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SubjectRe: [PATCH v5] dma: Add Xilinx AXI Direct Memory Access Engine driver support
On Mon, Mar 02, 2015 at 11:25:11PM +0530, Kedareswara rao Appana wrote:
> This is the driver for the AXI Direct Memory Access (AXI DMA)
> core, which is a soft Xilinx IP core that provides high-
> bandwidth direct memory access between memory and AXI4-Stream
> type target peripherals.
>
> Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
> Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
> ---
> This patch is rebased on top of dma: xilinx-dma: move header file
> to common location.
but not on slave-dma next some API update is required..


> +/*
> + * DMA driver for Xilinx DMA Engine
> + *
> + * Copyright (C) 2010 - 2014 Xilinx, Inc. All rights reserved.
2015?

> +static struct xilinx_dma_tx_descriptor *
> +xilinx_dma_alloc_tx_descriptor(struct xilinx_dma_chan *chan)
> +{
> + struct xilinx_dma_tx_descriptor *desc;
> + unsigned long flags;
> +
> + if (chan->allocated_desc)
> + return chan->allocated_desc;
> +
> + desc = kzalloc(sizeof(*desc), GFP_KERNEL);
GFP_NOWAIT

> +static enum dma_status xilinx_dma_tx_status(struct dma_chan *dchan,
> + dma_cookie_t cookie,
> + struct dma_tx_state *txstate)
> +{
> + struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> + enum dma_status ret;
> + unsigned long flags;
> +
> + ret = dma_cookie_status(dchan, cookie, txstate);
> + if (ret != DMA_COMPLETE) {
txstate can be null

> + spin_lock_irqsave(&chan->lock, flags);
> + dma_set_residue(txstate, chan->residue);
the queried descriptor may not be submitted to HW. Also the expectations are
that you will read current value from HW and calculate residue

> +static int xilinx_dma_device_slave_caps(struct dma_chan *dchan,
> + struct dma_slave_caps *caps)
> +{
> + caps->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> + caps->cmd_terminate = true;
> + caps->residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> +
> + return 0;
> +}
this is based on older API, pls update


> +static void xilinx_dma_complete_descriptor(struct xilinx_dma_chan *chan)
> +{
> + struct xilinx_dma_tx_descriptor *desc;
> + struct xilinx_dma_tx_segment *segment, *next;
> + struct xilinx_dma_desc_hw *hw;
> + unsigned long flags;
> + u32 residue = 0;
> +
> + spin_lock_irqsave(&chan->lock, flags);
> +
> + desc = chan->active_desc;
> + if (!desc) {
> + dev_dbg(chan->dev, "no running descriptors\n");
> + goto out_unlock;
> + }
> +
> + if (chan->has_sg) {
> + list_for_each_entry_safe(segment, next, &desc->segments, node) {
> + hw = &segment->hw;
> + residue += (hw->control - hw->status) &
> + XILINX_DMA_MAX_TRANS_LEN;
> + }
why are we calculating residue here?
> + }
> +
> + chan->residue = residue;
and this is used in status call, so completely wrong!

> +static dma_cookie_t xilinx_dma_tx_submit(struct dma_async_tx_descriptor *tx)
> +{
> + struct xilinx_dma_tx_descriptor *desc = to_dma_tx_descriptor(tx);
> + struct xilinx_dma_chan *chan = to_xilinx_chan(tx->chan);
> + dma_cookie_t cookie;
> + unsigned long flags;
> + int err;
> +
> + if (chan->err) {
> + /*
> + * If reset fails, need to hard reset the system.
> + * Channel is no longer functional
> + */
> + err = xilinx_dma_reset(chan);
> + if (err < 0)
> + return err;
> + }
> +
> + spin_lock_irqsave(&chan->lock, flags);
> +
> + cookie = dma_cookie_assign(tx);
> +
> + /* Append the transaction to the pending transactions queue. */
> + list_add_tail(&desc->node, &chan->pending_list);
> +
> + /* Free the allocated desc */
> + chan->allocated_desc = NULL;
this bit is confusing, can you explain what is going on?

> +static struct dma_async_tx_descriptor *xilinx_dma_prep_slave_sg(
> + struct dma_chan *dchan, struct scatterlist *sgl, unsigned int sg_len,
> + enum dma_transfer_direction direction, unsigned long flags,
> + void *context)
> +{
> + struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> + struct xilinx_dma_tx_descriptor *desc;
> + struct xilinx_dma_tx_segment *segment;
> + struct xilinx_dma_desc_hw *hw;
> + u32 *app_w = (u32 *)context;
> + struct scatterlist *sg;
> + size_t copy, sg_used;
> + int i;
> +
> + if (!is_slave_direction(direction))
> + return NULL;
> +
> + /* Allocate a transaction descriptor. */
> + desc = xilinx_dma_alloc_tx_descriptor(chan);
> + if (!desc)
> + return NULL;
> +
> + desc->direction = direction;
> + dma_async_tx_descriptor_init(&desc->async_tx, &chan->common);
> + desc->async_tx.tx_submit = xilinx_dma_tx_submit;
> + desc->async_tx.cookie = 0;
?

> + async_tx_ack(&desc->async_tx);
why?

> +
> + /* Build transactions using information in the scatter gather list */
> + for_each_sg(sgl, sg, sg_len, i) {
> + sg_used = 0;
> +
> + /* Loop until the entire scatterlist entry is used */
> + while (sg_used < sg_dma_len(sg)) {
> +
> + /* Get a free segment */
> + segment = xilinx_dma_alloc_tx_segment(chan);
> + if (!segment)
> + goto error;
> +
> + /*
> + * Calculate the maximum number of bytes to transfer,
> + * making sure it is less than the hw limit
> + */
> + copy = min_t(size_t, sg_dma_len(sg) - sg_used,
> + XILINX_DMA_MAX_TRANS_LEN);
> + hw = &segment->hw;
> +
> + /* Fill in the descriptor */
> + hw->buf_addr = sg_dma_address(sg) + sg_used;
> +
> + hw->control = copy;
> +
> + if (direction == DMA_MEM_TO_DEV) {
> + if (app_w)
> + memcpy(hw->app, app_w, sizeof(u32) *
> + XILINX_DMA_NUM_APP_WORDS);
> +
> + /*
> + * For the first DMA_MEM_TO_DEV transfer,
> + * set SOP
> + */
> + if (!i)
> + hw->control |= XILINX_DMA_BD_SOP;
> + }
no else?

> +static int xilinx_dma_remove(struct platform_device *pdev)
> +{
> + struct xilinx_dma_device *xdev = platform_get_drvdata(pdev);
> + int i;
> +
> + of_dma_controller_free(pdev->dev.of_node);
> + dma_async_device_unregister(&xdev->common);
> +
> + for (i = 0; i < XILINX_DMA_MAX_CHANS_PER_DEVICE; i++)
> + if (xdev->chan[i])
> + xilinx_dma_chan_remove(xdev->chan[i]);
> +
at this point your irq is active and tasklet cna still be scheduled


--
~Vinod


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