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| author |   Viresh Kumar <viresh.kumar@st.com> | 2011-08-05 15:32:40 +0530 |
|---|---|---|
| committer |   Vinod Koul <vinod.koul@intel.com> | 2011-08-25 19:33:39 +0530 |
| commit | e0719165801fad04073e7dcd90e4afd02aba3fb7 (patch) | |
| tree | 8b1cb65f26487d6fa0aba776e88c8e9b7f0aa22c /drivers/dma | |
| parent | dmaengine/amba-pl08x: Add prep_single_byte_llis() routine (diff) | |
| download | linux-dev-e0719165801fad04073e7dcd90e4afd02aba3fb7.tar.xz linux-dev-e0719165801fad04073e7dcd90e4afd02aba3fb7.zip | |
dmaengine/amba-pl08x: Align lli_len to max(src.width, dst.width)
Currently lli_len is aligned to min of two widths, which looks to be incorrect.
Instead it should be aligned to max of both widths.
Lets say, total_size = 441 bytes
MIN: lets check if min() suits or not:
CASE 1: srcwidth = 1, dstwidth = 4
min(src, dst) = 1
i.e. We program transfer size in control reg to 441.
Now, till 440 bytes everything is fine, but on the last byte DMAC can't transfer
1 byte to dst, as its width is 4.
CASE 2: srcwidth = 4, dstwidth = 1
min(src, dst) = 1
i.e. we program transfer size in control reg to 110 (data transferred = 110 * srcwidth).
So, here too 1 byte is left, but on the source side.
MAX: Lets check if max() suits or not:
CASE 3: srcwidth = 1, dstwidth = 4
max(src, dst) = 4
Aligned size is 440
i.e. We program transfer size in control reg to 440.
Now, all 440 bytes will be transferred without any issues.
CASE 4: srcwidth = 4, dstwidth = 1
max(src, dst) = 4
Aligned size is 440
i.e. We program transfer size in control reg to 110 (data transferred = 110 * srcwidth).
Now, also all 440 bytes will be transferred without any issues.
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'drivers/dma')
| -rw-r--r-- | drivers/dma/amba-pl08x.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c index 45d8a5d5bccd..4bcf6036f35d 100644 --- a/drivers/dma/amba-pl08x.c +++ b/drivers/dma/amba-pl08x.c @@ -669,20 +669,22 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x, * width left */ while (bd.remainder > (mbus->buswidth - 1)) { - size_t lli_len, tsize; + size_t lli_len, tsize, width; /* * If enough left try to send max possible, * otherwise try to send the remainder */ lli_len = min(bd.remainder, max_bytes_per_lli); + /* - * Check against minimum bus alignment: Calculate actual + * Check against maximum bus alignment: Calculate actual * transfer size in relation to bus width and get a - * maximum remainder of the smallest bus width - 1 + * maximum remainder of the highest bus width - 1 */ - tsize = lli_len / min(mbus->buswidth, sbus->buswidth); - lli_len = tsize * min(mbus->buswidth, sbus->buswidth); + width = max(mbus->buswidth, sbus->buswidth); + lli_len = (lli_len / width) * width; + tsize = lli_len / bd.srcbus.buswidth; dev_vdbg(&pl08x->adev->dev, "%s fill lli with single lli chunk of " |