When using FIFO, we need to support differents data width in a single
transfer. For example, serial device which usually uses 1-byte data
width will use 4-bytes data width when using the FIFO. If the transfer
size is not aligned on 4-bytes then the end of the transfer will be
performed with 1-byte data-width. For that reason,
at_xdmac_prep_slave_sg() now builds linked list descriptors using view 2
instead of view 1 so each of them can update the DWIDTH field into the
Channel Configuration Register.
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx>
Signed-off-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
---
drivers/dma/at_xdmac.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 94b714e..64f5b7f 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -25,6 +25,7 @@
#include <linux/dmapool.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
+#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of_dma.h>
@@ -352,11 +353,11 @@ static void at_xdmac_start_xfer(struct at_xdmac_chan *atchan,
at_xdmac_chan_write(atchan, AT_XDMAC_CNDA, reg);
/*
- * When doing memory to memory transfer we need to use the next
+ * When doing non cyclic transfer we need to use the next
* descriptor view 2 since some fields of the configuration register
* depend on transfer size and src/dest addresses.
*/
- if (is_slave_direction(first->direction)) {
+ if (at_xdmac_chan_is_cyclic(atchan)) {
reg = AT_XDMAC_CNDC_NDVIEW_NDV1;
at_xdmac_chan_write(atchan, AT_XDMAC_CC, first->lld.mbr_cfg);
} else {
@@ -583,7 +584,7 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
/* Prepare descriptors. */
for_each_sg(sgl, sg, sg_len, i) {
struct at_xdmac_desc *desc = NULL;
- u32 len, mem;
+ u32 len, mem, dwidth, fixed_dwidth;
len = sg_dma_len(sg);
mem = sg_dma_address(sg);
@@ -614,11 +615,15 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
desc->lld.mbr_da = atchan->per_dst_addr;
desc->lld.mbr_cfg = atchan->cfg[AT_XDMAC_MEM_TO_DEV_CFG];
}
- desc->lld.mbr_ubc = AT_XDMAC_MBR_UBC_NDV1 /* next descriptor view */
+ dwidth = at_xdmac_get_dwidth(desc->lld.mbr_cfg);
+ fixed_dwidth = IS_ALIGNED(len, 1 << dwidth)
+ ? at_xdmac_get_dwidth(desc->lld.mbr_cfg)
+ : AT_XDMAC_CC_DWIDTH_BYTE;
+ desc->lld.mbr_ubc = AT_XDMAC_MBR_UBC_NDV2 /* next descriptor view */
| AT_XDMAC_MBR_UBC_NDEN /* next descriptor dst parameter update */
| AT_XDMAC_MBR_UBC_NSEN /* next descriptor src parameter update */
| (i == sg_len - 1 ? 0 : AT_XDMAC_MBR_UBC_NDE) /* descriptor fetch */
- | len / (1 << at_xdmac_get_dwidth(desc->lld.mbr_cfg)); /* microblock length */
+ | (len >> fixed_dwidth); /* microblock length */
dev_dbg(chan2dev(chan),
"%s: lld: mbr_sa=%pad, mbr_da=%pad, mbr_ubc=0x%08x\n",
__func__, &desc->lld.mbr_sa, &desc->lld.mbr_da, desc->lld.mbr_ubc);
--
2.0.3
--
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