DMAENGINE: COH 901 318 rename confusing vars

This fixes up the code with a lot of comments that make it readable,
rename things with opaque names like "data" into something more
appropriate, and remove some very confusing BUG() statements.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 65 insertions, 38 deletions

diff --git a/drivers/dma/coh901318.c b/drivers/dma/coh901318.c
index 1656fdcdb6c2..20889c98e9b0 100644
--- a/drivers/dma/coh901318.c
+++ b/drivers/dma/coh901318.c
@@ -37,7 +37,7 @@ struct coh901318_desc {
         struct list_head node;
         struct scatterlist *sg;
         unsigned int sg_len;
-        struct coh901318_lli *data;
+        struct coh901318_lli *lli;
         enum dma_data_direction dir;
         unsigned long flags;
 };
@@ -283,7 +283,7 @@ static int coh901318_start(struct coh901318_chan *cohc)
 }
 
 static int coh901318_prep_linked_list(struct coh901318_chan *cohc,
-                                      struct coh901318_lli *data)
+                                      struct coh901318_lli *lli)
 {
         int channel = cohc->id;
         void __iomem *virtbase = cohc->base->virtbase;
@@ -292,18 +292,18 @@ static int coh901318_prep_linked_list(struct coh901318_chan *cohc,
                      COH901318_CX_STAT_SPACING*channel) &
                COH901318_CX_STAT_ACTIVE);
 
-        writel(data->src_addr,
+        writel(lli->src_addr,
                virtbase + COH901318_CX_SRC_ADDR +
                COH901318_CX_SRC_ADDR_SPACING * channel);
 
-        writel(data->dst_addr, virtbase +
+        writel(lli->dst_addr, virtbase +
                COH901318_CX_DST_ADDR +
                COH901318_CX_DST_ADDR_SPACING * channel);
 
-        writel(data->link_addr, virtbase + COH901318_CX_LNK_ADDR +
+        writel(lli->link_addr, virtbase + COH901318_CX_LNK_ADDR +
                COH901318_CX_LNK_ADDR_SPACING * channel);
 
-        writel(data->control, virtbase + COH901318_CX_CTRL +
+        writel(lli->control, virtbase + COH901318_CX_CTRL +
                COH901318_CX_CTRL_SPACING * channel);
 
         return 0;
@@ -565,29 +565,30 @@ static int coh901318_config(struct coh901318_chan *cohc,
  */
 static struct coh901318_desc *coh901318_queue_start(struct coh901318_chan *cohc)
 {
-        struct coh901318_desc *cohd_que;
+        struct coh901318_desc *cohd;
 
-        /* start queued jobs, if any
+        /*
+         * start queued jobs, if any
          * TODO: transmit all queued jobs in one go
          */
-        cohd_que = coh901318_first_queued(cohc);
+        cohd = coh901318_first_queued(cohc);
 
-        if (cohd_que != NULL) {
+        if (cohd != NULL) {
                 /* Remove from queue */
-                coh901318_desc_remove(cohd_que);
+                coh901318_desc_remove(cohd);
                 /* initiate DMA job */
                 cohc->busy = 1;
 
-                coh901318_desc_submit(cohc, cohd_que);
+                coh901318_desc_submit(cohc, cohd);
 
-                coh901318_prep_linked_list(cohc, cohd_que->data);
+                coh901318_prep_linked_list(cohc, cohd->lli);
 
-                /* start dma job */
+                /* start dma job on this channel */
                 coh901318_start(cohc);
 
         }
 
-        return cohd_que;
+        return cohd;
 }
 
 /*
@@ -622,7 +623,7 @@ static void dma_tasklet(unsigned long data)
         cohc->completed = cohd_fin->desc.cookie;
 
         /* release the lli allocation and remove the descriptor */
-        coh901318_lli_free(&cohc->base->pool, &cohd_fin->data);
+        coh901318_lli_free(&cohc->base->pool, &cohd_fin->lli);
 
         /* return desc to free-list */
         coh901318_desc_remove(cohd_fin);
@@ -666,23 +667,44 @@ static void dma_tasklet(unsigned long data)
 /* called from interrupt context */
 static void dma_tc_handle(struct coh901318_chan *cohc)
 {
-        BUG_ON(!cohc->allocated && (list_empty(&cohc->active) ||
-                                    list_empty(&cohc->queue)));
-
-        if (!cohc->allocated)
+        /*
+         * If the channel is not allocated, then we shouldn't have
+         * any TC interrupts on it.
+         */
+        if (!cohc->allocated) {
+                dev_err(COHC_2_DEV(cohc), "spurious interrupt from "
+                        "unallocated channel\n");
                 return;
+        }
 
         spin_lock(&cohc->lock);
 
+        /*
+         * When we reach this point, at least one queue item
+         * should have been moved over from cohc->queue to
+         * cohc->active and run to completion, that is why we're
+         * getting a terminal count interrupt is it not?
+         * If you get this BUG() the most probable cause is that
+         * the individual nodes in the lli chain have IRQ enabled,
+         * so check your platform config for lli chain ctrl.
+         */
+        BUG_ON(list_empty(&cohc->active));
+
         cohc->nbr_active_done++;
 
+        /*
+         * This attempt to take a job from cohc->queue, put it
+         * into cohc->active and start it.
+         */
         if (coh901318_queue_start(cohc) == NULL)
                 cohc->busy = 0;
 
-        BUG_ON(list_empty(&cohc->active));
-
         spin_unlock(&cohc->lock);
 
+        /*
+         * This tasklet will remove items from cohc->active
+         * and thus terminates them.
+         */
         if (cohc_chan_conf(cohc)->priority_high)
                 tasklet_hi_schedule(&cohc->tasklet);
         else
@@ -870,7 +892,7 @@ static struct dma_async_tx_descriptor *
 coh901318_prep_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
                       size_t size, unsigned long flags)
 {
-        struct coh901318_lli *data;
+        struct coh901318_lli *lli;
         struct coh901318_desc *cohd;
         unsigned long flg;
         struct coh901318_chan *cohc = to_coh901318_chan(chan);
@@ -892,23 +914,23 @@ coh901318_prep_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
         if ((lli_len << MAX_DMA_PACKET_SIZE_SHIFT) < size)
                 lli_len++;
 
-        data = coh901318_lli_alloc(&cohc->base->pool, lli_len);
+        lli = coh901318_lli_alloc(&cohc->base->pool, lli_len);
 
-        if (data == NULL)
+        if (lli == NULL)
                 goto err;
 
         ret = coh901318_lli_fill_memcpy(
-                &cohc->base->pool, data, src, size, dest,
+                &cohc->base->pool, lli, src, size, dest,
                 cohc_chan_param(cohc)->ctrl_lli_chained,
                 ctrl_last);
         if (ret)
                 goto err;
 
-        COH_DBG(coh901318_list_print(cohc, data));
+        COH_DBG(coh901318_list_print(cohc, lli));
 
         /* Pick a descriptor to handle this transfer */
         cohd = coh901318_desc_get(cohc);
-        cohd->data = data;
+        cohd->lli = lli;
         cohd->flags = flags;
         cohd->desc.tx_submit = coh901318_tx_submit;
 
@@ -926,7 +948,7 @@ coh901318_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
                         unsigned long flags)
 {
         struct coh901318_chan *cohc = to_coh901318_chan(chan);
-        struct coh901318_lli *data;
+        struct coh901318_lli *lli;
         struct coh901318_desc *cohd;
         const struct coh901318_params *params;
         struct scatterlist *sg;
@@ -999,13 +1021,13 @@ coh901318_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
         }
 
         pr_debug("Allocate %d lli:s for this transfer\n", len);
-        data = coh901318_lli_alloc(&cohc->base->pool, len);
+        lli = coh901318_lli_alloc(&cohc->base->pool, len);
 
-        if (data == NULL)
+        if (lli == NULL)
                 goto err_dma_alloc;
 
-        /* initiate allocated data list */
-        ret = coh901318_lli_fill_sg(&cohc->base->pool, data, sgl, sg_len,
+        /* initiate allocated lli list */
+        ret = coh901318_lli_fill_sg(&cohc->base->pool, lli, sgl, sg_len,
                                     cohc_dev_addr(cohc),
                                     ctrl_chained,
                                     ctrl,
@@ -1014,14 +1036,14 @@ coh901318_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
         if (ret)
                 goto err_lli_fill;
 
-        COH_DBG(coh901318_list_print(cohc, data));
+        COH_DBG(coh901318_list_print(cohc, lli));
 
         /* Pick a descriptor to handle this transfer */
         cohd = coh901318_desc_get(cohc);
         cohd->dir = direction;
         cohd->flags = flags;
         cohd->desc.tx_submit = coh901318_tx_submit;
-        cohd->data = data;
+        cohd->lli = lli;
 
         spin_unlock_irqrestore(&cohc->lock, flg);
 
@@ -1065,7 +1087,12 @@ coh901318_issue_pending(struct dma_chan *chan)
 
         spin_lock_irqsave(&cohc->lock, flags);
 
-        /* Busy means that pending jobs are already being processed */
+        /*
+         * Busy means that pending jobs are already being processed,
+         * and then there is no point in starting the queue: the
+         * terminal count interrupt on the channel will take the next
+         * job on the queue and execute it anyway.
+         */
         if (!cohc->busy)
                 coh901318_queue_start(cohc);
 
@@ -1099,7 +1126,7 @@ coh901318_terminate_all(struct dma_chan *chan)
 
         while ((cohd = coh901318_first_active_get(cohc))) {
                 /* release the lli allocation*/
-                coh901318_lli_free(&cohc->base->pool, &cohd->data);
+                coh901318_lli_free(&cohc->base->pool, &cohd->lli);
 
                 /* return desc to free-list */
                 coh901318_desc_remove(cohd);
@@ -1108,7 +1135,7 @@ coh901318_terminate_all(struct dma_chan *chan)
 
         while ((cohd = coh901318_first_queued(cohc))) {
                 /* release the lli allocation*/
-                coh901318_lli_free(&cohc->base->pool, &cohd->data);
+                coh901318_lli_free(&cohc->base->pool, &cohd->lli);
 
                 /* return desc to free-list */
                 coh901318_desc_remove(cohd);