ARM: mvebu: extend PMSU code to support dynamic frequency scaling

This commit adds the necessary code in the Marvell EBU PMSU driver to
support dynamic frequency scaling. In essence, what this new code does
is that it:

 * registers the frequency operating points supported by the CPU;

 * registers a clock notifier of the CPU clocks. The notifier function
   listens to the newly introduced APPLY_RATE_CHANGE event, and uses
   that to finalize the frequency transition by doing the part of the
   procedure that involves the PMSU;

 * registers a platform device for the cpufreq-generic driver, which
   will take care of the CPU frequency transitions.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1404920715-19834-3-git-send-email-thomas.petazzoni@free-electrons.comSigned-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/mach-mvebu/pmsu.c

@@ -18,20 +18,26 @@
 
 #define pr_fmt(fmt) "mvebu-pmsu: " fmt
 
+#include <linux/clk.h>
 #include <linux/cpu_pm.h>
+#include <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/of_address.h>
+#include <linux/of_device.h>
 #include <linux/io.h>
 #include <linux/platform_device.h>
+#include <linux/pm_opp.h>
 #include <linux/smp.h>
 #include <linux/resource.h>
+#include <linux/slab.h>
 #include <asm/cacheflush.h>
 #include <asm/cp15.h>
 #include <asm/smp_plat.h>
 #include <asm/suspend.h>
 #include <asm/tlbflush.h>
 #include "common.h"
+#include "armada-370-xp.h"
 
 static void __iomem *pmsu_mp_base;
 
@@ -57,6 +63,10 @@ static void __iomem *pmsu_mp_base;
 #define PMSU_STATUS_AND_MASK_IRQ_MASK		BIT(24)
 #define PMSU_STATUS_AND_MASK_FIQ_MASK		BIT(25)
 
+#define PMSU_EVENT_STATUS_AND_MASK(cpu)     ((cpu * 0x100) + 0x120)
+#define PMSU_EVENT_STATUS_AND_MASK_DFS_DONE        BIT(1)
+#define PMSU_EVENT_STATUS_AND_MASK_DFS_DONE_MASK   BIT(17)
+
 #define PMSU_BOOT_ADDR_REDIRECT_OFFSET(cpu) ((cpu * 0x100) + 0x124)
 
 /* PMSU fabric registers */
@@ -296,3 +306,155 @@ int __init armada_370_xp_cpu_pm_init(void)
 
 arch_initcall(armada_370_xp_cpu_pm_init);
 early_initcall(armada_370_xp_pmsu_init);
+
+static void mvebu_pmsu_dfs_request_local(void *data)
+{
+	u32 reg;
+	u32 cpu = smp_processor_id();
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	/* Prepare to enter idle */
+	reg = readl(pmsu_mp_base + PMSU_STATUS_AND_MASK(cpu));
+	reg |= PMSU_STATUS_AND_MASK_CPU_IDLE_WAIT |
+	       PMSU_STATUS_AND_MASK_IRQ_MASK     |
+	       PMSU_STATUS_AND_MASK_FIQ_MASK;
+	writel(reg, pmsu_mp_base + PMSU_STATUS_AND_MASK(cpu));
+
+	/* Request the DFS transition */
+	reg = readl(pmsu_mp_base + PMSU_CONTROL_AND_CONFIG(cpu));
+	reg |= PMSU_CONTROL_AND_CONFIG_DFS_REQ;
+	writel(reg, pmsu_mp_base + PMSU_CONTROL_AND_CONFIG(cpu));
+
+	/* The fact of entering idle will trigger the DFS transition */
+	wfi();
+
+	/*
+	 * We're back from idle, the DFS transition has completed,
+	 * clear the idle wait indication.
+	 */
+	reg = readl(pmsu_mp_base + PMSU_STATUS_AND_MASK(cpu));
+	reg &= ~PMSU_STATUS_AND_MASK_CPU_IDLE_WAIT;
+	writel(reg, pmsu_mp_base + PMSU_STATUS_AND_MASK(cpu));
+
+	local_irq_restore(flags);
+}
+
+int mvebu_pmsu_dfs_request(int cpu)
+{
+	unsigned long timeout;
+	int hwcpu = cpu_logical_map(cpu);
+	u32 reg;
+
+	/* Clear any previous DFS DONE event */
+	reg = readl(pmsu_mp_base + PMSU_EVENT_STATUS_AND_MASK(hwcpu));
+	reg &= ~PMSU_EVENT_STATUS_AND_MASK_DFS_DONE;
+	writel(reg, pmsu_mp_base + PMSU_EVENT_STATUS_AND_MASK(hwcpu));
+
+	/* Mask the DFS done interrupt, since we are going to poll */
+	reg = readl(pmsu_mp_base + PMSU_EVENT_STATUS_AND_MASK(hwcpu));
+	reg |= PMSU_EVENT_STATUS_AND_MASK_DFS_DONE_MASK;
+	writel(reg, pmsu_mp_base + PMSU_EVENT_STATUS_AND_MASK(hwcpu));
+
+	/* Trigger the DFS on the appropriate CPU */
+	smp_call_function_single(cpu, mvebu_pmsu_dfs_request_local,
+				 NULL, false);
+
+	/* Poll until the DFS done event is generated */
+	timeout = jiffies + HZ;
+	while (time_before(jiffies, timeout)) {
+		reg = readl(pmsu_mp_base + PMSU_EVENT_STATUS_AND_MASK(hwcpu));
+		if (reg & PMSU_EVENT_STATUS_AND_MASK_DFS_DONE)
+			break;
+		udelay(10);
+	}
+
+	if (time_after(jiffies, timeout))
+		return -ETIME;
+
+	/* Restore the DFS mask to its original state */
+	reg = readl(pmsu_mp_base + PMSU_EVENT_STATUS_AND_MASK(hwcpu));
+	reg &= ~PMSU_EVENT_STATUS_AND_MASK_DFS_DONE_MASK;
+	writel(reg, pmsu_mp_base + PMSU_EVENT_STATUS_AND_MASK(hwcpu));
+
+	return 0;
+}
+
+static int __init armada_xp_pmsu_cpufreq_init(void)
+{
+	struct device_node *np;
+	struct resource res;
+	int ret, cpu;
+
+	if (!of_machine_is_compatible("marvell,armadaxp"))
+		return 0;
+
+	/*
+	 * In order to have proper cpufreq handling, we need to ensure
+	 * that the Device Tree description of the CPU clock includes
+	 * the definition of the PMU DFS registers. If not, we do not
+	 * register the clock notifier and the cpufreq driver. This
+	 * piece of code is only for compatibility with old Device
+	 * Trees.
+	 */
+	np = of_find_compatible_node(NULL, NULL, "marvell,armada-xp-cpu-clock");
+	if (!np)
+		return 0;
+
+	ret = of_address_to_resource(np, 1, &res);
+	if (ret) {
+		pr_warn(FW_WARN "not enabling cpufreq, deprecated armada-xp-cpu-clock binding\n");
+		of_node_put(np);
+		return 0;
+	}
+
+	of_node_put(np);
+
+	/*
+	 * For each CPU, this loop registers the operating points
+	 * supported (which are the nominal CPU frequency and half of
+	 * it), and registers the clock notifier that will take care
+	 * of doing the PMSU part of a frequency transition.
+	 */
+	for_each_possible_cpu(cpu) {
+		struct device *cpu_dev;
+		struct clk *clk;
+		int ret;
+
+		cpu_dev = get_cpu_device(cpu);
+		if (!cpu_dev) {
+			pr_err("Cannot get CPU %d\n", cpu);
+			continue;
+		}
+
+		clk = clk_get(cpu_dev, 0);
+		if (!clk) {
+			pr_err("Cannot get clock for CPU %d\n", cpu);
+			return -ENODEV;
+		}
+
+		/*
+		 * In case of a failure of dev_pm_opp_add(), we don't
+		 * bother with cleaning up the registered OPP (there's
+		 * no function to do so), and simply cancel the
+		 * registration of the cpufreq device.
+		 */
+		ret = dev_pm_opp_add(cpu_dev, clk_get_rate(clk), 0);
+		if (ret) {
+			clk_put(clk);
+			return ret;
+		}
+
+		ret = dev_pm_opp_add(cpu_dev, clk_get_rate(clk) / 2, 0);
+		if (ret) {
+			clk_put(clk);
+			return ret;
+		}
+	}
+
+	platform_device_register_simple("cpufreq-generic", -1, NULL, 0);
+	return 0;
+}
+
+device_initcall(armada_xp_pmsu_cpufreq_init);

include/linux/mvebu-pmsu.h

+/*
+ * Copyright (C) 2012 Marvell
+ *
+ * Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifndef __MVEBU_PMSU_H__
+#define __MVEBU_PMSU_H__
+
+#ifdef CONFIG_MACH_MVEBU_V7
+int mvebu_pmsu_dfs_request(int cpu);
+#else
+static inline int mvebu_pmsu_dfs_request(int cpu) { return -ENODEV; }
+#endif
+
+#endif /* __MVEBU_PMSU_H__ */