+/**
+ * atc_prep_dma_memset - prepare a memcpy operation
+ * @chan: the channel to prepare operation on
+ * @dest: operation virtual destination address
+ * @value: value to set memory buffer to
+ * @len: operation length
+ * @flags: tx descriptor status flags
+ */
+static struct dma_async_tx_descriptor *
+atc_prep_dma_memset(struct dma_chan *chan, dma_addr_t dest, int value,
+ size_t len, unsigned long flags)
+{
+ struct at_dma_chan *atchan = to_at_dma_chan(chan);
+ struct at_dma *atdma = to_at_dma(chan->device);
+ struct at_desc *desc = NULL;
+ size_t xfer_count;
+ u32 ctrla;
+ u32 ctrlb;
+
+ dev_vdbg(chan2dev(chan), "%s: d0x%x v0x%x l0x%zx f0x%lx\n", __func__,
+ dest, value, len, flags);
+
+ if (unlikely(!len)) {
+ dev_dbg(chan2dev(chan), "%s: length is zero!\n", __func__);
+ return NULL;
+ }
+
+ if (!is_dma_fill_aligned(chan->device, dest, 0, len)) {
+ dev_dbg(chan2dev(chan), "%s: buffer is not aligned\n",
+ __func__);
+ return NULL;
+ }
+
+ xfer_count = len >> 2;
+ if (xfer_count > ATC_BTSIZE_MAX) {
+ dev_err(chan2dev(chan), "%s: buffer is too big\n",
+ __func__);
+ return NULL;
+ }
+
+ ctrlb = ATC_DEFAULT_CTRLB | ATC_IEN
+ | ATC_SRC_ADDR_MODE_FIXED
+ | ATC_DST_ADDR_MODE_INCR
+ | ATC_FC_MEM2MEM;
+
+ ctrla = ATC_SRC_WIDTH(2) |
+ ATC_DST_WIDTH(2);
+
+ desc = atc_desc_get(atchan);
+ if (!desc) {
+ dev_err(chan2dev(chan), "%s: can't get a descriptor\n",
+ __func__);
+ return NULL;
+ }
+
+ desc->memset_vaddr = dma_pool_alloc(atdma->memset_pool, GFP_ATOMIC,
+ &desc->memset_paddr);
+ if (!desc->memset_vaddr) {
+ dev_err(chan2dev(chan), "%s: couldn't allocate buffer\n",
+ __func__);
+ goto err_put_desc;
+ }
+
+ *desc->memset_vaddr = value;
+ desc->memset = true;
+
+ desc->lli.saddr = desc->memset_paddr;
+ desc->lli.daddr = dest;
+ desc->lli.ctrla = ctrla | xfer_count;
+ desc->lli.ctrlb = ctrlb;
+
+ desc->txd.cookie = -EBUSY;
+ desc->len = len;
+ desc->total_len = len;
+
+ /* set end-of-link on the descriptor */
+ set_desc_eol(desc);
+
+ desc->txd.flags = flags;
+
+ return &desc->txd;
+
+err_put_desc:
+ atc_desc_put(atchan, desc);
+ return NULL;
+}
+