[RFC PATCH] i2c: imx: dma map the i2c data i/o register

[Laurentiu Tudor <laurentiu.tudor@nxp.com>]

This is an attempt to fix an iommu exception when doing dma to the
i2c controller with EDMA. Without these mappings the smmu raises a
context fault [1] exactly with the address of the i2c data i/o reg.
This was seen on an NXP LS1043A chip while working on enabling SMMU.

[1] arm-smmu 9000000.iommu: Unhandled context fault: fsr=0x402,
    iova=0x02180004, fsynr=0x150021, cb=7

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
---
 drivers/i2c/busses/i2c-imx.c | 57 +++++++++++++++++++++++++++++-------
 1 file changed, 47 insertions(+), 10 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 4e34b1572756..07cc8f4b45b9 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -202,6 +202,9 @@ struct imx_i2c_struct {
 	struct pinctrl_state *pinctrl_pins_gpio;
 
 	struct imx_i2c_dma	*dma;
+
+	dma_addr_t		dma_tx_addr;
+	dma_addr_t		dma_rx_addr;
 };
 
 static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
@@ -274,17 +277,20 @@ static inline unsigned char imx_i2c_read_reg(struct imx_i2c_struct *i2c_imx,
 
 /* Functions for DMA support */
 static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
-			       dma_addr_t phy_addr)
+			       phys_addr_t phy_addr)
 {
 	struct imx_i2c_dma *dma;
 	struct dma_slave_config dma_sconfig;
 	struct device *dev = &i2c_imx->adapter.dev;
 	int ret;
+	phys_addr_t i2dr_pa;
 
 	dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
 	if (!dma)
 		return -ENOMEM;
 
+	i2dr_pa = phy_addr + (IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
+
 	dma->chan_tx = dma_request_chan(dev, "tx");
 	if (IS_ERR(dma->chan_tx)) {
 		ret = PTR_ERR(dma->chan_tx);
@@ -293,15 +299,25 @@ static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
 		goto fail_al;
 	}
 
-	dma_sconfig.dst_addr = phy_addr +
-				(IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
+	i2c_imx->dma_tx_addr = dma_map_resource(dma->chan_tx->device->dev,
+						i2dr_pa,
+						DMA_SLAVE_BUSWIDTH_1_BYTE,
+						DMA_MEM_TO_DEV, 0);
+	ret = dma_mapping_error(dma->chan_tx->device->dev,
+				i2c_imx->dma_tx_addr);
+	if (ret) {
+		dev_err(dev, "can't dma map tx destination (%d)\n", ret);
+		goto fail_tx;
+	}
+
+	dma_sconfig.dst_addr = i2c_imx->dma_tx_addr;
 	dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
 	dma_sconfig.dst_maxburst = 1;
 	dma_sconfig.direction = DMA_MEM_TO_DEV;
 	ret = dmaengine_slave_config(dma->chan_tx, &dma_sconfig);
 	if (ret < 0) {
 		dev_err(dev, "can't configure tx channel (%d)\n", ret);
-		goto fail_tx;
+		goto fail_tx_dma;
 	}
 
 	dma->chan_rx = dma_request_chan(dev, "rx");
@@ -309,18 +325,28 @@ static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
 		ret = PTR_ERR(dma->chan_rx);
 		if (ret != -ENODEV && ret != -EPROBE_DEFER)
 			dev_err(dev, "can't request DMA rx channel (%d)\n", ret);
-		goto fail_tx;
+		goto fail_tx_dma;
 	}
 
-	dma_sconfig.src_addr = phy_addr +
-				(IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
+	i2c_imx->dma_rx_addr = dma_map_resource(dma->chan_rx->device->dev,
+						i2dr_pa,
+						DMA_SLAVE_BUSWIDTH_1_BYTE,
+						DMA_DEV_TO_MEM, 0);
+	ret = dma_mapping_error(dma->chan_rx->device->dev,
+				i2c_imx->dma_rx_addr);
+	if (ret) {
+		dev_err(dev, "can't dma map rx source (%d)\n", ret);
+		goto fail_rx;
+	}
+
+	dma_sconfig.src_addr = i2c_imx->dma_rx_addr;
 	dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
 	dma_sconfig.src_maxburst = 1;
 	dma_sconfig.direction = DMA_DEV_TO_MEM;
 	ret = dmaengine_slave_config(dma->chan_rx, &dma_sconfig);
 	if (ret < 0) {
 		dev_err(dev, "can't configure rx channel (%d)\n", ret);
-		goto fail_rx;
+		goto fail_rx_dma;
 	}
 
 	i2c_imx->dma = dma;
@@ -330,8 +356,14 @@ static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
 
 	return 0;
 
+fail_rx_dma:
+	dma_unmap_resource(dma->chan_rx->device->dev, i2c_imx->dma_rx_addr,
+			   DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_DEV_TO_MEM, 0);
 fail_rx:
 	dma_release_channel(dma->chan_rx);
+fail_tx_dma:
+	dma_unmap_resource(dma->chan_tx->device->dev, i2c_imx->dma_tx_addr,
+			   DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_MEM_TO_DEV, 0);
 fail_tx:
 	dma_release_channel(dma->chan_tx);
 fail_al:
@@ -1057,7 +1089,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	struct imxi2c_platform_data *pdata = dev_get_platdata(&pdev->dev);
 	void __iomem *base;
 	int irq, ret;
-	dma_addr_t phy_addr;
+	phys_addr_t phy_addr;
 
 	dev_dbg(&pdev->dev, "<%s>\n", __func__);
 
@@ -1072,7 +1104,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
-	phy_addr = (dma_addr_t)res->start;
+	phy_addr = res->start;
 	i2c_imx = devm_kzalloc(&pdev->dev, sizeof(*i2c_imx), GFP_KERNEL);
 	if (!i2c_imx)
 		return -ENOMEM;
@@ -1220,6 +1252,11 @@ static int i2c_imx_remove(struct platform_device *pdev)
 	pm_runtime_put_noidle(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 
+	dma_unmap_resource(&pdev->dev, i2c_imx->dma_tx_addr,
+			   DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_MEM_TO_DEV, 0);
+	dma_unmap_resource(&pdev->dev, i2c_imx->dma_rx_addr,
+			   DMA_SLAVE_BUSWIDTH_1_BYTE, DMA_DEV_TO_MEM, 0);
+
 	return 0;
 }
 
-- 
2.17.1