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Date: Thu, 4 Mar 2010 14:31:47 +0100
From: Linus Walleij <linus.walleij@...ricsson.com>
To: Dan Williams <dan.j.williams@...el.com>,
linux-kernel@...r.kernel.org
Cc: Linus Walleij <linus.walleij@...ricsson.com>
Subject: [PATCH 1/2] 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@...ricsson.com>
---
drivers/dma/coh901318.c | 103 +++++++++++++++++++++++++++++-----------------
1 files changed, 65 insertions(+), 38 deletions(-)
diff --git a/drivers/dma/coh901318.c b/drivers/dma/coh901318.c
index 1656fdc..20889c9 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);
--
1.6.3.3
--
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