On Mon, Feb 09, 2015 at 05:14:05PM +0900, Yoshihiro Shimoda wrote:
> +struct usb_dmac_chan {
> + struct dma_chan chan;
> + void __iomem *iomem;
> + unsigned int index;
> +
> + spinlock_t lock;
> +
> + struct {
> + struct list_head free;
> + struct list_head pending;
> + struct list_head active;
> + struct list_head done;
> + struct list_head wait;
> + struct usb_dmac_desc *running;
> + struct usb_dmac_desc *last_done;
> +
> + struct list_head chunks_free;
> +
> + struct list_head pages;
Thats too many lists, do we need so many? Shouldn't free and done be same
thing. Similarly whats meant by wait here?
Do you submit multiple descriptors to HW?
> +static dma_cookie_t usb_dmac_tx_submit(struct dma_async_tx_descriptor *tx)
> +{
> + struct usb_dmac_chan *chan = to_usb_dmac_chan(tx->chan);
> + struct usb_dmac_desc *desc = to_usb_dmac_desc(tx);
> + unsigned long flags;
> + dma_cookie_t cookie;
> +
> + spin_lock_irqsave(&chan->lock, flags);
> +
> + cookie = dma_cookie_assign(tx);
> +
> + dev_dbg(chan->chan.device->dev, "chan%u: submit #%d@%p\n",
> + chan->index, tx->cookie, desc);
> +
> + list_add_tail(&desc->node, &chan->desc.pending);
> + desc->running = list_first_entry(&desc->chunks,
> + struct usb_dmac_xfer_chunk, node);
what is this required for?
> +static void usb_dmac_desc_put(struct usb_dmac_chan *chan,
> + struct usb_dmac_desc *desc)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&chan->lock, flags);
> + list_splice_tail_init(&desc->chunks, &chan->desc.chunks_free);
> + list_add_tail(&desc->node, &chan->desc.free);
> + spin_unlock_irqrestore(&chan->lock, flags);
> +}
> +
> +static void usb_dmac_desc_recycle_acked(struct usb_dmac_chan *chan)
what is meant by acked here, and by whom?
> +{
> + struct usb_dmac_desc *desc, *_desc;
> + unsigned long flags;
> + LIST_HEAD(list);
> +
> + /*
> + * We have to temporarily move all descriptors from the wait list to a
> + * local list as iterating over the wait list, even with
> + * list_for_each_entry_safe, isn't safe if we release the channel lock
> + * around the usb_dmac_desc_put() call.
> + */
> + spin_lock_irqsave(&chan->lock, flags);
> + list_splice_init(&chan->desc.wait, &list);
> + spin_unlock_irqrestore(&chan->lock, flags);
> +
> + list_for_each_entry_safe(desc, _desc, &list, node) {
> + if (async_tx_test_ack(&desc->async_tx)) {
Hmmm, this part is not correct. ACK is for async_tx API and not for slave
dmaengine drivers.
> +static int usb_dmac_alloc_chan_resources(struct dma_chan *chan)
> +{
> + struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
> + int ret;
> +
> + INIT_LIST_HEAD(&uchan->desc.chunks_free);
> + INIT_LIST_HEAD(&uchan->desc.pages);
> +
> + /* Preallocate descriptors. */
> + ret = usb_dmac_xfer_chunk_alloc(uchan, GFP_KERNEL);
GFP_NOWAIT
> + if (ret < 0)
> + return -ENOMEM;
> +
> + ret = usb_dmac_desc_alloc(uchan, GFP_KERNEL);
Ditto
> +static int usb_dmac_chan_terminate_all(struct dma_chan *chan)
> +{
> + struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
> + unsigned long flags;
> +
> + spin_lock_irqsave(&uchan->lock, flags);
> + usb_dmac_chan_halt(uchan);
> + spin_unlock_irqrestore(&uchan->lock, flags);
> +
> + /*
> + * FIXME: No new interrupt can occur now, but the IRQ thread might still
> + * be running.
> + */
and when ?
> +static unsigned int
> +usb_dmac_chan_get_residue_if_complete(struct usb_dmac_chan *chan)
> +{
> + struct usb_dmac_desc *desc = chan->desc.last_done;
> + struct usb_dmac_xfer_chunk *chunk = desc ? desc->running : NULL;
> +
> + if (!chunk)
> + return 0;
> +
> + return usb_dmac_chan_get_last_residue(chan, chunk, desc->direction);
and this calls for completed descriptor, wont reading HW be wrong here as
you might have submitted another descriptor?
> +static enum dma_status usb_dmac_tx_status(struct dma_chan *chan,
> + dma_cookie_t cookie,
> + struct dma_tx_state *txstate)
> +{
> + struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
> + enum dma_status status;
> + unsigned long flags;
> + unsigned int residue;
> +
> + status = dma_cookie_status(chan, cookie, txstate);
> + /* a client driver will get residue after DMA_COMPLETE */
> + if (!txstate)
> + return status;
> +
> + spin_lock_irqsave(&uchan->lock, flags);
> + if (status == DMA_COMPLETE)
> + residue = usb_dmac_chan_get_residue_if_complete(uchan);
if it is completed then residue should be zero, so why are we computing this
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int usb_dmac_sleep_suspend(struct device *dev)
> +{
> + /*
> + * TODO: Wait for the current transfer to complete and stop the device.
> + */
> + return 0;
> +}
> +
> +static int usb_dmac_sleep_resume(struct device *dev)
> +{
> + /* TODO: Resume transfers, if any. */
> + return 0;
> +}
> +#endif
what is the point of these?
> +
> +#ifdef CONFIG_PM
> +static int usb_dmac_runtime_suspend(struct device *dev)
> +{
> + return 0;
> +}
ditto
> +static int usb_dmac_chan_probe(struct usb_dmac *dmac,
> + struct usb_dmac_chan *uchan,
> + unsigned int index)
> +{
> + struct platform_device *pdev = to_platform_device(dmac->dev);
> + struct dma_chan *chan = &uchan->chan;
> + char pdev_irqname[5];
> + char *irqname;
> + int irq;
> + int ret;
> +
> + uchan->index = index;
> + uchan->iomem = dmac->iomem + USB_DMAC_CHAN_OFFSET(index);
> +
> + spin_lock_init(&uchan->lock);
> +
> + INIT_LIST_HEAD(&uchan->desc.free);
> + INIT_LIST_HEAD(&uchan->desc.pending);
> + INIT_LIST_HEAD(&uchan->desc.active);
> + INIT_LIST_HEAD(&uchan->desc.done);
> + INIT_LIST_HEAD(&uchan->desc.wait);
> +
> + /* Request the channel interrupt. */
> + sprintf(pdev_irqname, "ch%u", index);
> + irq = platform_get_irq_byname(pdev, pdev_irqname);
> + if (irq < 0) {
> + dev_err(dmac->dev, "no IRQ specified for channel %u\n", index);
> + return -ENODEV;
> + }
> +
> + irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
> + dev_name(dmac->dev), index);
> + if (!irqname)
> + return -ENOMEM;
> +
> + ret = devm_request_threaded_irq(dmac->dev, irq, usb_dmac_isr_channel,
> + usb_dmac_isr_channel_thread,
> + IRQF_SHARED,
> + irqname, uchan);
DMA engine API expects that you are running a tasklet not a thread
> +
> +static int usb_dmac_remove(struct platform_device *pdev)
> +{
> + struct usb_dmac *dmac = platform_get_drvdata(pdev);
> +
> + of_dma_controller_free(pdev->dev.of_node);
> + dma_async_device_unregister(&dmac->engine);
> +
> + pm_runtime_disable(&pdev->dev);
and you have not freed or disabled your irq, neither ensured all
threads/tasklets running are stopped
Overall i feel descriptor management is overtly complicated. Can you see if
you can you use virt-dma infrastructure, that will ease you descriptor management
a lot
Thanks
--
~Vinod
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