[PATCHv3 2/7] ARM: mvebu: extend PMSU code to support dynamic frequency scaling

Thomas Petazzoni
2014-07-09T15:45:22Z

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>
---
arch/arm/mach-mvebu/pmsu.c | 162 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/mvebu-pmsu.h | 20 ++++++
2 files changed, 182 insertions(+)
create mode 100644 include/linux/mvebu-pmsu.h

diff --git a/arch/arm/mach-mvebu/pmsu.c b/arch/arm/mach-mvebu/pmsu.c
index 53a55c8..db7d9ab 100644
--- a/arch/arm/mach-mvebu/pmsu.c
+++ b/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);
diff --git a/include/linux/mvebu-pmsu.h b/include/linux/mvebu-pmsu.h
new file mode 100644
index 0000000..b918d07
--- /dev/null
+++ b/include/linux/mvebu-pmsu.h
@@ -0,0 +1,20 @@
+/*
+ * 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__ */
--
2.0.0