dmaengine: at_xdmac: allow muliple dwidths when doing slave transfers

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@atmel.com>
Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index eba66a22a265..09e2825a547a 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>
@@ -351,11 +352,11 @@ 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 {
@@ -582,7 +583,7 @@ 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);
@@ -613,11 +614,15 @@ 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);