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| author | Viresh Kumar <viresh.kumar@st.com> | 2011-08-05 15:32:38 +0530 |
|---|---|---|
| committer | Vinod Koul <vinod.koul@intel.com> | 2011-08-25 19:33:39 +0530 |
| commit | fa6a940bf129c5417b602a4cdfe88b3dbd8e5898 (patch) | |
| tree | 03355a9b00c59e00cfe157e5a5b7cb06e098bc4b /drivers | |
| parent | 16a2e7d359b9fc64fb8a6717c0642691b1e60bb7 (diff) | |
| download | linux-fa6a940bf129c5417b602a4cdfe88b3dbd8e5898.tar.bz2 | |
dmaengine/amba-pl08x: max_bytes_per_lli is TRANSFER_SIZE * src_width (not MIN(width))
max_bytes_per_lli = bd.srcbus.buswidth * PL080_CONTROL_TRANSFER_SIZE_MASK;
This is confirmed by ARM support guys.
Below is summary of mail exchange with them:
[Viresh] What is the total data to be transferred in case source and destination
bus widths are different. Suppose, source bus width is 2 bytes and destination
is 4 bytes. Now in order to transfer 80 bytes, what should be value of
TransferSize field in control reg: 40? or 20?.
[David from ARM] The value that is programmed into the TransferSize field should
be the number of <SourceWidth> transfers needed to achieve the required data
transfer.
So, to transfer 80 bytes, with a Source Width of 2, the TransferSize field =
should be programmed with:
Total transfer size
------------------- = 40
<source width>
[Viresh] Will this change if source is 4 bytes and dest is 2?
[David] Yes - the calculation then becomes:
Total transfer size
------------------- =20
<source width>
Also, max_bytes_per_lli must be calculated after fixing src and dest widths not
before that. So move this code to the correct place.
This patch also removes max_bytes_per_lli from earlier print message, as till
that point max_bytes_per_lli is unknown.
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')
| -rw-r--r-- | drivers/dma/amba-pl08x.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c index be9a1c718f9a..e5930d512b00 100644 --- a/drivers/dma/amba-pl08x.c +++ b/drivers/dma/amba-pl08x.c @@ -604,23 +604,17 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x, bd.srcbus.buswidth = bd.srcbus.maxwidth; bd.dstbus.buswidth = bd.dstbus.maxwidth; - /* - * Bytes transferred == tsize * MIN(buswidths), not max(buswidths) - */ - max_bytes_per_lli = min(bd.srcbus.buswidth, bd.dstbus.buswidth) * - PL080_CONTROL_TRANSFER_SIZE_MASK; - /* We need to count this down to zero */ bd.remainder = txd->len; pl08x_choose_master_bus(&bd, &mbus, &sbus, cctl); - dev_vdbg(&pl08x->adev->dev, "src=0x%08x%s/%u dst=0x%08x%s/%u len=%zu llimax=%zu\n", + dev_vdbg(&pl08x->adev->dev, "src=0x%08x%s/%u dst=0x%08x%s/%u len=%zu\n", bd.srcbus.addr, cctl & PL080_CONTROL_SRC_INCR ? "+" : "", bd.srcbus.buswidth, bd.dstbus.addr, cctl & PL080_CONTROL_DST_INCR ? "+" : "", bd.dstbus.buswidth, - bd.remainder, max_bytes_per_lli); + bd.remainder); dev_vdbg(&pl08x->adev->dev, "mbus=%s sbus=%s\n", mbus == &bd.srcbus ? "src" : "dst", sbus == &bd.srcbus ? "src" : "dst"); @@ -660,6 +654,10 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x, sbus->buswidth = 1; } + /* Bytes transferred = tsize * src width, not MIN(buswidths) */ + max_bytes_per_lli = bd.srcbus.buswidth * + PL080_CONTROL_TRANSFER_SIZE_MASK; + /* * Make largest possible LLIs until less than one bus * width left |