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iop_adma: document how to calculate the minimum descriptor pool size

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Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2008-07-17 17:59:56 -07:00
parent c7141d005a
commit 5eb907aaaf
1 changed files with 10 additions and 1 deletions
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11
drivers/dma/iop-adma.c
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@ -450,7 +450,16 @@ iop_adma_tx_submit(struct dma_async_tx_descriptor *tx)
static void iop_chan_start_null_memcpy(struct iop_adma_chan *iop_chan); static void iop_chan_start_null_memcpy(struct iop_adma_chan *iop_chan);
static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan); static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan);
/* returns the number of allocated descriptors */ /**
* iop_adma_alloc_chan_resources - returns the number of allocated descriptors
* @chan - allocate descriptor resources for this channel
* @client - current client requesting the channel be ready for requests
*
* Note: We keep the slots for 1 operation on iop_chan->chain at all times. To
* avoid deadlock, via async_xor, num_descs_in_pool must at a minimum be
* greater than 2x the number slots needed to satisfy a device->max_xor
* request.
* */
static int iop_adma_alloc_chan_resources(struct dma_chan *chan, static int iop_adma_alloc_chan_resources(struct dma_chan *chan,
struct dma_client *client) struct dma_client *client)
{ {