+/**
+ * atc_dma_cyclic_check_values
+ * Check for too big/unaligned periods and unaligned DMA buffer
+ */
+static int
+atc_dma_cyclic_check_values(unsigned int reg_width, dma_addr_t buf_addr,
+ size_t period_len, enum dma_data_direction direction)
+{
+ if (period_len > (ATC_BTSIZE_MAX << reg_width))
+ goto err_out;
+ if (unlikely(period_len & ((1 << reg_width) - 1)))
+ goto err_out;
+ if (unlikely(buf_addr & ((1 << reg_width) - 1)))
+ goto err_out;
+ if (unlikely(!(direction & (DMA_TO_DEVICE | DMA_FROM_DEVICE))))
+ goto err_out;
+
+ return 0;
+
+err_out:
+ return -EINVAL;
+}
+
+/**
+ * atc_dma_cyclic_fill_desc - Fill one period decriptor
+ */
+static int
+atc_dma_cyclic_fill_desc(struct at_dma_slave *atslave, struct at_desc *desc,
+ unsigned int period_index, dma_addr_t buf_addr,
+ size_t period_len, enum dma_data_direction direction)
+{
+ u32 ctrla;
+ unsigned int reg_width = atslave->reg_width;
+
+ /* prepare common CRTLA value */
+ ctrla = ATC_DEFAULT_CTRLA | atslave->ctrla
+ | ATC_DST_WIDTH(reg_width)
+ | ATC_SRC_WIDTH(reg_width)
+ | period_len >> reg_width;
+
+ switch (direction) {
+ case DMA_TO_DEVICE:
+ desc->lli.saddr = buf_addr + (period_len * period_index);
+ desc->lli.daddr = atslave->tx_reg;
+ desc->lli.ctrla = ctrla;
+ desc->lli.ctrlb = ATC_DEFAULT_CTRLB
+ | ATC_DST_ADDR_MODE_FIXED
+ | ATC_SRC_ADDR_MODE_INCR
+ | ATC_FC_MEM2PER;
+ break;
+
+ case DMA_FROM_DEVICE:
+ desc->lli.saddr = atslave->rx_reg;
+ desc->lli.daddr = buf_addr + (period_len * period_index);
+ desc->lli.ctrla = ctrla;
+ desc->lli.ctrlb = ATC_DEFAULT_CTRLB
+ | ATC_DST_ADDR_MODE_INCR
+ | ATC_SRC_ADDR_MODE_FIXED
+ | ATC_FC_PER2MEM;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/**
+ * atc_prep_dma_cyclic - prepare the cyclic DMA transfer
+ * @chan: the DMA channel to prepare
+ * @buf_addr: physical DMA address where the buffer starts
+ * @buf_len: total number of bytes for the entire buffer
+ * @period_len: number of bytes for each period
+ * @direction: transfer direction, to or from device
+ */
+static struct dma_async_tx_descriptor *
+atc_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
+ size_t period_len, enum dma_data_direction direction)
+{
+ struct at_dma_chan *atchan = to_at_dma_chan(chan);
+ struct at_dma_slave *atslave = chan->private;
+ struct at_desc *first = NULL;
+ struct at_desc *prev = NULL;
+ unsigned long was_cyclic;
+ unsigned int periods = buf_len / period_len;
+ unsigned int i;
+
+ dev_vdbg(chan2dev(chan), "prep_dma_cyclic: %s buf@0x%08x - %d (%d/%d)\n",
+ direction == DMA_TO_DEVICE ? "TO DEVICE" : "FROM DEVICE",
+ buf_addr,
+ periods, buf_len, period_len);
+
+ if (unlikely(!atslave || !buf_len || !period_len)) {
+ dev_dbg(chan2dev(chan), "prep_dma_cyclic: length is zero!\n");
+ return NULL;
+ }
+
+ was_cyclic = test_and_set_bit(ATC_IS_CYCLIC, &atchan->status);
+ if (was_cyclic) {
+ dev_dbg(chan2dev(chan), "prep_dma_cyclic: channel in use!\n");
+ return NULL;
+ }
+
+ /* Check for too big/unaligned periods and unaligned DMA buffer */
+ if (atc_dma_cyclic_check_values(atslave->reg_width, buf_addr,
+ period_len, direction))
+ goto err_out;
+
+ /* build cyclic linked list */
+ for (i = 0; i < periods; i++) {
+ struct at_desc *desc;
+
+ desc = atc_desc_get(atchan);
+ if (!desc)
+ goto err_desc_get;
+
+ if (atc_dma_cyclic_fill_desc(atslave, desc, i, buf_addr,
+ period_len, direction))
+ goto err_desc_get;
+
+ atc_desc_chain(&first, &prev, desc);
+ }
+
+ /* lets make a cyclic list */
+ prev->lli.dscr = first->txd.phys;
+
+ /* First descriptor of the chain embedds additional information */
+ first->txd.cookie = -EBUSY;
+ first->len = buf_len;
+
+ return &first->txd;
+
+err_desc_get:
+ dev_err(chan2dev(chan), "not enough descriptors available\n");
+ atc_desc_put(atchan, first);
+err_out:
+ clear_bit(ATC_IS_CYCLIC, &atchan->status);
+ return NULL;
+}
+
+