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authorDan Williams <dan.j.williams@intel.com>2008-07-17 20:59:56 -0400
committerDan Williams <dan.j.williams@intel.com>2008-07-17 20:59:56 -0400
commit5eb907aaaf7a316a0097ff9f8c21bf9fc468a1f1 (patch)
tree33238b492dc0f823e59586ca2a2ec981c3ba9f74
parentc7141d005a19d2a0a316b3bf9c170d3bedf07bfd (diff)
iop_adma: document how to calculate the minimum descriptor pool size
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
-rw-r--r--drivers/dma/iop-adma.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/dma/iop-adma.c b/drivers/dma/iop-adma.c
index 8acbc3ab0b92..85bfeba4d85e 100644
--- a/drivers/dma/iop-adma.c
+++ b/drivers/dma/iop-adma.c
@@ -450,7 +450,16 @@ iop_adma_tx_submit(struct dma_async_tx_descriptor *tx)
450static void iop_chan_start_null_memcpy(struct iop_adma_chan *iop_chan); 450static void iop_chan_start_null_memcpy(struct iop_adma_chan *iop_chan);
451static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan); 451static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan);
452 452
453/* returns the number of allocated descriptors */ 453/**
454 * iop_adma_alloc_chan_resources - returns the number of allocated descriptors
455 * @chan - allocate descriptor resources for this channel
456 * @client - current client requesting the channel be ready for requests
457 *
458 * Note: We keep the slots for 1 operation on iop_chan->chain at all times. To
459 * avoid deadlock, via async_xor, num_descs_in_pool must at a minimum be
460 * greater than 2x the number slots needed to satisfy a device->max_xor
461 * request.
462 * */
454static int iop_adma_alloc_chan_resources(struct dma_chan *chan, 463static int iop_adma_alloc_chan_resources(struct dma_chan *chan,
455 struct dma_client *client) 464 struct dma_client *client)
456{ 465{