ohci1394_iso_tasklet task;
         int task_active;
+        int last_cycle;
+        atomic_t skips;
 
         u32 ContextControlSet;
         u32 ContextControlClear;
@@ -1759,6 +1761,8 @@ static int ohci_iso_xmit_init(struct hpsb_iso *iso)
         iso->hostdata = xmit;
         xmit->ohci = iso->host->hostdata;
         xmit->task_active = 0;
+        xmit->last_cycle = -1;
+        atomic_set(&iso->skips, 0);
 
         dma_prog_region_init(&xmit->prog);
 
@@ -1856,6 +1860,26 @@ static void ohci_iso_xmit_task(unsigned long data)
                 /* parse cycle */
                 cycle = le32_to_cpu(cmd->output_last.status) & 0x1FFF;
 
+                if (xmit->last_cycle > -1) {
+                        int cycle_diff = cycle - xmit->last_cycle;
+                        int skip;
+
+                        /* unwrap */
+                        if (cycle_diff < 0) {
+                                cycle_diff += 8000;
+                                if (cycle_diff < 0)
+                                        PRINT(KERN_ERR, "bogus cycle diff %d\n",
+                                              cycle_diff);
+                        }
+
+                        skip = cycle_diff - 1;
+                        if (skip > 0) {
+                                DBGMSG("skipped %d cycles without packet loss", skip);
+                                atomic_add(skip, &iso->skips);
+                        }
+                }
+                xmit->last_cycle = cycle;
+
                 /* tell the subsystem the packet has gone out */
                 hpsb_iso_packet_sent(iso, cycle, event != 0x11);
 
@@ -1943,6 +1967,16 @@ static int ohci_iso_xmit_queue(struct hpsb_iso *iso, struct hpsb_iso_packet_info
         prev->output_last.branchAddress = cpu_to_le32(
                 dma_prog_region_offset_to_bus(&xmit->prog, sizeof(struct iso_xmit_cmd) * next_i) | 3);
 
+        /*
+         * Link the skip address to this descriptor itself. This causes a
+         * context to skip a cycle whenever lost cycles or FIFO overruns occur,
+         * without dropping the data at that point the application should then
+         * decide whether this is an error condition or not. Some protocols
+         * can deal with this by dropping some rate-matching padding packets.
+         */
+        next->output_more_immediate.branchAddress =
+                        prev->output_last.branchAddress;
+
         /* disable interrupt, unless required by the IRQ interval */
         if (prev_i % iso->irq_interval) {
                 prev->output_last.control &= cpu_to_le32(~(3 << 20)); /* no interrupt */