ptp_qoriq: support automatic configuration for ptp timer

This patch is to support automatic configuration for ptp timer.
If required ptp dts properties are not provided, driver could
try to calculate a set of default configurations to initialize
the ptp timer. This makes the driver work for many boards which
don't have the required ptp dts properties in current kernel.
Also the users could set dts properties by themselves according
to their requirement.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_qoriq.c

@@ -29,6 +29,7 @@
 #include <linux/of_platform.h>
 #include <linux/timex.h>
 #include <linux/slab.h>
+#include <linux/clk.h>
 
 #include <linux/fsl/ptp_qoriq.h>
 
@@ -317,6 +318,105 @@ static const struct ptp_clock_info ptp_qoriq_caps = {
 	.enable		= ptp_qoriq_enable,
 };
 
+/**
+ * qoriq_ptp_nominal_freq - calculate nominal frequency according to
+ *			    reference clock frequency
+ *
+ * @clk_src: reference clock frequency
+ *
+ * The nominal frequency is the desired clock frequency.
+ * It should be less than the reference clock frequency.
+ * It should be a factor of 1000MHz.
+ *
+ * Return the nominal frequency
+ */
+static u32 qoriq_ptp_nominal_freq(u32 clk_src)
+{
+	u32 remainder = 0;
+
+	clk_src /= 1000000;
+	remainder = clk_src % 100;
+	if (remainder) {
+		clk_src -= remainder;
+		clk_src += 100;
+	}
+
+	do {
+		clk_src -= 100;
+
+	} while (1000 % clk_src);
+
+	return clk_src * 1000000;
+}
+
+/**
+ * qoriq_ptp_auto_config - calculate a set of default configurations
+ *
+ * @qoriq_ptp: pointer to qoriq_ptp
+ * @node: pointer to device_node
+ *
+ * If below dts properties are not provided, this function will be
+ * called to calculate a set of default configurations for them.
+ *   "fsl,tclk-period"
+ *   "fsl,tmr-prsc"
+ *   "fsl,tmr-add"
+ *   "fsl,tmr-fiper1"
+ *   "fsl,tmr-fiper2"
+ *   "fsl,max-adj"
+ *
+ * Return 0 if success
+ */
+static int qoriq_ptp_auto_config(struct qoriq_ptp *qoriq_ptp,
+				 struct device_node *node)
+{
+	struct clk *clk;
+	u64 freq_comp;
+	u64 max_adj;
+	u32 nominal_freq;
+	u32 clk_src = 0;
+
+	qoriq_ptp->cksel = DEFAULT_CKSEL;
+
+	clk = of_clk_get(node, 0);
+	if (!IS_ERR(clk)) {
+		clk_src = clk_get_rate(clk);
+		clk_put(clk);
+	}
+
+	if (clk_src <= 100000000UL) {
+		pr_err("error reference clock value, or lower than 100MHz\n");
+		return -EINVAL;
+	}
+
+	nominal_freq = qoriq_ptp_nominal_freq(clk_src);
+	if (!nominal_freq)
+		return -EINVAL;
+
+	qoriq_ptp->tclk_period = 1000000000UL / nominal_freq;
+	qoriq_ptp->tmr_prsc = DEFAULT_TMR_PRSC;
+
+	/* Calculate initial frequency compensation value for TMR_ADD register.
+	 * freq_comp = ceil(2^32 / freq_ratio)
+	 * freq_ratio = reference_clock_freq / nominal_freq
+	 */
+	freq_comp = ((u64)1 << 32) * nominal_freq;
+	if (do_div(freq_comp, clk_src))
+		freq_comp++;
+
+	qoriq_ptp->tmr_add = freq_comp;
+	qoriq_ptp->tmr_fiper1 = DEFAULT_FIPER1_PERIOD - qoriq_ptp->tclk_period;
+	qoriq_ptp->tmr_fiper2 = DEFAULT_FIPER2_PERIOD - qoriq_ptp->tclk_period;
+
+	/* max_adj = 1000000000 * (freq_ratio - 1.0) - 1
+	 * freq_ratio = reference_clock_freq / nominal_freq
+	 */
+	max_adj = 1000000000ULL * (clk_src - nominal_freq);
+	max_adj = max_adj / nominal_freq - 1;
+	qoriq_ptp->caps.max_adj = max_adj;
+
+	return 0;
+}
+
 static int qoriq_ptp_probe(struct platform_device *dev)
 {
 	struct device_node *node = dev->dev.of_node;
@@ -332,7 +432,7 @@ static int qoriq_ptp_probe(struct platform_device *dev)
 	if (!qoriq_ptp)
 		goto no_memory;
 
-	err = -ENODEV;
+	err = -EINVAL;
 
 	qoriq_ptp->caps = ptp_qoriq_caps;
 
@@ -351,10 +451,14 @@ static int qoriq_ptp_probe(struct platform_device *dev)
 				 "fsl,tmr-fiper2", &qoriq_ptp->tmr_fiper2) ||
 	    of_property_read_u32(node,
 				 "fsl,max-adj", &qoriq_ptp->caps.max_adj)) {
-		pr_err("device tree node missing required elements\n");
-		goto no_node;
+		pr_warn("device tree node missing required elements, try automatic configuration\n");
+
+		if (qoriq_ptp_auto_config(qoriq_ptp, node))
+			goto no_config;
 	}
 
+	err = -ENODEV;
+
 	qoriq_ptp->irq = platform_get_irq(dev, 0);
 
 	if (qoriq_ptp->irq < 0) {
@@ -436,6 +540,7 @@ static int qoriq_ptp_probe(struct platform_device *dev)
 	release_resource(qoriq_ptp->rsrc);
 no_resource:
 	free_irq(qoriq_ptp->irq, qoriq_ptp);
+no_config:
 no_node:
 	kfree(qoriq_ptp);
 no_memory:

include/linux/fsl/ptp_qoriq.h

@@ -127,9 +127,13 @@ struct qoriq_ptp_registers {
 
 
 #define DRIVER		"ptp_qoriq"
-#define DEFAULT_CKSEL	1
 #define N_EXT_TS	2
 
+#define DEFAULT_CKSEL		1
+#define DEFAULT_TMR_PRSC	2
+#define DEFAULT_FIPER1_PERIOD	1000000000
+#define DEFAULT_FIPER2_PERIOD	100000
+
 struct qoriq_ptp {
 	void __iomem *base;
 	struct qoriq_ptp_registers regs;