[PATCH v2 16/24] net: can: mscan: make mpc512x code use common clock

[Gerhard Sittig]

extend the mscan(4) driver with alternative support for the COMMON_CLK
approach which is an option in the MPC512x platform, keep the existing
clock support implementation in place since the driver is shared with
other MPC5xxx SoCs which don't have common clock support

one byproduct of this change is that the CAN driver no longer needs to
access the SoC's clock control registers, which shall be the domain of
the platform's clock driver

Signed-off-by: Gerhard Sittig <gsi at denx.de>
---
 drivers/net/can/mscan/mpc5xxx_can.c |  139 +++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)

diff --git a/drivers/net/can/mscan/mpc5xxx_can.c b/drivers/net/can/mscan/mpc5xxx_can.c
index bc422ba..dd26ab6 100644
--- a/drivers/net/can/mscan/mpc5xxx_can.c
+++ b/drivers/net/can/mscan/mpc5xxx_can.c
@@ -108,6 +108,143 @@ static u32 mpc52xx_can_get_clock(struct platform_device *ofdev,
 #endif /* CONFIG_PPC_MPC52xx */
 
 #ifdef CONFIG_PPC_MPC512x
+
+#if IS_ENABLED(CONFIG_COMMON_CLK)
+
+static u32 mpc512x_can_get_clock(struct platform_device *ofdev,
+				 const char *clock_source, int *mscan_clksrc)
+{
+	struct device_node *np;
+	u32 clockdiv;
+	enum {
+		CLK_FROM_AUTO,
+		CLK_FROM_IPS,
+		CLK_FROM_SYS,
+		CLK_FROM_REF,
+	} clk_from;
+	struct clk *clk_in, *clk_can;
+	unsigned long freq_calc;
+
+	/* the caller passed in the clock source spec that was read from
+	 * the device tree, get the optional clock divider as well
+	 */
+	np = ofdev->dev.of_node;
+	clockdiv = 1;
+	of_property_read_u32(np, "fsl,mscan-clock-divider", &clockdiv);
+	dev_dbg(&ofdev->dev, "device tree specs: clk src[%s] div[%d]\n",
+		clock_source ? clock_source : "<NULL>", clockdiv);
+
+	/* when clock-source is 'ip', the CANCTL1[CLKSRC] bit needs to
+	 * get set, and the 'ips' clock is the input to the MSCAN
+	 * component
+	 *
+	 * for clock-source values of 'ref' or 'sys' the CANCTL1[CLKSRC]
+	 * bit needs to get cleared, an optional clock-divider may have
+	 * been specified (the default value is 1), the appropriate
+	 * MSCAN related MCLK is the input to the MSCAN component
+	 *
+	 * in the absence of a clock-source spec, first an optimal clock
+	 * gets determined based on the 'sys' clock, if that fails the
+	 * 'ref' clock is used
+	 */
+	clk_from = CLK_FROM_AUTO;
+	if (clock_source) {
+		/* interpret the device tree's spec for the clock source */
+		if (!strcmp(clock_source, "ip"))
+			clk_from = CLK_FROM_IPS;
+		else if (!strcmp(clock_source, "sys"))
+			clk_from = CLK_FROM_SYS;
+		else if (!strcmp(clock_source, "ref"))
+			clk_from = CLK_FROM_REF;
+		else
+			goto err_invalid;
+		dev_dbg(&ofdev->dev, "got a clk source spec[%d]\n", clk_from);
+	}
+	if (clk_from == CLK_FROM_AUTO) {
+		/* no spec so far, try the 'sys' clock; round to the
+		 * next MHz and see if we can get a multiple of 16MHz
+		 */
+		dev_dbg(&ofdev->dev, "no clk source spec, trying SYS\n");
+		clk_in = clk_get(&ofdev->dev, "sys");
+		if (IS_ERR(clk_in))
+			goto err_notavail;
+		freq_calc = clk_get_rate(clk_in);
+		freq_calc +=  499999;
+		freq_calc /= 1000000;
+		freq_calc *= 1000000;
+		if ((freq_calc % 16000000) == 0) {
+			clk_from = CLK_FROM_SYS;
+			clockdiv = freq_calc / 16000000;
+			dev_dbg(&ofdev->dev,
+				"clk fit, sys[%lu] div[%d] freq[%lu]\n",
+				freq_calc, clockdiv, freq_calc / clockdiv);
+		}
+	}
+	if (clk_from == CLK_FROM_AUTO) {
+		/* no spec so far, use the 'ref' clock */
+		dev_dbg(&ofdev->dev, "no clk source spec, trying REF\n");
+		clk_in = clk_get(&ofdev->dev, "ref");
+		if (IS_ERR(clk_in))
+			goto err_notavail;
+		clk_from = CLK_FROM_REF;
+		freq_calc = clk_get_rate(clk_in);
+		dev_dbg(&ofdev->dev,
+			"clk fit, ref[%lu] (no div) freq[%lu]\n",
+			freq_calc, freq_calc);
+	}
+
+	/* select IPS or MCLK as the MSCAN input (returned to the caller),
+	 * setup the MCLK mux source and rate if applicable, apply the
+	 * optionally specified or derived above divider, and determine
+	 * the actual resulting clock rate to return to the caller
+	 */
+	switch (clk_from) {
+	case CLK_FROM_IPS:
+		clk_can = clk_get(&ofdev->dev, "ips");
+		if (IS_ERR(clk_can))
+			goto err_notavail;
+		clk_prepare_enable(clk_can);
+		freq_calc = clk_get_rate(clk_can);
+		*mscan_clksrc = MSCAN_CLKSRC_IPS;
+		dev_dbg(&ofdev->dev, "clk from IPS, clksrc[%d] freq[%lu]\n",
+			*mscan_clksrc, freq_calc);
+		break;
+	case CLK_FROM_SYS:
+	case CLK_FROM_REF:
+		clk_can = clk_get(&ofdev->dev, "mclk");
+		if (IS_ERR(clk_can))
+			goto err_notavail;
+		clk_prepare_enable(clk_can);
+		if (clk_from == CLK_FROM_SYS)
+			clk_in = clk_get(&ofdev->dev, "sys");
+		if (clk_from == CLK_FROM_REF)
+			clk_in = clk_get(&ofdev->dev, "ref");
+		if (IS_ERR(clk_in))
+			goto err_notavail;
+		clk_set_parent(clk_can, clk_in);
+		freq_calc = clk_get_rate(clk_in);
+		freq_calc /= clockdiv;
+		clk_set_rate(clk_can, freq_calc);
+		freq_calc = clk_get_rate(clk_can);
+		*mscan_clksrc = MSCAN_CLKSRC_BUS;
+		dev_dbg(&ofdev->dev, "clk from MCLK, clksrc[%d] freq[%lu]\n",
+			*mscan_clksrc, freq_calc);
+		break;
+	default:
+		goto err_invalid;
+	}
+
+	return freq_calc;
+
+err_invalid:
+	dev_err(&ofdev->dev, "invalid clock source specification\n");
+	return 0;
+
+err_notavail:
+	dev_err(&ofdev->dev, "cannot acquire or setup clock source\n");
+	return 0;
+}
+#else	/* COMMON_CLK */
 struct mpc512x_clockctl {
 	u32 spmr;		/* System PLL Mode Reg */
 	u32 sccr[2];		/* System Clk Ctrl Reg 1 & 2 */
@@ -238,6 +375,8 @@ exit_put:
 	of_node_put(np_clock);
 	return freq;
 }
+#endif	/* COMMON_CLK */
+
 #else /* !CONFIG_PPC_MPC512x */
 static u32 mpc512x_can_get_clock(struct platform_device *ofdev,
 				 const char *clock_name, int *mscan_clksrc)
-- 
1.7.10.4