+/*
+ * Handle DEAD DMA transfers:
+ * if the TX status comes up "DEAD" - reported on some Power Computing machines
+ * we need to re-start the dbdma - but from a different physical start address
+ * and with a different transfer length. It would get very messy to do this
+ * with the normal dbdma_cmd blocks - we would have to re-write the buffer start
+ * addresses each time. So, we will keep a single dbdma_cmd block which can be
+ * fiddled with.
+ * When DEAD status is first reported the content of the faulted dbdma block is
+ * copied into the emergency buffer and we note that the buffer is in use.
+ * we then bump the start physical address by the amount that was successfully
+ * output before it died.
+ * On any subsequent DEAD result we just do the bump-ups (we know that we are
+ * already using the emergency dbdma_cmd).
+ * CHECK: this just tries to "do it". It is possible that we should abandon
+ * xfers when the number of residual bytes gets below a certain value - I can
+ * see that this might cause a loop-forever if a too small transfer causes
+ * DEAD status. However this is a TODO for now - we'll see what gets reported.
+ * When we get a successful transfer result with the emergency buffer we just
+ * pretend that it completed using the original dmdma_cmd and carry on. The
+ * 'next_cmd' field will already point back to the original loop of blocks.
+ */
+static inline void snd_pmac_pcm_dead_xfer(struct pmac_stream *rec,
+ volatile struct dbdma_cmd __iomem *cp)
+{
+ unsigned short req, res ;
+ unsigned int phy ;
+
+ /* printk(KERN_WARNING "snd-powermac: DMA died - patching it up!\n"); */
+
+ /* to clear DEAD status we must first clear RUN
+ set it to quiescent to be on the safe side */
+ (void)in_le32(&rec->dma->status);
+ out_le32(&rec->dma->control, (RUN|PAUSE|FLUSH|WAKE) << 16);
+
+ if (!emergency_in_use) { /* new problem */
+ memcpy((void *)emergency_dbdma.cmds, (void *)cp,
+ sizeof(struct dbdma_cmd));
+ emergency_in_use = 1;
+ st_le16(&cp->xfer_status, 0);
+ st_le16(&cp->req_count, rec->period_size);
+ cp = emergency_dbdma.cmds;
+ }
+
+ /* now bump the values to reflect the amount
+ we haven't yet shifted */
+ req = ld_le16(&cp->req_count);
+ res = ld_le16(&cp->res_count);
+ phy = ld_le32(&cp->phy_addr);
+ phy += (req - res);
+ st_le16(&cp->req_count, res);
+ st_le16(&cp->res_count, 0);
+ st_le16(&cp->xfer_status, 0);
+ st_le32(&cp->phy_addr, phy);
+
+ st_le32(&cp->cmd_dep, rec->cmd.addr
+ + sizeof(struct dbdma_cmd)*((rec->cur_period+1)%rec->nperiods));
+
+ st_le16(&cp->command, OUTPUT_MORE | BR_ALWAYS | INTR_ALWAYS);
+
+ /* point at our patched up command block */
+ out_le32(&rec->dma->cmdptr, emergency_dbdma.addr);
+
+ /* we must re-start the controller */
+ (void)in_le32(&rec->dma->status);
+ /* should complete clearing the DEAD status */
+ out_le32(&rec->dma->control, ((RUN|WAKE) << 16) + (RUN|WAKE));
+}
+