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Message-ID: <5521ee74eef41cf26a9f1ece6dadd32cca529cce.1311936524.git.viresh.kumar@st.com>
Date: Fri, 29 Jul 2011 16:19:21 +0530
From: Viresh Kumar <viresh.kumar@...com>
To: <linus.walleij@...aro.org>
Cc: <vinod.koul@...el.com>, <dan.j.williams@...el.com>,
<linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <linux@....linux.org.uk>,
<armando.visconti@...com>, <shiraz.hashim@...com>,
<vipin.kumar@...com>, <rajeev-dlh.kumar@...com>,
<deepak.sikri@...com>, <vipulkumar.samar@...com>,
<amit.virdi@...com>, <viresh.kumar@...com>,
<pratyush.anand@...com>, <bhupesh.sharma@...com>,
<viresh.linux@...il.com>
Subject: [PATCH 11/18] 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@...com>
---
drivers/dma/amba-pl08x.c | 15 ++++++---------
1 files changed, 6 insertions(+), 9 deletions(-)
diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
index 04f7889..3b7357e 100644
--- a/drivers/dma/amba-pl08x.c
+++ b/drivers/dma/amba-pl08x.c
@@ -597,24 +597,17 @@ 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");
@@ -654,6 +647,10 @@ 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
--
1.7.2.2
--
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