dmaengine: altera: Use macros instead of structs to describe the registers

This patch moves from a struct declaration for the DMA controller
registers to macros with offests to the base address. This is mainly
done to remove the sparse warnings, since the function parameter of
ioread32/iowrite32 is "void __iomem *" instead of a pointer to struct
members. With this patch applied, no sparse warning is seen anymore.

Please note that the struct for the descriptors is still kept in place,
as the code largely accesses the struct members as internal variables
before the complete struct is copied into the descriptor FIFO of the
DMA controller.

Additionally this patch also removes two warnings "variable xxx set but
not used" seen when compiling with "W=1". The registers need to be read
to flush the response FIFO, but nothing needs to be done with them. So
the code is correct here and the warning is a false one.
Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/altera-msgdma.c

@@ -104,25 +104,14 @@ struct msgdma_extended_desc {
 #define MSGDMA_DESC_STRIDE_WR		0x00010000
 #define MSGDMA_DESC_STRIDE_RW		0x00010001
 
-/**
- * struct msgdma_csr - mSGDMA dispatcher control and status register map
- * @status: Read/Clear
- * @control: Read/Write
- * @rw_fill_level: bit 31:16 - write fill level
- *		   bit 15:00 - read fill level
- * @resp_fill_level: bit 15:00 - response FIFO fill level
- * @rw_seq_num: bit 31:16 - write sequence number
- *		bit 15:00 - read sequence number
- * @pad: reserved
- */
-struct msgdma_csr {
-	u32 status;
-	u32 control;
-	u32 rw_fill_level;
-	u32 resp_fill_level;
-	u32 rw_seq_num;
-	u32 pad[3];
-};
+/* mSGDMA dispatcher control and status register map */
+#define MSGDMA_CSR_STATUS		0x00	/* Read / Clear */
+#define MSGDMA_CSR_CONTROL		0x04	/* Read / Write */
+#define MSGDMA_CSR_RW_FILL_LEVEL	0x08	/* 31:16 - write fill level */
+						/* 15:00 - read fill level */
+#define MSGDMA_CSR_RESP_FILL_LEVEL	0x0c	/* response FIFO fill level */
+#define MSGDMA_CSR_RW_SEQ_NUM		0x10	/* 31:16 - write seq number */
+						/* 15:00 - read seq number */
 
 /* mSGDMA CSR status register bit definitions */
 #define MSGDMA_CSR_STAT_BUSY			BIT(0)
@@ -157,10 +146,8 @@ struct msgdma_csr {
 #define MSGDMA_CSR_SEQ_NUM_GET(v)		(((v) & 0xffff0000) >> 16)
 
 /* mSGDMA response register map */
-struct msgdma_response {
-	u32 bytes_transferred;
-	u32 status;
-};
+#define MSGDMA_RESP_BYTES_TRANSFERRED	0x00
+#define MSGDMA_RESP_STATUS		0x04
 
 /* mSGDMA response register bit definitions */
 #define MSGDMA_RESP_EARLY_TERM	BIT(8)
@@ -204,13 +191,13 @@ struct msgdma_device {
 	int irq;
 
 	/* mSGDMA controller */
-	struct msgdma_csr *csr;
+	void __iomem *csr;
 
 	/* mSGDMA descriptors */
-	struct msgdma_extended_desc *desc;
+	void __iomem *desc;
 
 	/* mSGDMA response */
-	struct msgdma_response *resp;
+	void __iomem *resp;
 };
 
 #define to_mdev(chan)	container_of(chan, struct msgdma_device, dmachan)
@@ -484,21 +471,21 @@ static void msgdma_reset(struct msgdma_device *mdev)
 	int ret;
 
 	/* Reset mSGDMA */
-	iowrite32(MSGDMA_CSR_STAT_MASK, &mdev->csr->status);
-	iowrite32(MSGDMA_CSR_CTL_RESET, &mdev->csr->control);
+	iowrite32(MSGDMA_CSR_STAT_MASK, mdev->csr + MSGDMA_CSR_STATUS);
+	iowrite32(MSGDMA_CSR_CTL_RESET, mdev->csr + MSGDMA_CSR_CONTROL);
 
-	ret = readl_poll_timeout(&mdev->csr->status, val,
+	ret = readl_poll_timeout(mdev->csr + MSGDMA_CSR_STATUS, val,
 				 (val & MSGDMA_CSR_STAT_RESETTING) == 0,
 				 1, 10000);
 	if (ret)
 		dev_err(mdev->dev, "DMA channel did not reset\n");
 
 	/* Clear all status bits */
-	iowrite32(MSGDMA_CSR_STAT_MASK, &mdev->csr->status);
+	iowrite32(MSGDMA_CSR_STAT_MASK, mdev->csr + MSGDMA_CSR_STATUS);
 
 	/* Enable the DMA controller including interrupts */
 	iowrite32(MSGDMA_CSR_CTL_STOP_ON_ERR | MSGDMA_CSR_CTL_STOP_ON_EARLY |
-		  MSGDMA_CSR_CTL_GLOBAL_INTR, &mdev->csr->control);
+		  MSGDMA_CSR_CTL_GLOBAL_INTR, mdev->csr + MSGDMA_CSR_CONTROL);
 
 	mdev->idle = true;
 };
@@ -506,13 +493,14 @@ static void msgdma_reset(struct msgdma_device *mdev)
 static void msgdma_copy_one(struct msgdma_device *mdev,
 			    struct msgdma_sw_desc *desc)
 {
-	struct msgdma_extended_desc *hw_desc = mdev->desc;
+	void __iomem *hw_desc = mdev->desc;
 
 	/*
 	 * Check if the DESC FIFO it not full. If its full, we need to wait
 	 * for at least one entry to become free again
 	 */
-	while (ioread32(&mdev->csr->status) & MSGDMA_CSR_STAT_DESC_BUF_FULL)
+	while (ioread32(mdev->csr + MSGDMA_CSR_STATUS) &
+	       MSGDMA_CSR_STAT_DESC_BUF_FULL)
 		mdelay(1);
 
 	/*
@@ -524,12 +512,14 @@ static void msgdma_copy_one(struct msgdma_device *mdev,
 	 * sure this control word is written last by single coding it and
 	 * adding some write-barriers here.
 	 */
-	memcpy(hw_desc, &desc->hw_desc, sizeof(desc->hw_desc) - sizeof(u32));
+	memcpy((void __force *)hw_desc, &desc->hw_desc,
+	       sizeof(desc->hw_desc) - sizeof(u32));
 
 	/* Write control word last to flush this descriptor into the FIFO */
 	mdev->idle = false;
 	wmb();
-	iowrite32(desc->hw_desc.control, &hw_desc->control);
+	iowrite32(desc->hw_desc.control, hw_desc +
+		  offsetof(struct msgdma_extended_desc, control));
 	wmb();
 }
 
@@ -690,13 +680,13 @@ static void msgdma_tasklet(unsigned long data)
 {
 	struct msgdma_device *mdev = (struct msgdma_device *)data;
 	u32 count;
-	u32 size;
-	u32 status;
+	u32 __maybe_unused size;
+	u32 __maybe_unused status;
 
 	spin_lock(&mdev->lock);
 
 	/* Read number of responses that are available */
-	count = ioread32(&mdev->csr->resp_fill_level);
+	count = ioread32(mdev->csr + MSGDMA_CSR_RESP_FILL_LEVEL);
 	dev_dbg(mdev->dev, "%s (%d): response count=%d\n",
 		__func__, __LINE__, count);
 
@@ -707,8 +697,8 @@ static void msgdma_tasklet(unsigned long data)
 		 * have any real values, like transferred bytes or error
 		 * bits. So we need to just drop these values.
 		 */
-		size = ioread32(&mdev->resp->bytes_transferred);
-		status = ioread32(&mdev->resp->status);
+		size = ioread32(mdev->resp + MSGDMA_RESP_BYTES_TRANSFERRED);
+		status = ioread32(mdev->resp - MSGDMA_RESP_STATUS);
 
 		msgdma_complete_descriptor(mdev);
 		msgdma_chan_desc_cleanup(mdev);
@@ -729,7 +719,7 @@ static irqreturn_t msgdma_irq_handler(int irq, void *data)
 	struct msgdma_device *mdev = data;
 	u32 status;
 
-	status = ioread32(&mdev->csr->status);
+	status = ioread32(mdev->csr + MSGDMA_CSR_STATUS);
 	if ((status & MSGDMA_CSR_STAT_BUSY) == 0) {
 		/* Start next transfer if the DMA controller is idle */
 		spin_lock(&mdev->lock);
@@ -741,7 +731,7 @@ static irqreturn_t msgdma_irq_handler(int irq, void *data)
 	tasklet_schedule(&mdev->irq_tasklet);
 
 	/* Clear interrupt in mSGDMA controller */
-	iowrite32(MSGDMA_CSR_STAT_IRQ, &mdev->csr->status);
+	iowrite32(MSGDMA_CSR_STAT_IRQ, mdev->csr + MSGDMA_CSR_STATUS);
 
 	return IRQ_HANDLED;
 }
@@ -809,17 +799,17 @@ static int msgdma_probe(struct platform_device *pdev)
 	mdev->dev = &pdev->dev;
 
 	/* Map CSR space */
-	ret = request_and_map(pdev, "csr", &dma_res, (void **)&mdev->csr);
+	ret = request_and_map(pdev, "csr", &dma_res, &mdev->csr);
 	if (ret)
 		return ret;
 
 	/* Map (extended) descriptor space */
-	ret = request_and_map(pdev, "desc", &dma_res, (void **)&mdev->desc);
+	ret = request_and_map(pdev, "desc", &dma_res, &mdev->desc);
 	if (ret)
 		return ret;
 
 	/* Map response space */
-	ret = request_and_map(pdev, "resp", &dma_res, (void **)&mdev->resp);
+	ret = request_and_map(pdev, "resp", &dma_res, &mdev->resp);
 	if (ret)
 		return ret;