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| author | Dan Williams <dan.j.williams@intel.com> | 2008-07-17 17:59:56 -0700 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2008-07-17 17:59:56 -0700 |
| commit | 5eb907aaaf7a316a0097ff9f8c21bf9fc468a1f1 (patch) | |
| tree | 33238b492dc0f823e59586ca2a2ec981c3ba9f74 /drivers/dma/iop-adma.c | |
| parent | c7141d005a19d2a0a316b3bf9c170d3bedf07bfd (diff) | |
| download | lwn-5eb907aaaf7a316a0097ff9f8c21bf9fc468a1f1.tar.gz lwn-5eb907aaaf7a316a0097ff9f8c21bf9fc468a1f1.zip | |
iop_adma: document how to calculate the minimum descriptor pool size
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/dma/iop-adma.c')
| -rw-r--r-- | drivers/dma/iop-adma.c | 11 |
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) 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); -/* 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, struct dma_client *client) { |