[PATCH 4/5] dmaengine: edma: Implement device_get_max_len callback

Peter Ujfalusi
2017-09-12T10:45:33Z

﻿eDMA can support maximum of 65535 number of bursts in one transfer.
The limitation is because the CCNT counter is 16bit unsigned.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
---
drivers/dma/edma.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
index 6970355abdc9..14c52574262c 100644
--- a/drivers/dma/edma.c
+++ b/drivers/dma/edma.c
@@ -900,6 +900,28 @@ static int edma_slave_config(struct dma_chan *chan,
return 0;
}

+static u32 edma_get_max_len(struct dma_chan *chan,
+ enum dma_transfer_direction dir)
+{
+ struct edma_chan *echan = to_edma_chan(chan);
+ enum dma_slave_buswidth dev_width;
+ u32 burst;
+
+ if (!is_slave_direction(dir))
+ return 0;
+
+ if (dir == DMA_DEV_TO_MEM) {
+ dev_width = echan->cfg.src_addr_width;
+ burst = echan->cfg.src_maxburst;
+ } else {
+ burst = echan->cfg.dst_maxburst;
+ dev_width = echan->cfg.dst_addr_width;
+ }
+
+ /* CCNT: 16bit unsigned. Number of bursts */
+ return dev_width * burst * (SZ_64K - 1);
+}
+
static int edma_dma_pause(struct dma_chan *chan)
{
struct edma_chan *echan = to_edma_chan(chan);
@@ -1850,6 +1872,7 @@ static void edma_dma_init(struct edma_cc *ecc, bool legacy_mode)
s_ddev->device_issue_pending = edma_issue_pending;
s_ddev->device_tx_status = edma_tx_status;
s_ddev->device_config = edma_slave_config;
+ s_ddev->device_get_max_len = edma_get_max_len;
s_ddev->device_pause = edma_dma_pause;
s_ddev->device_resume = edma_dma_resume;
s_ddev->device_terminate_all = edma_terminate_all;
--
2.14.1