From: Ludovic Desroches <ludovic.desroc...@atmel.com>
For most devices the FIFO configuration is the same i.e. when half FIFO size is
available/filled, a source/destination request is serviced. But USART devices
have to do it when there is enough space/data available to perform a single
AHB access so the ASAP configuration.
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagn...@jcrosoft.com>
Signed-off-by: Ludovic Desroches <ludovic.desroc...@atmel.com>
---
.../devicetree/bindings/dma/atmel-dma.txt | 7 ++++--
drivers/dma/at_hdmac.c | 25 ++++++++++++++++++----
2 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/Documentation/devicetree/bindings/dma/atmel-dma.txt
b/Documentation/devicetree/bindings/dma/atmel-dma.txt
index c80e8a3..c280a0e 100644
--- a/Documentation/devicetree/bindings/dma/atmel-dma.txt
+++ b/Documentation/devicetree/bindings/dma/atmel-dma.txt
@@ -24,8 +24,11 @@ The three cells in order are:
1. A phandle pointing to the DMA controller.
2. The memory interface (16 most significant bits), the peripheral interface
(16 less significant bits).
-3. The peripheral identifier for the hardware handshaking interface. The
-identifier can be different for tx and rx.
+3. Parameters for the at91 DMA configuration register which are device
+dependant:
+ - bit 7-0: peripheral identifier for the hardware handshaking interface. The
+ identifier can be different for tx and rx.
+ - bit 11-8: FIFO configuration. 0 for half FIFO, 1 for ALAP, 1 for ASAP.
Example:
diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index e923cda..bfd73e1 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -14,6 +14,7 @@
* found on AT91SAM9263.
*/
+#include <dt-bindings/dma/at91.h>
#include <linux/clk.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
@@ -1223,14 +1224,30 @@ static struct dma_chan *at_dma_xlate(struct
of_phandle_args *dma_spec,
atslave = devm_kzalloc(&dmac_pdev->dev, sizeof(*atslave), GFP_KERNEL);
if (!atslave)
return NULL;
+
+ atslave->cfg = ATC_DST_H2SEL_HW | ATC_SRC_H2SEL_HW;
/*
* We can fill both SRC_PER and DST_PER, one of these fields will be
* ignored depending on DMA transfer direction.
*/
- per_id = dma_spec->args[1];
- atslave->cfg = ATC_FIFOCFG_HALFFIFO | ATC_DST_H2SEL_HW
- | ATC_SRC_H2SEL_HW | ATC_DST_PER(per_id)
- | ATC_SRC_PER(per_id);
+ per_id = dma_spec->args[1] & AT91_DMA_CFG_PER_ID_MASK;
+ atslave->cfg |= ATC_DST_PER(per_id) | ATC_SRC_PER(per_id);
+ /*
+ * We have to translate the value we get from the device tree since
+ * the half FIFO configuration value had to be 0 to keep backward
+ * compatibility.
+ */
+ switch(dma_spec->args[1] & AT91_DMA_CFG_FIFOCFG_MASK) {
+ case AT91_DMA_CFG_FIFOCFG_ALAP:
+ atslave->cfg |= ATC_FIFOCFG_LARGESTBURST;
+ break;
+ case AT91_DMA_CFG_FIFOCFG_ASAP:
+ atslave->cfg |= ATC_FIFOCFG_ENOUGHSPACE;
+ break;
+ case AT91_DMA_CFG_FIFOCFG_HALF:
+ default:
+ atslave->cfg |= ATC_FIFOCFG_HALFFIFO;
+ }
atslave->dma_dev = &dmac_pdev->dev;
chan = dma_request_channel(mask, at_dma_filter, atslave);
--
1.7.11.3
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