DMA: AT91: Get residual bytes in dma buffer

Add support for returning the residue for current transfer cookie by
reading the transfered buffer size(BTSIZE) in CTRLA register.

For a single buffer cookie, the descriptor length minus BTSIZE
can get the residue.

For a lli cookie, remain_desc will record remain descriptor length
when last descriptor finish, the remain_desc minus BTSIZE can get the
current residue.

If the cookie has completed successfully, the residue will be zero.
If the cookie is in progress, it will be the number of bytes yet to be transferred.
If get residue error, the cookie will be turn into error status.

Check dma fifo to see if data remain, let issue pending finish remain work if there is.
Signed-off-by: Elen Song <elen.song@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/dma/at_hdmac_regs.h b/drivers/dma/at_hdmac_regs.h
index 3679933fb646..f31d647acdfa 100644
--- a/drivers/dma/at_hdmac_regs.h
+++ b/drivers/dma/at_hdmac_regs.h
@@ -213,6 +213,7 @@ txd_to_at_desc(struct dma_async_tx_descriptor *txd)
 enum atc_status {
 	ATC_IS_ERROR = 0,
 	ATC_IS_PAUSED = 1,
+	ATC_IS_BTC = 2,
 	ATC_IS_CYCLIC = 24,
 };
 
@@ -230,6 +231,7 @@ enum atc_status {
  * @save_cfg: configuration register that is saved on suspend/resume cycle
  * @save_dscr: for cyclic operations, preserve next descriptor address in
  *             the cyclic list on suspend/resume cycle
+ * @remain_desc: to save remain desc length
  * @dma_sconfig: configuration for slave transfers, passed via DMA_SLAVE_CONFIG
  * @lock: serializes enqueue/dequeue operations to descriptors lists
  * @active_list: list of descriptors dmaengine is being running on
@@ -248,6 +250,7 @@ struct at_dma_chan {
 	struct tasklet_struct	tasklet;
 	u32			save_cfg;
 	u32			save_dscr;
+	u32			remain_desc;
 	struct dma_slave_config dma_sconfig;
 
 	spinlock_t		lock;