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authorDan Williams <dan.j.williams@intel.com>2009-01-06 13:38:14 -0500
committerDan Williams <dan.j.williams@intel.com>2009-01-06 13:38:14 -0500
commit6f49a57aa5a0c6d4e4e27c85f7af6c83325a12d1 (patch)
treeafba24357d1f4ff69ccb2b39a19542546590a50b /drivers/mmc
parent07f2211e4fbce6990722d78c4f04225da9c0e9cf (diff)
dmaengine: up-level reference counting to the module level
Simply, if a client wants any dmaengine channel then prevent all dmaengine modules from being removed. Once the clients are done re-enable module removal. Why?, beyond reducing complication: 1/ Tracking reference counts per-transaction in an efficient manner, as is currently done, requires a complicated scheme to avoid cache-line bouncing effects. 2/ Per-transaction ref-counting gives the false impression that a dma-driver can be gracefully removed ahead of its user (net, md, or dma-slave) 3/ None of the in-tree dma-drivers talk to hot pluggable hardware, but if such an engine were built one day we still would not need to notify clients of remove events. The driver can simply return NULL to a ->prep() request, something that is much easier for a client to handle. Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/mmc')
-rw-r--r--drivers/mmc/host/atmel-mci.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index 7a3f2436b011..6c11f4d4c4e9 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -593,10 +593,8 @@ atmci_submit_data_dma(struct atmel_mci *host, struct mmc_data *data)
593 593
594 /* If we don't have a channel, we can't do DMA */ 594 /* If we don't have a channel, we can't do DMA */
595 chan = host->dma.chan; 595 chan = host->dma.chan;
596 if (chan) { 596 if (chan)
597 dma_chan_get(chan);
598 host->data_chan = chan; 597 host->data_chan = chan;
599 }
600 598
601 if (!chan) 599 if (!chan)
602 return -ENODEV; 600 return -ENODEV;