[2/4] dmaengine: imx-sdma - update the residue calculation for cyclic channels
diff mbox series

Message ID 0e47cf5eb88ef63f844f310bfbd836264f65ccdf.1470656658.git.nandor.han@ge.com
State New, archived
Headers show
Series
  • serial,dmaengine: use DMA cyclic for IMX UART driver
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Commit Message

Nandor Han Aug. 8, 2016, 12:38 p.m. UTC
The calculation of the DMA transaction residue supports only fixed
size data transfers. This implementation is not covering all
operations (e.g. data receiving) when we need to know the exact amount
of bytes transferred.

The loop channels handling was changed to clear the buffer
descriptor errors and use the bd->mode.count to calculate the
residue.

Tested-by: Peter Senna Tschudin <peter.senna@collabora.com>
Acked-by: Peter Senna Tschudin <peter.senna@collabora.com>
Reviewed-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Nandor Han <nandor.han@ge.com>
---
 drivers/dma/imx-sdma.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

Patch
diff mbox series

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index aa35a77..3cb4738 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -651,6 +651,8 @@  static void sdma_event_disable(struct sdma_channel *sdmac, unsigned int event)
 static void sdma_update_channel_loop(struct sdma_channel *sdmac)
 {
 	struct sdma_buffer_descriptor *bd;
+	int error = 0;
+	enum dma_status	old_status = sdmac->status;
 
 	/*
 	 * loop mode. Iterate over descriptors, re-setup them and
@@ -662,10 +664,20 @@  static void sdma_update_channel_loop(struct sdma_channel *sdmac)
 		if (bd->mode.status & BD_DONE)
 			break;
 
-		if (bd->mode.status & BD_RROR)
+		if (bd->mode.status & BD_RROR) {
+			bd->mode.status &= ~BD_RROR;
 			sdmac->status = DMA_ERROR;
+			error = -EIO;
+		}
 
+	       /*
+		* We use bd->mode.count to calculate the residue, since contains
+		* the number of bytes present in the current buffer descriptor.
+		*/
+
+		sdmac->chn_real_count = bd->mode.count;
 		bd->mode.status |= BD_DONE;
+		bd->mode.count = sdmac->period_len;
 
 		/*
 		 * The callback is called from the interrupt context in order
@@ -679,6 +691,9 @@  static void sdma_update_channel_loop(struct sdma_channel *sdmac)
 
 		sdmac->buf_tail++;
 		sdmac->buf_tail %= sdmac->num_bd;
+
+		if (error)
+			sdmac->status = old_status;
 	}
 }
 
@@ -1349,7 +1364,8 @@  static enum dma_status sdma_tx_status(struct dma_chan *chan,
 	u32 residue;
 
 	if (sdmac->flags & IMX_DMA_SG_LOOP)
-		residue = (sdmac->num_bd - sdmac->buf_tail) * sdmac->period_len;
+		residue = (sdmac->num_bd - sdmac->buf_tail) *
+			   sdmac->period_len - sdmac->chn_real_count;
 	else
 		residue = sdmac->chn_count - sdmac->chn_real_count;