xtensa: rearrange CCOUNT calibration

DT-enabled kernel should have a CPU node connected to a clock. This clock
is the CCOUNT clock. Use old platform_calibrate_ccount call as a fallback
when CPU node cannot be found or has no clock and in non-DT-enabled
configurations.

Drop no longer needed code that updates CPU clock-frequency property in
the DT; drop DT-related code from the platform_calibrate_ccount too.

Move of_clk_init to the top of time_init, so that clocks are initialized
before CCOUNT calibration is attempted.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/boot/dts/xtfpga.dtsi

@@ -19,9 +19,7 @@ cpus {
 		cpu@0 {
 			compatible = "cdns,xtensa-cpu";
 			reg = <0>;
-			/* Filled in by platform_setup from FPGA register
-			 * clock-frequency = <100000000>;
-			 */
+			clocks = <&osc>;
 		};
 	};
 

arch/xtensa/kernel/setup.c

@@ -23,7 +23,6 @@
 #include <linux/bootmem.h>
 #include <linux/kernel.h>
 #include <linux/percpu.h>
-#include <linux/clk-provider.h>
 #include <linux/cpu.h>
 #include <linux/of.h>
 #include <linux/of_fdt.h>
@@ -249,7 +248,6 @@ void __init early_init_devtree(void *params)
 
 static int __init xtensa_device_probe(void)
 {
-	of_clk_init(NULL);
 	of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
 	return 0;
 }

arch/xtensa/kernel/time.c

@@ -12,6 +12,8 @@
  * Chris Zankel <chris@zankel.net>
  */
 
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
 #include <linux/time.h>
@@ -134,16 +136,52 @@ void local_timer_setup(unsigned cpu)
 					0xf, 0xffffffff);
 }
 
+#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
+#ifdef CONFIG_OF
+static void __init calibrate_ccount(void)
+{
+	struct device_node *cpu;
+	struct clk *clk;
+
+	cpu = of_find_compatible_node(NULL, NULL, "cdns,xtensa-cpu");
+	if (cpu) {
+		clk = of_clk_get(cpu, 0);
+		if (!IS_ERR(clk)) {
+			ccount_freq = clk_get_rate(clk);
+			return;
+		} else {
+			pr_warn("%s: CPU input clock not found\n",
+				__func__);
+		}
+	} else {
+		pr_warn("%s: CPU node not found in the device tree\n",
+			__func__);
+	}
+
+	platform_calibrate_ccount();
+}
+#else
+static inline void calibrate_ccount(void)
+{
+	platform_calibrate_ccount();
+}
+#endif
+#endif
+
 void __init time_init(void)
 {
+	of_clk_init(NULL);
 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
 	printk("Calibrating CPU frequency ");
-	platform_calibrate_ccount();
+	calibrate_ccount();
 	printk("%d.%02d MHz\n", (int)ccount_freq/1000000,
 			(int)(ccount_freq/10000)%100);
 #else
 	ccount_freq = CONFIG_XTENSA_CPU_CLOCK*1000000UL;
 #endif
+	WARN(!ccount_freq,
+	     "%s: CPU clock frequency is not set up correctly\n",
+	     __func__);
 	clocksource_register_hz(&ccount_clocksource, ccount_freq);
 	local_timer_setup(0);
 	setup_irq(this_cpu_ptr(&ccount_timer)->evt.irq, &timer_irqaction);

arch/xtensa/platforms/xtfpga/setup.c

@@ -66,29 +66,6 @@ void __init platform_setup(char **cmdline)
 
 #ifdef CONFIG_OF
 
-static void __init update_clock_frequency(struct device_node *node)
-{
-	struct property *newfreq;
-	u32 freq;
-
-	if (!of_property_read_u32(node, "clock-frequency", &freq) && freq != 0)
-		return;
-
-	newfreq = kzalloc(sizeof(*newfreq) + sizeof(u32), GFP_KERNEL);
-	if (!newfreq)
-		return;
-	newfreq->value = newfreq + 1;
-	newfreq->length = sizeof(freq);
-	newfreq->name = kstrdup("clock-frequency", GFP_KERNEL);
-	if (!newfreq->name) {
-		kfree(newfreq);
-		return;
-	}
-
-	*(u32 *)newfreq->value = cpu_to_be32(*(u32 *)XTFPGA_CLKFRQ_VADDR);
-	of_update_property(node, newfreq);
-}
-
 static void __init xtfpga_clk_setup(struct device_node *np)
 {
 	void __iomem *base = of_iomap(np, 0);
@@ -172,21 +149,7 @@ void platform_heartbeat(void)
 
 void __init platform_calibrate_ccount(void)
 {
-	long clk_freq = 0;
-#ifdef CONFIG_OF
-	struct device_node *cpu =
-		of_find_compatible_node(NULL, NULL, "cdns,xtensa-cpu");
-	if (cpu) {
-		u32 freq;
-		update_clock_frequency(cpu);
-		if (!of_property_read_u32(cpu, "clock-frequency", &freq))
-			clk_freq = freq;
-	}
-#endif
-	if (!clk_freq)
-		clk_freq = *(long *)XTFPGA_CLKFRQ_VADDR;
-
-	ccount_freq = clk_freq;
+	ccount_freq = *(long *)XTFPGA_CLKFRQ_VADDR;
 }
 
 #endif