linux-kernel - [PATCH] dmaengine: xgene-dma: Disable memcpy operation due to performance drop

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Date:	Thu,  8 Oct 2015 13:55:16 +0530
From:	Rameshwar Prasad Sahu <rsahu@....com>
To:	vinod.koul@...el.com, dan.j.williams@...el.com
Cc:	dmaengine@...r.kernel.org, arnd@...db.de,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, jcm@...hat.com,
	patches@....com, Rameshwar Prasad Sahu <rsahu@....com>
Subject: [PATCH] dmaengine: xgene-dma: Disable memcpy operation due to performance drop

The DMA engine supports memory copy, RAID5 XOR, RAID6 PQ, and other
computations. But the bandwidth of the entire DMA engine is shared
among all channels. This patch re-configures operations availability
such that one can achieve maximum performance for XOR and PQ
computation by removing the memory offload operations.

Signed-off-by: Rameshwar Prasad Sahu <rsahu@....com>
---
 drivers/dma/xgene-dma.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma/xgene-dma.c b/drivers/dma/xgene-dma.c
index 8d57b1b..2998fcb 100644
--- a/drivers/dma/xgene-dma.c
+++ b/drivers/dma/xgene-dma.c
@@ -154,6 +154,7 @@
 #define XGENE_DMA_MAX_XOR_SRC		5
 #define XGENE_DMA_16K_BUFFER_LEN_CODE	0x0
 #define XGENE_DMA_INVALID_LEN_CODE	0x7800000000000000ULL
+#undef XGENE_DMA_MEMCPY_ENABLE

 /* X-Gene DMA descriptor error codes */
 #define ERR_DESC_AXI			0x01
@@ -1707,7 +1708,9 @@ static void xgene_dma_set_caps(struct xgene_dma_chan *chan,
 	dma_cap_zero(dma_dev->cap_mask);

 	/* Set DMA device capability */
+#ifdef XGENE_DMA_MEMCPY_ENABLE
 	dma_cap_set(DMA_MEMCPY, dma_dev->cap_mask);
+#endif
 	dma_cap_set(DMA_SG, dma_dev->cap_mask);

 	/* Basically here, the X-Gene SoC DMA engine channel 0 supports XOR
--
1.8.2.1

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