[PATCH 5/5] dmaengine: omap-dma: Implement device_get_max_len callback

Peter Ujfalusi
2017-09-12T10:45:04Z

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

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

diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
index f6dd849159d8..6418be98a782 100644
--- a/drivers/dma/omap-dma.c
+++ b/drivers/dma/omap-dma.c
@@ -1297,6 +1297,28 @@ static int omap_dma_slave_config(struct dma_chan *chan, struct dma_slave_config
return 0;
}

+static u32 omap_dma_get_max_len(struct dma_chan *chan,
+ enum dma_transfer_direction dir)
+{
+ struct omap_chan *c = to_omap_dma_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 = c->cfg.src_addr_width;
+ burst = c->cfg.src_maxburst;
+ } else {
+ burst = c->cfg.dst_maxburst;
+ dev_width = c->cfg.dst_addr_width;
+ }
+
+ /* CFN: 16bit unsigned. Number of bursts */
+ return dev_width * burst * (SZ_64K - 1);
+}
+
static int omap_dma_terminate_all(struct dma_chan *chan)
{
struct omap_chan *c = to_omap_dma_chan(chan);
@@ -1478,6 +1500,7 @@ static int omap_dma_probe(struct platform_device *pdev)
od->ddev.device_prep_dma_memcpy = omap_dma_prep_dma_memcpy;
od->ddev.device_prep_interleaved_dma = omap_dma_prep_dma_interleaved;
od->ddev.device_config = omap_dma_slave_config;
+ od->ddev.device_get_max_len = omap_dma_get_max_len;
od->ddev.device_pause = omap_dma_pause;
od->ddev.device_resume = omap_dma_resume;
od->ddev.device_terminate_all = omap_dma_terminate_all;
--
2.14.1