[PATCH v2 2/3] dma: imx-sdma: add clock ratio 1:1 check

[Angus Ainslie (Purism)]

On i.mx8 mscale B0 chip, AHB/SDMA clock ratio 2:1 can't be supportted,
since SDMA clock ratio has to be increased to 250Mhz, AHB can't reach
to 500Mhz, so use 1:1 instead.

based on NXP commit MLK-16841-1

Signed-off-by: Angus Ainslie (Purism) <angus@xxxxxxxx>
---
 .../devicetree/bindings/dma/fsl-imx-sdma.txt  |  1 +
 drivers/dma/imx-sdma.c                        | 20 +++++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt b/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
index 3c9a57a8443b..17544c1820b7 100644
--- a/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
+++ b/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
@@ -67,6 +67,7 @@ Optional properties:
     reg is the GPR register offset.
     shift is the bit position inside the GPR register.
     val is the value of the bit (0 or 1).
+- fsl,ratio-1-1: AHB/SDMA core clock ration 1:1, 2:1 without this.
 
 Examples:
 
diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index 0b3a67ff8e82..65dada21d3c1 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -440,6 +440,8 @@ struct sdma_engine {
 	unsigned int			irq;
 	dma_addr_t			bd0_phys;
 	struct sdma_buffer_descriptor	*bd0;
+	/* clock ratio for AHB:SDMA core. 1:1 is 1, 2:1 is 0*/
+	bool				clk_ratio;
 };
 
 static int sdma_config_write(struct dma_chan *chan,
@@ -662,8 +664,14 @@ static int sdma_run_channel0(struct sdma_engine *sdma)
 		dev_err(sdma->dev, "Timeout waiting for CH0 ready\n");
 
 	/* Set bits of CONFIG register with dynamic context switching */
-	if (readl(sdma->regs + SDMA_H_CONFIG) == 0)
-		writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG);
+	if (readl(sdma->regs + SDMA_H_CONFIG) == 0) {
+		if (sdma->clk_ratio)
+			reg = SDMA_H_CONFIG_CSM | SDMA_H_CONFIG_ACR;
+		else
+			reg = SDMA_H_CONFIG_CSM;
+
+		writel_relaxed(reg, sdma->regs + SDMA_H_CONFIG);
+	}
 
 	return ret;
 }
@@ -1880,8 +1888,10 @@ static int sdma_init(struct sdma_engine *sdma)
 	writel_relaxed(0x4050, sdma->regs + SDMA_CHN0ADDR);
 
 	/* Set bits of CONFIG register but with static context switching */
-	/* FIXME: Check whether to set ACR bit depending on clock ratios */
-	writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
+	if (sdma->clk_ratio)
+		writel_relaxed(SDMA_H_CONFIG_ACR, sdma->regs + SDMA_H_CONFIG);
+	else
+		writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
 
 	writel_relaxed(ccb_phys, sdma->regs + SDMA_H_C0PTR);
 
@@ -1975,6 +1985,8 @@ static int sdma_probe(struct platform_device *pdev)
 	if (!sdma)
 		return -ENOMEM;
 
+	sdma->clk_ratio = of_property_read_bool(np, "fsl,ratio-1-1");
+
 	spin_lock_init(&sdma->channel_0_lock);
 
 	sdma->dev = &pdev->dev;
-- 
2.17.1