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dma: Add dma_bytes_done() to return bytes completed in a dma channel

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By subtracting the current dma count from the number of bytes originally
requested to be transferred, we can find out how many bytes have been
transferred so far.

BUG=chrome-os-partner:10533
TEST=build and boot on snow

Change-Id: Ideee1ed27c08b56882f5d2095341fe04bbe9c34b
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/26167
Reviewed-by: David Hendricks <dhendrix@chromium.org>
This commit is contained in:
Simon Glass
2012-06-26 16:12:29 -07:00
committed by Gerrit
parent 1c0f99d13f
commit 79353032e0
2 changed files with 20 additions and 0 deletions
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7
chip/stm32/dma.c
View File

@@ -97,6 +97,13 @@ int dma_start_rx(unsigned channel, unsigned count, void *periph,
return 0;
}
int dma_bytes_done(struct dma_channel *chan, int orig_count)
{
if (!(REG32(&chan->ccr) & DMA_EN))
return 0;
return orig_count - REG32(&chan->cndtr);
}
/* Hide this code behind an undefined CONFIG for now */
#ifdef CONFIG_DMA_TEST

13
chip/stm32/dma.h
View File

@@ -117,6 +117,19 @@ int dma_start_rx(unsigned channel, unsigned count, void *periph,
*/
void dma_disable(unsigned channel);
/**
* Get the number of bytes available to read, or number of bytes written
*
* Since the DMA controller counts downwards, if we know the starting value
* we can work out how many bytes have been completed so far.
*
* @param chan DMA channel to check (use dma_get_channel())
* @param orig_count Original number of bytes requested on channel
* @return number of bytes completed on a channel, or 0 if this channel is
* not enabled
*/
int dma_bytes_done(struct dma_channel *chan, int orig_count);
/**
* Start a previously-prepared dma channel
*