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SubjectRe: [PATCH v2 1/5] dmaengine: add ep93xx DMA support
Hello.

During adaptation of my experimental ep93xx ide driver to the new dmaengine api,
I discovered two issues with ep93xx dma implementation:
1) Control register is incorrectly programmed for IDE (m2m_hw_setup),
probably copy-paste bug ;)
2) Kernel oops when trying to stop running transfers by calling
dmaengine_terminate_all(...) - caused by dereferencing empty list
in ep93xx_dma_get_active

Following is a patch, which solves these problems for me.

Regards,
Rafal Prylowski

Index: linux-2.6/drivers/dma/ep93xx_dma.c
===================================================================
--- linux-2.6.orig/drivers/dma/ep93xx_dma.c
+++ linux-2.6/drivers/dma/ep93xx_dma.c
@@ -246,6 +246,7 @@ static void ep93xx_dma_set_active(struct
static struct ep93xx_dma_desc *
ep93xx_dma_get_active(struct ep93xx_dma_chan *edmac)
{
+ BUG_ON(list_empty(&edmac->active));
return list_first_entry(&edmac->active, struct ep93xx_dma_desc, node);
}

@@ -459,9 +460,6 @@ static int m2m_hw_setup(struct ep93xx_dm
* This IDE part is totally untested. Values below are taken
* from the EP93xx Users's Guide and might not be correct.
*/
- control |= M2M_CONTROL_NO_HDSK;
- control |= M2M_CONTROL_RSS_IDE;
- control |= M2M_CONTROL_PW_16;

if (data->direction == DMA_TO_DEVICE) {
/* Worst case from the UG */
@@ -473,6 +471,9 @@ static int m2m_hw_setup(struct ep93xx_dm
control |= M2M_CONTROL_SAH;
control |= M2M_CONTROL_TM_RX;
}
+ control |= M2M_CONTROL_NO_HDSK;
+ control |= M2M_CONTROL_RSS_IDE;
+ control |= M2M_CONTROL_PW_16;
break;

default:
@@ -668,24 +669,28 @@ static void ep93xx_dma_unmap_buffers(str
static void ep93xx_dma_tasklet(unsigned long data)
{
struct ep93xx_dma_chan *edmac = (struct ep93xx_dma_chan *)data;
- struct ep93xx_dma_desc *desc, *d;
- dma_async_tx_callback callback;
- void *callback_param;
+ struct ep93xx_dma_desc *desc = NULL, *d;
+ dma_async_tx_callback callback = NULL;
+ void *callback_param = NULL;
LIST_HEAD(list);

spin_lock_irq(&edmac->lock);
- desc = ep93xx_dma_get_active(edmac);
- if (desc->complete) {
- edmac->last_completed = desc->txd.cookie;
- list_splice_init(&edmac->active, &list);
+ if (!list_empty(&edmac->active)) {
+ desc = ep93xx_dma_get_active(edmac);
+ if (desc->complete) {
+ edmac->last_completed = desc->txd.cookie;
+ list_splice_init(&edmac->active, &list);
+ }
}
spin_unlock_irq(&edmac->lock);

/* Pick up the next descriptor from the queue */
ep93xx_dma_advance_work(edmac);

- callback = desc->txd.callback;
- callback_param = desc->txd.callback_param;
+ if (desc) {
+ callback = desc->txd.callback;
+ callback_param = desc->txd.callback_param;
+ }

/* Now we can release all the chained descriptors */
list_for_each_entry_safe(desc, d, &list, node) {

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