can: flexcan: add support for PE clock source select

Add support to select the clock source for CAN Protocol Engine (PE).
It's SoC Implementation dependent. Refer to RM for detailed definition
of each SoC. We select clock source 1 (peripheral clock) by default in
driver now, this patch adds support to parse the clock source from the DT.

Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/flexcan.c

@@ -275,6 +275,8 @@ struct flexcan_priv {
 	u8 tx_mb_idx;
 	u8 mb_count;
 	u8 mb_size;
+	u8 clk_src;	/* clock source of CAN Protocol Engine */
+
 	u32 reg_ctrl_default;
 	u32 reg_imask1_default;
 	u32 reg_imask2_default;
@@ -1369,7 +1371,10 @@ static int register_flexcandev(struct net_device *dev)
 		goto out_clks_disable;
 
 	reg = priv->read(&regs->ctrl);
-	reg |= FLEXCAN_CTRL_CLK_SRC;
+	if (priv->clk_src)
+		reg |= FLEXCAN_CTRL_CLK_SRC;
+	else
+		reg &= ~FLEXCAN_CTRL_CLK_SRC;
 	priv->write(reg, &regs->ctrl);
 
 	err = flexcan_chip_enable(priv);
@@ -1501,6 +1506,7 @@ static int flexcan_probe(struct platform_device *pdev)
 	struct clk *clk_ipg = NULL, *clk_per = NULL;
 	struct flexcan_regs __iomem *regs;
 	int err, irq;
+	u8 clk_src = 1;
 	u32 clock_freq = 0;
 
 	reg_xceiver = devm_regulator_get(&pdev->dev, "xceiver");
@@ -1509,9 +1515,12 @@ static int flexcan_probe(struct platform_device *pdev)
 	else if (IS_ERR(reg_xceiver))
 		reg_xceiver = NULL;
 
-	if (pdev->dev.of_node)
+	if (pdev->dev.of_node) {
 		of_property_read_u32(pdev->dev.of_node,
 				     "clock-frequency", &clock_freq);
+		of_property_read_u8(pdev->dev.of_node,
+				    "fsl,clk-source", &clk_src);
+	}
 
 	if (!clock_freq) {
 		clk_ipg = devm_clk_get(&pdev->dev, "ipg");
@@ -1580,6 +1589,7 @@ static int flexcan_probe(struct platform_device *pdev)
 	priv->regs = regs;
 	priv->clk_ipg = clk_ipg;
 	priv->clk_per = clk_per;
+	priv->clk_src = clk_src;
 	priv->devtype_data = devtype_data;
 	priv->reg_xceiver = reg_xceiver;