linux-kernel - [PATCH 5/6] dmaengine: xilinx_dma: autodetect whether the HW supports scatter-gather

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Message-Id: <20180620083653.17010-5-andrea.merello@gmail.com>
Date:   Wed, 20 Jun 2018 10:36:52 +0200
From:   Andrea Merello <andrea.merello@...il.com>
To:     vkoul@...nel.org, dan.j.williams@...el.com,
        michal.simek@...inx.com, appana.durga.rao@...inx.com,
        dmaengine@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Andrea Merello <andrea.merello@...il.com>
Subject: [PATCH 5/6] dmaengine: xilinx_dma: autodetect whether the HW supports scatter-gather

The HW can be either direct-access or scatter-gather version. These are
SW incompatible.

The driver can handle both version: a DT property was used to
tell the driver whether to assume the HW is is scatter-gather mode.

This patch makes the driver to autodetect this information. The DT
property is not required anymore.

Signed-off-by: Andrea Merello <andrea.merello@...il.com>
---
 drivers/dma/xilinx/xilinx_dma.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index bdbc8ba9092a..8c6e818e596f 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -86,6 +86,7 @@
 #define XILINX_DMA_DMASR_DMA_DEC_ERR		BIT(6)
 #define XILINX_DMA_DMASR_DMA_SLAVE_ERR		BIT(5)
 #define XILINX_DMA_DMASR_DMA_INT_ERR		BIT(4)
+#define XILINX_DMA_DMASR_SG_MASK		BIT(3)
 #define XILINX_DMA_DMASR_IDLE			BIT(1)
 #define XILINX_DMA_DMASR_HALTED		BIT(0)
 #define XILINX_DMA_DMASR_DELAY_MASK		GENMASK(31, 24)
@@ -407,7 +408,6 @@ struct xilinx_dma_config {
  * @dev: Device Structure
  * @common: DMA device structure
  * @chan: Driver specific DMA channel
- * @has_sg: Specifies whether Scatter-Gather is present or not
  * @mcdma: Specifies whether Multi-Channel is present or not
  * @flush_on_fsync: Flush on frame sync
  * @ext_addr: Indicates 64 bit addressing is supported by dma device
@@ -426,7 +426,6 @@ struct xilinx_dma_device {
 	struct device *dev;
 	struct dma_device common;
 	struct xilinx_dma_chan *chan[XILINX_DMA_MAX_CHANS_PER_DEVICE];
-	bool has_sg;
 	bool mcdma;
 	u32 flush_on_fsync;
 	bool ext_addr;
@@ -2391,7 +2390,6 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
 
 	chan->dev = xdev->dev;
 	chan->xdev = xdev;
-	chan->has_sg = xdev->has_sg;
 	chan->desc_pendingcount = 0x0;
 	chan->ext_addr = xdev->ext_addr;
 	/* This variable ensures that descriptors are not
@@ -2488,6 +2486,13 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
 		chan->stop_transfer = xilinx_dma_stop_transfer;
 	}
 
+	/* check if SG is enabled */
+	if (dma_ctrl_read(chan, XILINX_DMA_REG_DMASR) &
+		XILINX_DMA_DMASR_SG_MASK)
+		chan->has_sg = true;
+	dev_dbg(chan->dev, "ch %d: SG %s\n", chan->id,
+		chan->has_sg ? "enabled" : "disabled");
+
 	/* Initialize the tasklet */
 	tasklet_init(&chan->tasklet, xilinx_dma_do_tasklet,
 			(unsigned long)chan);
@@ -2626,7 +2631,6 @@ static int xilinx_dma_probe(struct platform_device *pdev)
 		return PTR_ERR(xdev->regs);
 
 	/* Retrieve the DMA engine properties from the device tree */
-
 	if (xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
 		xdev->mcdma = of_property_read_bool(node, "xlnx,mcdma");
 		err = of_property_read_u32(node, "xlnx,lengthregwidth",
-- 
2.17.1