Re: [PATCH 2/6] clocksource: tegra: add Tegra210 timer driver

From: Joseph Lo
Date: Thu Jan 24 2019 - 23:12:36 EST

On 1/24/19 7:09 PM, Jon Hunter wrote:

On 07/01/2019 03:28, Joseph Lo wrote:
Add support for the Tegra210 timer that runs at oscillator clock
(TMR10-TMR13). We need these timers to work as clock event device and to
replace the ARMv8 architected timer due to it can't survive across the
power cycle of the CPU core or CPUPORESET signal. So it can't be a wake-up
source when CPU suspends in power down state.

Based on the work of Antti P Miettinen <amiettinen@xxxxxxxxxx>

Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Joseph Lo <josephl@xxxxxxxxxx>
---
drivers/clocksource/Kconfig | 3 +
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-tegra210.c | 240 +++++++++++++++++++++++++++
include/linux/cpuhotplug.h | 1 +
4 files changed, 245 insertions(+)
create mode 100644 drivers/clocksource/timer-tegra210.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index a9e26f6a81a1..e6e3e64b6320 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -135,6 +135,9 @@ config TEGRA_TIMER
help
Enables support for the Tegra driver.
+config TEGRA210_TIMER
+ def_bool ARCH_TEGRA_210_SOC
+
config VT8500_TIMER
bool "VT8500 timer driver" if COMPILE_TEST
depends on HAS_IOMEM
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index cdd210ff89ea..95de59c8a47b 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_SUN4I_TIMER) += timer-sun4i.o
obj-$(CONFIG_SUN5I_HSTIMER) += timer-sun5i.o
obj-$(CONFIG_MESON6_TIMER) += timer-meson6.o
obj-$(CONFIG_TEGRA_TIMER) += timer-tegra20.o
+obj-$(CONFIG_TEGRA210_TIMER) += timer-tegra210.o
obj-$(CONFIG_VT8500_TIMER) += timer-vt8500.o
obj-$(CONFIG_NSPIRE_TIMER) += timer-zevio.o
obj-$(CONFIG_BCM_KONA_TIMER) += bcm_kona_timer.o
diff --git a/drivers/clocksource/timer-tegra210.c b/drivers/clocksource/timer-tegra210.c
new file mode 100644
index 000000000000..d88c127d3b3b
--- /dev/null
+++ b/drivers/clocksource/timer-tegra210.c
@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2014-2019, NVIDIA CORPORATION. All rights reserved.
+ */
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/percpu.h>
+#include <linux/syscore_ops.h>
+
+static u32 tegra210_timer_freq;
+static void __iomem *tegra210_timer_reg_base;
+static u32 usec_config;
+
+#define TIMER_PTV 0x0
+#define TIMER_PTV_EN BIT(31)
+#define TIMER_PTV_PER BIT(30)
+#define TIMER_PCR 0x4
+#define TIMER_PCR_INTR_CLR BIT(30)
+#define TIMERUS_CNTR_1US 0x10
+#define TIMERUS_USEC_CFG 0x14
+
+#define TIMER10_OFFSET 0x90
+
+#define TIMER_FOR_CPU(cpu) (TIMER10_OFFSET + (cpu) * 8)
+
+struct tegra210_clockevent {
+ struct clock_event_device evt;
+ char name[20];
+ void __iomem *reg_base;
+};
+#define to_tegra_cevt(p) (container_of(p, struct tegra210_clockevent, evt))
+
+static struct tegra210_clockevent __percpu *tegra210_evt;
+
+static int tegra210_timer_set_next_event(unsigned long cycles,
+ struct clock_event_device *evt)
+{
+ struct tegra210_clockevent *tevt;
+
+ tevt = to_tegra_cevt(evt);
+ writel(TIMER_PTV_EN |
+ ((cycles > 1) ? (cycles - 1) : 0), /* n+1 scheme */
+ tevt->reg_base + TIMER_PTV);
+
+ return 0;
+}
+
+static inline void timer_shutdown(struct tegra210_clockevent *tevt)
+{
+ writel(0, tevt->reg_base + TIMER_PTV);
+}
+
+static int tegra210_timer_shutdown(struct clock_event_device *evt)
+{
+ struct tegra210_clockevent *tevt;
+
+ tevt = to_tegra_cevt(evt);
+ timer_shutdown(tevt);
+
+ return 0;
+}
+
+static int tegra210_timer_set_periodic(struct clock_event_device *evt)
+{
+ struct tegra210_clockevent *tevt;
+
+ tevt = to_tegra_cevt(evt);
+ writel(TIMER_PTV_EN | TIMER_PTV_PER | ((tegra210_timer_freq / HZ) - 1),
+ tevt->reg_base + TIMER_PTV);
+
+ return 0;
+}
+
+static irqreturn_t tegra210_timer_isr(int irq, void *dev_id)
+{
+ struct tegra210_clockevent *tevt;
+
+ tevt = dev_id;
+ writel(TIMER_PCR_INTR_CLR, tevt->reg_base + TIMER_PCR);
+ tevt->evt.event_handler(&tevt->evt);
+
+ return IRQ_HANDLED;
+}
+
+static int tegra210_timer_setup(unsigned int cpu)
+{
+ struct tegra210_clockevent *tevt = per_cpu_ptr(tegra210_evt, cpu);
+
+ irq_force_affinity(tevt->evt.irq, cpumask_of(cpu));
+ enable_irq(tevt->evt.irq);
+
+ clockevents_config_and_register(&tevt->evt, tegra210_timer_freq,
+ 1, /* min */
+ 0x1fffffff); /* 29 bits */
+
+ return 0;
+}
+
+static int tegra210_timer_stop(unsigned int cpu)
+{
+ struct tegra210_clockevent *tevt = per_cpu_ptr(tegra210_evt, cpu);
+
+ tevt->evt.set_state_shutdown(&tevt->evt);
+ disable_irq_nosync(tevt->evt.irq);
+
+ return 0;
+}
+
+static int tegra_timer_suspend(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ void __iomem *reg_base = tegra210_timer_reg_base +
+ TIMER_FOR_CPU(cpu);
+ writel(TIMER_PCR_INTR_CLR, reg_base + TIMER_PCR);
+ }
+
+ return 0;
+}
+
+static void tegra_timer_resume(void)
+{
+ writel(usec_config, tegra210_timer_reg_base + TIMERUS_USEC_CFG);
+}
+
+static struct syscore_ops tegra_timer_syscore_ops = {
+ .suspend = tegra_timer_suspend,
+ .resume = tegra_timer_resume,
+};
+
+static int __init tegra210_timer_init(struct device_node *np)
+{
+ int cpu, ret;
+ struct tegra210_clockevent *tevt;
+ struct clk *clk;
+
+ tegra210_evt = alloc_percpu(struct tegra210_clockevent);
+ if (!tegra210_evt)
+ return -ENOMEM;
+
+ tegra210_timer_reg_base = of_iomap(np, 0);
+ if (!tegra210_timer_reg_base)
+ return -ENXIO;
+
+ clk = of_clk_get(np, 0);
+ if (IS_ERR(clk))
+ return -EINVAL;
+
+ clk_prepare_enable(clk);
+ tegra210_timer_freq = clk_get_rate(clk);
+
+ for_each_possible_cpu(cpu) {
+ tevt = per_cpu_ptr(tegra210_evt, cpu);
+ tevt->reg_base = tegra210_timer_reg_base + TIMER_FOR_CPU(cpu);
+ tevt->evt.irq = irq_of_parse_and_map(np, cpu);
+ if (!tevt->evt.irq) {
+ pr_err("%s: can't map IRQ for CPU%d\n",
+ __func__, cpu);
+ return -EINVAL;
+ }
+
+ snprintf(tevt->name, ARRAY_SIZE(tevt->name),
+ "tegra210_timer%d", cpu);
+ tevt->evt.name = tevt->name;
+ tevt->evt.cpumask = cpumask_of(cpu);
+ tevt->evt.set_next_event = tegra210_timer_set_next_event;
+ tevt->evt.set_state_shutdown = tegra210_timer_shutdown;
+ tevt->evt.set_state_periodic = tegra210_timer_set_periodic;
+ tevt->evt.set_state_oneshot = tegra210_timer_shutdown;
+ tevt->evt.tick_resume = tegra210_timer_shutdown;
+ tevt->evt.features = CLOCK_EVT_FEAT_PERIODIC |
+ CLOCK_EVT_FEAT_ONESHOT;
+ tevt->evt.rating = 460;
+
+ irq_set_status_flags(tevt->evt.irq, IRQ_NOAUTOEN);
+ ret = request_irq(tevt->evt.irq, tegra210_timer_isr,
+ IRQF_TIMER | IRQF_NOBALANCING,
+ tevt->name, tevt);
+ if (ret) {
+ pr_err("%s: cannot setup irq %d for CPU%d\n",
+ __func__, tevt->evt.irq, cpu);
+ return -EINVAL;
+ }
+ }
+
+ /*
+ * Configure microsecond timers to have 1MHz clock
+ * Config register is 0xqqww, where qq is "dividend", ww is "divisor"
+ * Uses n+1 scheme
+ */
+ switch (tegra210_timer_freq) {
+ case 12000000:
+ usec_config = 0x000b; /* (11+1)/(0+1) */
+ break;
+ case 12800000:
+ usec_config = 0x043f; /* (63+1)/(4+1) */
+ break;
+ case 13000000:
+ usec_config = 0x000c; /* (12+1)/(0+1) */
+ break;
+ case 16800000:
+ usec_config = 0x0453; /* (83+1)/(4+1) */
+ break;
+ case 19200000:
+ usec_config = 0x045f; /* (95+1)/(4+1) */
+ break;
+ case 26000000:
+ usec_config = 0x0019; /* (25+1)/(0+1) */
+ break;
+ case 38400000:
+ usec_config = 0x04bf; /* (191+1)/(4+1) */
+ break;
+ case 48000000:
+ usec_config = 0x002f; /* (47+1)/(0+1) */
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ writel(usec_config, tegra210_timer_reg_base + TIMERUS_USEC_CFG);
+
+ cpuhp_setup_state(CPUHP_AP_TEGRA_TIMER_STARTING,
+ "AP_TEGRA_TIMER_STARTING", tegra210_timer_setup,
+ tegra210_timer_stop);
+
+ register_syscore_ops(&tegra_timer_syscore_ops);
+
+ return 0;
+}

A couple comments with the above init function ...
1. Does not appear to clean-up after itself on error.

Ah, sorry, this is because any kinds of error which cause this driver fails to init the device will just be stuck after we enable CPU idle with C7 state due to armv8 timer is not able to wake it up. So I originally thought the clean-up was unnecessary. Anyway, will fix it.

2. What about the other TMRs? Do we have any use for these?


In this driver, only TMR10-TMR13 are used. We have another driver (tegra-wdt) which uses TMR5 for watchdog timer.

Thanks,
Joseph