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Subject[RFC][PATCH 1/3] ARM: OMAP: DMA: Add support for DMA channel self linking on OMAP1510
Date
Implement DMA channel self linking on OMAP1510 using AUTO_INIT and REPEAT
flags of the DMA CCR register.

Created against linux-2.6.31-rc5.

Tested on Amstrad Delta.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>

---
Note:
In its current form, enable_lnk() seems not very consistent (ie. result of a
conditional assignment is then overwritten unconditionally). As rather
different from OMAP1510 that I am familiar with, I am not quite sure how
support for other OMAP models should really look like. So I decided to leave
it as is and put my bit in a separate block, adding an additional FIXME
comment.
--- linux-2.6.31-rc5/arch/arm/plat-omap/dma.c.orig 2009-08-07 13:38:02.000000000 +0200
+++ linux-2.6.31-rc5/arch/arm/plat-omap/dma.c 2009-08-10 09:01:41.000000000 +0200
@@ -653,8 +653,21 @@ static inline void enable_lnk(int lch)
{
u32 l;

+ if (omap_dma_in_1510_mode()) {
+ /* only self linking is supported */
+ if (dma_chan[lch].next_lch == lch) {
+ /* set AUTO_INIT | REPEAT bits in CCR */
+ l = dma_read(CCR(lch));
+ l |= 3 << 8;
+ dma_write(l, CCR(lch));
+ }
+ return;
+ }
+
l = dma_read(CLNK_CTRL(lch));

+ /* FIXME:
+ * this conditional assignment is then overwritten unconditionally */
if (cpu_class_is_omap1())
l &= ~(1 << 14);

@@ -675,13 +688,21 @@ static inline void disable_lnk(int lch)
{
u32 l;

- l = dma_read(CLNK_CTRL(lch));
+ if (omap_dma_in_1510_mode())
+ l = dma_read(CCR(lch));
+ else
+ l = dma_read(CLNK_CTRL(lch));

/* Disable interrupts */
if (cpu_class_is_omap1()) {
dma_write(0, CICR(lch));
- /* Set the STOP_LNK bit */
- l |= 1 << 14;
+ if (omap_dma_in_1510_mode()) {
+ /* Unset AUTO_INIT & REPEAT bits */
+ l &= ~(3 << 8);
+ } else {
+ /* Set the STOP_LNK bit */
+ l |= 1 << 14;
+ }
}

if (cpu_class_is_omap2()) {
@@ -690,7 +711,10 @@ static inline void disable_lnk(int lch)
l &= ~(1 << 15);
}

- dma_write(l, CLNK_CTRL(lch));
+ if (omap_dma_in_1510_mode())
+ dma_write(l, CCR(lch));
+ else
+ dma_write(l, CLNK_CTRL(lch));
dma_chan[lch].flags &= ~OMAP_DMA_ACTIVE;
}

@@ -928,7 +952,7 @@ void omap_start_dma(int lch)
{
u32 l;

- if (!omap_dma_in_1510_mode() && dma_chan[lch].next_lch != -1) {
+ if (dma_chan[lch].next_lch != -1) {
int next_lch, cur_lch;
char dma_chan_link_map[OMAP_DMA4_LOGICAL_DMA_CH_COUNT];

@@ -979,7 +1003,7 @@ void omap_stop_dma(int lch)
{
u32 l;

- if (!omap_dma_in_1510_mode() && dma_chan[lch].next_lch != -1) {
+ if (dma_chan[lch].next_lch != -1) {
int next_lch, cur_lch = lch;
char dma_chan_link_map[OMAP_DMA4_LOGICAL_DMA_CH_COUNT];

@@ -1130,7 +1154,7 @@ int omap_dma_running(void)
*/
void omap_dma_link_lch(int lch_head, int lch_queue)
{
- if (omap_dma_in_1510_mode()) {
+ if (omap_dma_in_1510_mode() && (lch_head != lch_queue)) {
printk(KERN_ERR "DMA linking is not supported in 1510 mode\n");
BUG();
return;
@@ -1152,7 +1176,7 @@ EXPORT_SYMBOL(omap_dma_link_lch);
*/
void omap_dma_unlink_lch(int lch_head, int lch_queue)
{
- if (omap_dma_in_1510_mode()) {
+ if (omap_dma_in_1510_mode() && (lch_head != lch_queue)) {
printk(KERN_ERR "DMA linking is not supported in 1510 mode\n");
BUG();
return;
@@ -1822,7 +1846,7 @@ static int omap1_dma_handle_ch(int ch)
if (unlikely(csr & OMAP_DMA_DROP_IRQ))
printk(KERN_WARNING "DMA synchronization event drop occurred "
"with device %d\n", dma_chan[ch].dev_id);
- if (likely(csr & OMAP_DMA_BLOCK_IRQ))
+ if (likely(csr & OMAP_DMA_BLOCK_IRQ) && (dma_chan[ch].next_lch != ch))
dma_chan[ch].flags &= ~OMAP_DMA_ACTIVE;
if (likely(dma_chan[ch].callback != NULL))
dma_chan[ch].callback(ch, csr, dma_chan[ch].data);

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