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Message-Id: <1285370032-16937-2-git-send-email-iws@ovro.caltech.edu>
Date: Fri, 24 Sep 2010 16:13:51 -0700
From: "Ira W. Snyder" <iws@...o.caltech.edu>
To: linux-kernel@...r.kernel.org
Cc: Dan Williams <dan.j.williams@...el.com>,
linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH RFCv2 1/2] dmaengine: add support for scatterlist to scatterlist transfers
This adds support for scatterlist to scatterlist DMA transfers. This is
currently hidden behind a configuration option, which will allow drivers
which need this functionality to select it individually.
Signed-off-by: Ira W. Snyder <iws@...o.caltech.edu>
---
drivers/dma/Kconfig | 3 +
drivers/dma/dmaengine.c | 125 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/dmaengine.h | 6 ++
3 files changed, 134 insertions(+), 0 deletions(-)
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 9520cf0..82d2244 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -89,6 +89,9 @@ config AT_HDMAC
Support the Atmel AHB DMA controller. This can be integrated in
chips such as the Atmel AT91SAM9RL.
+config DMAENGINE_SG_TO_SG
+ bool
+
config FSL_DMA
tristate "Freescale Elo and Elo Plus DMA support"
depends on FSL_SOC
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 9d31d5e..9238b86 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -972,6 +972,131 @@ dma_async_memcpy_pg_to_pg(struct dma_chan *chan, struct page *dest_pg,
}
EXPORT_SYMBOL(dma_async_memcpy_pg_to_pg);
+#ifdef CONFIG_DMAENGINE_SG_TO_SG
+dma_cookie_t
+dma_async_memcpy_sg_to_sg(struct dma_chan *chan,
+ struct scatterlist *dst_sg, unsigned int dst_nents,
+ struct scatterlist *src_sg, unsigned int src_nents,
+ dma_async_tx_callback cb, void *cb_param)
+{
+ struct dma_device *dev = chan->device;
+ struct dma_async_tx_descriptor *tx;
+ dma_cookie_t cookie = -ENOMEM;
+ size_t dst_avail, src_avail;
+ struct scatterlist *sg;
+ size_t transferred = 0;
+ size_t dst_total = 0;
+ size_t src_total = 0;
+ dma_addr_t dst, src;
+ size_t len;
+ int i;
+
+ if (dst_nents == 0 || src_nents == 0)
+ return -EINVAL;
+
+ if (dst_sg == NULL || src_sg == NULL)
+ return -EINVAL;
+
+ /* get the total count of bytes in each scatterlist */
+ for_each_sg(dst_sg, sg, dst_nents, i)
+ dst_total += sg_dma_len(sg);
+
+ for_each_sg(src_sg, sg, src_nents, i)
+ src_total += sg_dma_len(sg);
+
+ /* get prepared for the loop */
+ dst_avail = sg_dma_len(dst_sg);
+ src_avail = sg_dma_len(src_sg);
+
+ /* run until we are out of descriptors */
+ while (true) {
+
+ /* create the largest transaction possible */
+ len = min_t(size_t, src_avail, dst_avail);
+ if (len == 0)
+ goto fetch;
+
+ dst = sg_dma_address(dst_sg) + sg_dma_len(dst_sg) - dst_avail;
+ src = sg_dma_address(src_sg) + sg_dma_len(src_sg) - src_avail;
+
+ /*
+ * get a descriptor
+ *
+ * we must poll for a descriptor here since the DMAEngine API
+ * does not provide a way for external users to free previously
+ * allocated descriptors
+ */
+ for (;;) {
+ tx = dev->device_prep_dma_memcpy(chan, dst, src, len, 0);
+ if (likely(tx))
+ break;
+
+ dma_async_issue_pending(chan);
+ }
+
+ /* update metadata */
+ transferred += len;
+ dst_avail -= len;
+ src_avail -= len;
+
+ /* if this is the last transfer, setup the callback */
+ if (dst_total == transferred || src_total == transferred) {
+ tx->callback = cb;
+ tx->callback_param = cb_param;
+ }
+
+ /* submit the transaction */
+ cookie = tx->tx_submit(tx);
+ if (dma_submit_error(cookie)) {
+ dev_err(dev->dev, "failed to submit desc\n");
+ return cookie;
+ }
+
+fetch:
+ /* fetch the next dst scatterlist entry */
+ if (dst_avail == 0) {
+
+ /* no more entries: we're done */
+ if (dst_nents == 0)
+ break;
+
+ /* fetch the next entry: if there are no more: done */
+ dst_sg = sg_next(dst_sg);
+ if (dst_sg == NULL)
+ break;
+
+ dst_nents--;
+ dst_avail = sg_dma_len(dst_sg);
+ }
+
+ /* fetch the next src scatterlist entry */
+ if (src_avail == 0) {
+
+ /* no more entries: we're done */
+ if (src_nents == 0)
+ break;
+
+ /* fetch the next entry: if there are no more: done */
+ src_sg = sg_next(src_sg);
+ if (src_sg == NULL)
+ break;
+
+ src_nents--;
+ src_avail = sg_dma_len(src_sg);
+ }
+ }
+
+ /* update counters */
+ preempt_disable();
+ __this_cpu_add(chan->local->bytes_transferred, transferred);
+ __this_cpu_inc(chan->local->memcpy_count);
+ preempt_enable();
+
+ return 0;
+}
+EXPORT_SYMBOL(dma_async_memcpy_sg_to_sg);
+#endif
+
void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
struct dma_chan *chan)
{
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index c61d4ca..28803a0 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -632,6 +632,12 @@ dma_cookie_t dma_async_memcpy_buf_to_pg(struct dma_chan *chan,
dma_cookie_t dma_async_memcpy_pg_to_pg(struct dma_chan *chan,
struct page *dest_pg, unsigned int dest_off, struct page *src_pg,
unsigned int src_off, size_t len);
+#ifdef CONFIG_DMAENGINE_SG_TO_SG
+dma_cookie_t dma_async_memcpy_sg_to_sg(struct dma_chan *chan,
+ struct scatterlist *dst_sg, unsigned int dst_nents,
+ struct scatterlist *src_sg, unsigned int src_nents,
+ dma_async_tx_callback cb, void *cb_param);
+#endif
void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
struct dma_chan *chan);
--
1.7.1
--
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