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>

diff --git a/drivers/dma/coh901318.c b/drivers/dma/coh901318.c
index 1656fdcdb6c244cd8ed73b8d212790f8ebde8c5c..20889c98e9b0af4e34ba76d87481185231daf41a 100644 (file)
--- 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);