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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>
This commit is contained in:
Viresh Kumar 2011-08-05 15:32:40 +05:30 committed by Vinod Koul
parent 03af500f74
commit e071916580
1 changed files with 7 additions and 5 deletions
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12
drivers/dma/amba-pl08x.c
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@ -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 "