linux-kernel - [PATCH v3 3/3] dmaengine: imx-sdma: allocate max 20 bds for one transfer

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Date:   Tue, 24 Jul 2018 01:46:12 +0800
From:   Robin Gong <yibin.gong@....com>
To:     vkoul@...nel.org, dan.j.williams@...el.com, s.hauer@...gutronix.de,
        linux@...linux.org.uk
Cc:     linux-arm-kernel@...ts.infradead.org, kernel@...gutronix.de,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-imx@....com
Subject: [PATCH v3 3/3] dmaengine: imx-sdma: allocate max 20 bds for one transfer

If multi-bds used in one transfer, all bds should be consisten
memory.To easily follow it, enlarge the dma pool size into 20 bds,
and it will report error if the number of bds is over than 20. For
dmatest, the max count for single transfer is NUM_BD *
SDMA_BD_MAX_CNT = 20 * 65535 = ~1.28MB.

Signed-off-by: Robin Gong <yibin.gong@....com>
---
 drivers/dma/imx-sdma.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index b4ec2d2..5973489 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -298,6 +298,15 @@ struct sdma_context_data {
 	u32  scratch7;
 } __attribute__ ((packed));
 
+/*
+ * All bds in one transfer should be consitent on SDMA. To easily follow it,just
+ * set the dma pool size as the enough bds. For example, in dmatest case, the
+ * max 20 bds means the max for single transfer is NUM_BD * SDMA_BD_MAX_CNT = 20
+ * * 65535 = ~1.28MB. 20 bds supposed to be enough basically.If it's still not
+ * enough in some specific cases, enlarge it here.Warning message would also
+ * appear if the bd numbers is over than 20.
+ */
+#define NUM_BD 20
 
 struct sdma_engine;
 
@@ -1273,7 +1282,7 @@ static int sdma_alloc_chan_resources(struct dma_chan *chan)
 		goto disable_clk_ahb;
 
 	sdmac->bd_pool = dma_pool_create("bd_pool", chan->device->dev,
-				sizeof(struct sdma_buffer_descriptor),
+				NUM_BD * sizeof(struct sdma_buffer_descriptor),
 				32, 0);
 
 	return 0;
@@ -1314,6 +1323,12 @@ static struct sdma_desc *sdma_transfer_init(struct sdma_channel *sdmac,
 {
 	struct sdma_desc *desc;
 
+	if (bds > NUM_BD) {
+		dev_err(sdmac->sdma->dev, "%d bds exceed the max %d\n",
+			bds, NUM_BD);
+		goto err_out;
+	}
+
 	desc = kzalloc((sizeof(*desc)), GFP_NOWAIT);
 	if (!desc)
 		goto err_out;
-- 
2.7.4