linux-kernel - [PATCH 1/2] dmaengine: Add scatter-gathered memset

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Date:	Mon,  6 Jul 2015 12:19:23 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Vinod Koul <vinod.koul@...el.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	Ludovic Desroches <ludovic.desroches@...el.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: [PATCH 1/2] dmaengine: Add scatter-gathered memset

The current API allows the driver to accelerate memset by using the DMA
controller.

However, it does so over a contiguous memory area, which might proves
inefficient when you have to do it over a non-contiguous yet repititive
pattern, since you have to create a number of descriptors and then submit
each other.

Add a memset operation going over a scatter list to handle such cases in a
single call.

Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
---
 include/linux/dmaengine.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index e2f5eb419976..8da299cc7361 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -66,6 +66,7 @@ enum dma_transaction_type {
 	DMA_XOR_VAL,
 	DMA_PQ_VAL,
 	DMA_MEMSET,
+	DMA_MEMSET_SG,
 	DMA_INTERRUPT,
 	DMA_SG,
 	DMA_PRIVATE,
@@ -616,6 +617,7 @@ struct dma_tx_state {
  * @device_prep_dma_pq: prepares a pq operation
  * @device_prep_dma_pq_val: prepares a pqzero_sum operation
  * @device_prep_dma_memset: prepares a memset operation
+ * @device_prep_dma_memset_sg: prepares a memset operation over a scatter list
  * @device_prep_dma_interrupt: prepares an end of chain interrupt operation
  * @device_prep_slave_sg: prepares a slave dma operation
  * @device_prep_dma_cyclic: prepare a cyclic dma operation suitable for audio.
@@ -682,6 +684,9 @@ struct dma_device {
 	struct dma_async_tx_descriptor *(*device_prep_dma_memset)(
 		struct dma_chan *chan, dma_addr_t dest, int value, size_t len,
 		unsigned long flags);
+	struct dma_async_tx_descriptor *(*device_prep_dma_memset_sg)(
+		struct dma_chan *chan, struct scatterlist *sg,
+		unsigned int nents, int value, unsigned long flags);
 	struct dma_async_tx_descriptor *(*device_prep_dma_interrupt)(
 		struct dma_chan *chan, unsigned long flags);
 	struct dma_async_tx_descriptor *(*device_prep_dma_sg)(
-- 
2.4.5

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