[PATCH V2 1/6] dt-bindings: timer: add Tegra210 timer

[PATCH V2 1/6] dt-bindings: timer: add Tegra210 timer

[Joseph Lo]

The Tegra210 timer provides fourteen 29-bit timer counters and one 32-bit
timestamp counter. The TMRs run at either a fixed 1 MHz clock rate derived
from the oscillator clock (TMR0-TMR9) or directly at the oscillator clock
(TMR10-TMR13). Each TMR can be programmed to generate one-shot periodic,
or watchdog interrupts.

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: devicetree@vger.kernel.org
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>
---
v2:
 * list all the interrupts that are supported by tegra210 timers block
 * add RB tag from Rob.
---
 .../bindings/timer/nvidia,tegra210-timer.txt  | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/nvidia,tegra210-timer.txt

diff --git a/Documentation/devicetree/bindings/timer/nvidia,tegra210-timer.txt b/Documentation/devicetree/bindings/timer/nvidia,tegra210-timer.txt
new file mode 100644
index 000000000000..032cda96fe0d
--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/nvidia,tegra210-timer.txt
@@ -0,0 +1,36 @@
+NVIDIA Tegra210 timer
+
+The Tegra210 timer provides fourteen 29-bit timer counters and one 32-bit
+timestamp counter. The TMRs run at either a fixed 1 MHz clock rate derived
+from the oscillator clock (TMR0-TMR9) or directly at the oscillator clock
+(TMR10-TMR13). Each TMR can be programmed to generate one-shot, periodic,
+or watchdog interrupts.
+
+Required properties:
+- compatible : "nvidia,tegra210-timer".
+- reg : Specifies base physical address and size of the registers.
+- interrupts : A list of 14 interrupts; one per each timer channels 0 through
+  13.
+- clocks : Must contain one entry, for the module clock.
+  See ../clocks/clock-bindings.txt for details.
+
+timer@60005000 {
+	compatible = "nvidia,tegra210-timer";
+	reg = <0x0 0x60005000 0x0 0x400>;
+	interrupts = <GIC_SPI 156 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 1 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 41 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 42 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 121 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 152 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 153 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 154 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 155 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 176 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 177 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 178 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 179 IRQ_TYPE_LEVEL_HIGH>;
+	clocks = <&tegra_car TEGRA210_CLK_TIMER>;
+	clock-names = "timer";
+};
-- 
2.20.1

[PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Joseph Lo]

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@nvidia.com>

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Joseph Lo <josephl@nvidia.com>
---
v2:
 * add error clean-up code
---
 drivers/clocksource/Kconfig          |   3 +
 drivers/clocksource/Makefile         |   1 +
 drivers/clocksource/timer-tegra210.c | 268 +++++++++++++++++++++++++++
 include/linux/cpuhotplug.h           |   1 +
 4 files changed, 273 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..477b164e540b
--- /dev/null
+++ b/drivers/clocksource/timer-tegra210.c
@@ -0,0 +1,268 @@
+// 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 TIMER10_IRQ_IDX		10
+
+#define TIMER_FOR_CPU(cpu) (TIMER10_OFFSET + (cpu) * 8)
+#define IRQ_IDX_FOR_CPU(cpu)	(TIMER10_IRQ_IDX + cpu)
+
+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 = 0;
+	struct tegra210_clockevent *tevt;
+	struct clk *clk;
+
+	tegra210_evt = alloc_percpu(struct tegra210_clockevent);
+	if (!tegra210_evt) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	tegra210_timer_reg_base = of_iomap(np, 0);
+	if (!tegra210_timer_reg_base) {
+		ret = -ENXIO;
+		goto out_free_mem;
+	}
+
+	clk = of_clk_get(np, 0);
+	if (IS_ERR(clk)) {
+		ret = -EINVAL;
+		goto out_iounmap;
+	}
+
+	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, IRQ_IDX_FOR_CPU(cpu));
+		if (!tevt->evt.irq) {
+			pr_err("%s: can't map IRQ for CPU%d\n",
+			       __func__, cpu);
+			ret = -EINVAL;
+			goto out_clk;
+		}
+
+		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);
+			ret = -EINVAL;
+			goto out_irq;
+		}
+	}
+
+	/*
+	 * 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:
+		ret = -EINVAL;
+		goto out_irq;
+	}
+
+	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 ret;
+
+out_irq:
+	for_each_possible_cpu(cpu) {
+		tevt = per_cpu_ptr(tegra210_evt, cpu);
+		if (tevt->evt.irq) {
+			free_irq(tevt->evt.irq, tevt);
+			irq_dispose_mapping(tevt->evt.irq);
+		}
+	}
+out_clk:
+	clk_put(clk);
+out_iounmap:
+	iounmap(tegra210_timer_reg_base);
+out_free_mem:
+	free_percpu(tegra210_evt);
+out:
+	return ret;
+}
+
+TIMER_OF_DECLARE(tegra210_timer, "nvidia,tegra210-timer", tegra210_timer_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index fd586d0301e7..e78281d07b70 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -121,6 +121,7 @@ enum cpuhp_state {
 	CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
 	CPUHP_AP_ARM_TWD_STARTING,
 	CPUHP_AP_QCOM_TIMER_STARTING,
+	CPUHP_AP_TEGRA_TIMER_STARTING,
 	CPUHP_AP_ARMADA_TIMER_STARTING,
 	CPUHP_AP_MARCO_TIMER_STARTING,
 	CPUHP_AP_MIPS_GIC_TIMER_STARTING,
-- 
2.20.1

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Daniel Lezcano]

On 28/01/2019 10:18, 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@nvidia.com>
> 
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Joseph Lo <josephl@nvidia.com>
> ---
> v2:
>  * add error clean-up code
> ---
>  drivers/clocksource/Kconfig          |   3 +
>  drivers/clocksource/Makefile         |   1 +
>  drivers/clocksource/timer-tegra210.c | 268 +++++++++++++++++++++++++++
>  include/linux/cpuhotplug.h           |   1 +
>  4 files changed, 273 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
> +

Please make the option consistent with the option below (VT8500_TIMER or
similar).

>  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..477b164e540b
> --- /dev/null
> +++ b/drivers/clocksource/timer-tegra210.c
> @@ -0,0 +1,268 @@
> +// 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 TIMER10_IRQ_IDX		10
> +
> +#define TIMER_FOR_CPU(cpu) (TIMER10_OFFSET + (cpu) * 8)
> +#define IRQ_IDX_FOR_CPU(cpu)	(TIMER10_IRQ_IDX + cpu)
> +
> +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 = 0;
> +	struct tegra210_clockevent *tevt;
> +	struct clk *clk;
> +
> +	tegra210_evt = alloc_percpu(struct tegra210_clockevent);
> +	if (!tegra210_evt) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	tegra210_timer_reg_base = of_iomap(np, 0);
> +	if (!tegra210_timer_reg_base) {
> +		ret = -ENXIO;
> +		goto out_free_mem;
> +	}
> +
> +	clk = of_clk_get(np, 0);
> +	if (IS_ERR(clk)) {
> +		ret = -EINVAL;
> +		goto out_iounmap;
> +	}
> +
> +	clk_prepare_enable(clk);
> +	tegra210_timer_freq = clk_get_rate(clk);


Use the timer-of API for each CPU.

> +	for_each_possible_cpu(cpu) {


No cpu loop for the initialization, use the tegra210_timer_setup for
this (cf. armada 370 timer).

> +		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, IRQ_IDX_FOR_CPU(cpu));
> +		if (!tevt->evt.irq) {
> +			pr_err("%s: can't map IRQ for CPU%d\n",
> +			       __func__, cpu);
> +			ret = -EINVAL;
> +			goto out_clk;
> +		}
> +
> +		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);

Why do you need to prevent the interrupt to be enabled ? If the timer is
stopped and cleared, no spurious interrupt will occur no ?

> +		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);
> +			ret = -EINVAL;
> +			goto out_irq;
> +		}
> +	}
> +
> +	/*
> +	 * Configure microsecond timers to have 1MHz clock
> +	 * Config register is 0xqqww, where qq is "dividend", ww is "divisor"

Did you mean 0xwwqq ?

> +	 * 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:
> +		ret = -EINVAL;
> +		goto out_irq;
> +	}
> +
> +	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 ret;
> +
> +out_irq:
> +	for_each_possible_cpu(cpu) {
> +		tevt = per_cpu_ptr(tegra210_evt, cpu);
> +		if (tevt->evt.irq) {
> +			free_irq(tevt->evt.irq, tevt);
> +			irq_dispose_mapping(tevt->evt.irq);
> +		}
> +	}
> +out_clk:
> +	clk_put(clk);
> +out_iounmap:
> +	iounmap(tegra210_timer_reg_base);
> +out_free_mem:
> +	free_percpu(tegra210_evt);
> +out:
> +	return ret;
> +}
> +
> +TIMER_OF_DECLARE(tegra210_timer, "nvidia,tegra210-timer", tegra210_timer_init);
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index fd586d0301e7..e78281d07b70 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -121,6 +121,7 @@ enum cpuhp_state {
>  	CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
>  	CPUHP_AP_ARM_TWD_STARTING,
>  	CPUHP_AP_QCOM_TIMER_STARTING,
> +	CPUHP_AP_TEGRA_TIMER_STARTING,
>  	CPUHP_AP_ARMADA_TIMER_STARTING,
>  	CPUHP_AP_MARCO_TIMER_STARTING,
>  	CPUHP_AP_MIPS_GIC_TIMER_STARTING,
> 


-- 
 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Thierry Reding]

[-- Attachment #1: Type: text/plain, Size: 5452 bytes --]

On Mon, Jan 28, 2019 at 05:18:11PM +0800, 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@nvidia.com>
> 
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Joseph Lo <josephl@nvidia.com>
> ---
> v2:
>  * add error clean-up code
> ---
>  drivers/clocksource/Kconfig          |   3 +
>  drivers/clocksource/Makefile         |   1 +
>  drivers/clocksource/timer-tegra210.c | 268 +++++++++++++++++++++++++++
>  include/linux/cpuhotplug.h           |   1 +
>  4 files changed, 273 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..477b164e540b
> --- /dev/null
> +++ b/drivers/clocksource/timer-tegra210.c
> @@ -0,0 +1,268 @@
> +// 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 TIMER10_IRQ_IDX		10
> +
> +#define TIMER_FOR_CPU(cpu) (TIMER10_OFFSET + (cpu) * 8)
> +#define IRQ_IDX_FOR_CPU(cpu)	(TIMER10_IRQ_IDX + cpu)
> +
> +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;
> +}

Up to here this is a duplicate of timer-tegra20.c. And a lot of
tegra210_timer_init() is the same as tegra20_timer_init() as well. Can't
we unify the two drivers instead?

The power cycle restrictions of the architected timer, do they not apply
to chips earlier than Tegra210 either? So don't we need all of these
additional features on the timer-tegra20.c driver as well? If so that
would increase the code duplication even more. I think we should avoid
that, unless there are any strong arguments that would justify it.

Thierry

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Joseph Lo]

Hi Daniel,

Thanks for your review.

On 1/28/19 9:00 PM, Daniel Lezcano wrote:
> On 28/01/2019 10:18, 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@nvidia.com>
>>
>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Joseph Lo <josephl@nvidia.com>
>> ---
>> v2:
>>   * add error clean-up code
>> ---
>>   drivers/clocksource/Kconfig          |   3 +
>>   drivers/clocksource/Makefile         |   1 +
>>   drivers/clocksource/timer-tegra210.c | 268 +++++++++++++++++++++++++++
>>   include/linux/cpuhotplug.h           |   1 +
>>   4 files changed, 273 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
>> +
> 
> Please make the option consistent with the option below (VT8500_TIMER or
> similar).

Okay, will check.

> 
>>   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..477b164e540b
>> --- /dev/null
>> +++ b/drivers/clocksource/timer-tegra210.c
>> @@ -0,0 +1,268 @@
>> +// 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 TIMER10_IRQ_IDX		10
>> +
>> +#define TIMER_FOR_CPU(cpu) (TIMER10_OFFSET + (cpu) * 8)
>> +#define IRQ_IDX_FOR_CPU(cpu)	(TIMER10_IRQ_IDX + cpu)
>> +
>> +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 = 0;
>> +	struct tegra210_clockevent *tevt;
>> +	struct clk *clk;
>> +
>> +	tegra210_evt = alloc_percpu(struct tegra210_clockevent);
>> +	if (!tegra210_evt) {
>> +		ret = -ENOMEM;
>> +		goto out;
>> +	}
>> +
>> +	tegra210_timer_reg_base = of_iomap(np, 0);
>> +	if (!tegra210_timer_reg_base) {
>> +		ret = -ENXIO;
>> +		goto out_free_mem;
>> +	}
>> +
>> +	clk = of_clk_get(np, 0);
>> +	if (IS_ERR(clk)) {
>> +		ret = -EINVAL;
>> +		goto out_iounmap;
>> +	}
>> +
>> +	clk_prepare_enable(clk);
>> +	tegra210_timer_freq = clk_get_rate(clk);
> 
> 
> Use the timer-of API for each CPU.

Okay, I'll try to apply that for TIMER_OF_BASE and TIMER_OF_CLOCK. But 
the TIMER_OF_IRQ, as you see below, it didn't have the ability to handle 
the case that multiple CPUs with different timer IRQ lines. Which means 
it's not PPI.

> 
>> +	for_each_possible_cpu(cpu) {
> 
> 
> No cpu loop for the initialization, use the tegra210_timer_setup for
> this (cf. armada 370 timer).

As mentioned above, I may still need this for IRQs initialization for 
each CPU cores. Something like the IRQ init code in "exnos_mct.c".

> 
>> +		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, IRQ_IDX_FOR_CPU(cpu));
>> +		if (!tevt->evt.irq) {
>> +			pr_err("%s: can't map IRQ for CPU%d\n",
>> +			       __func__, cpu);
>> +			ret = -EINVAL;
>> +			goto out_clk;
>> +		}
>> +
>> +		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);
> 
> Why do you need to prevent the interrupt to be enabled ? If the timer is
> stopped and cleared, no spurious interrupt will occur no ?

This is to prevent the IRQ will been enabled twice in the timer_setup 
API with CPU hotplug event triggered. So we only enable the IRQ once the 
CPU is online.

> 
>> +		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);
>> +			ret = -EINVAL;
>> +			goto out_irq;
>> +		}
>> +	}
>> +
>> +	/*
>> +	 * Configure microsecond timers to have 1MHz clock
>> +	 * Config register is 0xqqww, where qq is "dividend", ww is "divisor"
> 
> Did you mean 0xwwqq ?

Ah, because it's microsecond timer, that means the fraction of 1 
microsecond each clk represents. For ex, if the clk is running at 12MHz, 
then each clk represents 1/12 of a microsecond.

Thanks,
Joseph

> 
>> +	 * 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:
>> +		ret = -EINVAL;
>> +		goto out_irq;
>> +	}
>> +
>> +	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 ret;
>> +
>> +out_irq:
>> +	for_each_possible_cpu(cpu) {
>> +		tevt = per_cpu_ptr(tegra210_evt, cpu);
>> +		if (tevt->evt.irq) {
>> +			free_irq(tevt->evt.irq, tevt);
>> +			irq_dispose_mapping(tevt->evt.irq);
>> +		}
>> +	}
>> +out_clk:
>> +	clk_put(clk);
>> +out_iounmap:
>> +	iounmap(tegra210_timer_reg_base);
>> +out_free_mem:
>> +	free_percpu(tegra210_evt);
>> +out:
>> +	return ret;
>> +}
>> +
>> +TIMER_OF_DECLARE(tegra210_timer, "nvidia,tegra210-timer", tegra210_timer_init);
>> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
>> index fd586d0301e7..e78281d07b70 100644
>> --- a/include/linux/cpuhotplug.h
>> +++ b/include/linux/cpuhotplug.h
>> @@ -121,6 +121,7 @@ enum cpuhp_state {
>>   	CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
>>   	CPUHP_AP_ARM_TWD_STARTING,
>>   	CPUHP_AP_QCOM_TIMER_STARTING,
>> +	CPUHP_AP_TEGRA_TIMER_STARTING,
>>   	CPUHP_AP_ARMADA_TIMER_STARTING,
>>   	CPUHP_AP_MARCO_TIMER_STARTING,
>>   	CPUHP_AP_MIPS_GIC_TIMER_STARTING,
>>
> 
> 

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Joseph Lo]

On 1/28/19 11:09 PM, Thierry Reding wrote:
> On Mon, Jan 28, 2019 at 05:18:11PM +0800, 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@nvidia.com>
>>
>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Joseph Lo <josephl@nvidia.com>
>> ---
>> v2:
>>   * add error clean-up code
>> ---
>>   drivers/clocksource/Kconfig          |   3 +
>>   drivers/clocksource/Makefile         |   1 +
>>   drivers/clocksource/timer-tegra210.c | 268 +++++++++++++++++++++++++++
>>   include/linux/cpuhotplug.h           |   1 +
>>   4 files changed, 273 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..477b164e540b
>> --- /dev/null
>> +++ b/drivers/clocksource/timer-tegra210.c
>> @@ -0,0 +1,268 @@
>> +// 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 TIMER10_IRQ_IDX		10
>> +
>> +#define TIMER_FOR_CPU(cpu) (TIMER10_OFFSET + (cpu) * 8)
>> +#define IRQ_IDX_FOR_CPU(cpu)	(TIMER10_IRQ_IDX + cpu)
>> +
>> +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;
>> +}
> 
> Up to here this is a duplicate of timer-tegra20.c. And a lot of
> tegra210_timer_init() is the same as tegra20_timer_init() as well. Can't
> we unify the two drivers instead?

I still prefer to remove the timer-tegra20 driver, because it didn't 
been used for Tegra 32 bit chips for quite a long time. So currently it 
just compiles OK, I also doubt the functionality still can achieve the 
same what I want to do for Tegra210.

My personal opinion is to remove the old and unused driver and enhance 
the new one.

> 
> The power cycle restrictions of the architected timer, do they not apply
> to chips earlier than Tegra210 either? So don't we need all of these
> additional features on the timer-tegra20.c driver as well? If so that
> would increase the code duplication even more. I think we should avoid
> that, unless there are any strong arguments that would justify it.
> 

As far as I know, this was a issue on some specific version of Cortex-a57.
For timer-tegra20, which was designed for the very early stage that TWD 
driver was not ready yet for Tegra 32 bit chips (Tegra20/30). Currently, 
it has been replaced by ARM TWD and V7 timer driver. It didn't been used 
and maintained for quite a long time.

BTW, we had very similar issue with idle power-down state with Tegra 
32bit chips. But it's related to GIC not timer. See below two changes 
for reference.

For Tegra20,
d4b92fb2535a ARM: tegra: add pending SGI checking API

For Tegra114/124,
7e8b15dbc392 ARM: tegra114: Reprogram GIC CPU interface to bypass IRQ on 
CPU PM entry

Thanks,
Joseph

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Peter De Schrijver]

On Mon, Jan 28, 2019 at 04:09:08PM +0100, Thierry Reding wrote:

...

> 
> Up to here this is a duplicate of timer-tegra20.c. And a lot of
> tegra210_timer_init() is the same as tegra20_timer_init() as well. Can't
> we unify the two drivers instead?
> 
> The power cycle restrictions of the architected timer, do they not apply
> to chips earlier than Tegra210 either? So don't we need all of these
> additional features on the timer-tegra20.c driver as well? If so that

No. Chips prior to Tegra114 do not have an arch timer and the arch timer
does work correctly on Cortex-A15 so Tegra114 and Tegra124 can use it.
It's broken on Cortex-A57 though, so we can't use it as a wakeup source
on Tegra210.

Peter.

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Jon Hunter]

On 29/01/2019 03:35, Joseph Lo wrote:
> On 1/28/19 11:09 PM, Thierry Reding wrote:
>> On Mon, Jan 28, 2019 at 05:18:11PM +0800, 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@nvidia.com>
>>>
>>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: linux-kernel@vger.kernel.org
>>> Signed-off-by: Joseph Lo <josephl@nvidia.com>
>>> ---
>>> v2:
>>>   * add error clean-up code
>>> ---
>>>   drivers/clocksource/Kconfig          |   3 +
>>>   drivers/clocksource/Makefile         |   1 +
>>>   drivers/clocksource/timer-tegra210.c | 268 +++++++++++++++++++++++++++
>>>   include/linux/cpuhotplug.h           |   1 +
>>>   4 files changed, 273 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..477b164e540b
>>> --- /dev/null
>>> +++ b/drivers/clocksource/timer-tegra210.c
>>> @@ -0,0 +1,268 @@
>>> +// 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 TIMER10_IRQ_IDX        10
>>> +
>>> +#define TIMER_FOR_CPU(cpu) (TIMER10_OFFSET + (cpu) * 8)
>>> +#define IRQ_IDX_FOR_CPU(cpu)    (TIMER10_IRQ_IDX + cpu)
>>> +
>>> +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;
>>> +}
>>
>> Up to here this is a duplicate of timer-tegra20.c. And a lot of
>> tegra210_timer_init() is the same as tegra20_timer_init() as well. Can't
>> we unify the two drivers instead?
> 
> I still prefer to remove the timer-tegra20 driver, because it didn't
> been used for Tegra 32 bit chips for quite a long time. So currently it
> just compiles OK, I also doubt the functionality still can achieve the
> same what I want to do for Tegra210.
> 
> My personal opinion is to remove the old and unused driver and enhance
> the new one.

Although it may not be used it is still a valid clocksource and could be
used. Our preference is to keeping the existing timer driver and enhance
to support T210 (unless there is some fundamental issue that would
prevent this that I am overlooking).

Cheers
Jon

-- 
nvpublic

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Thierry Reding]

[-- Attachment #1: Type: text/plain, Size: 1000 bytes --]

On Tue, Jan 29, 2019 at 10:41:55AM +0200, Peter De Schrijver wrote:
> On Mon, Jan 28, 2019 at 04:09:08PM +0100, Thierry Reding wrote:
> 
> ...
> 
> > 
> > Up to here this is a duplicate of timer-tegra20.c. And a lot of
> > tegra210_timer_init() is the same as tegra20_timer_init() as well. Can't
> > we unify the two drivers instead?
> > 
> > The power cycle restrictions of the architected timer, do they not apply
> > to chips earlier than Tegra210 either? So don't we need all of these
> > additional features on the timer-tegra20.c driver as well? If so that
> 
> No. Chips prior to Tegra114 do not have an arch timer and the arch timer
> does work correctly on Cortex-A15 so Tegra114 and Tegra124 can use it.
> It's broken on Cortex-A57 though, so we can't use it as a wakeup source
> on Tegra210.

If chips prior to Tegra114 don't have an architected timer, then we
can't remove the timer-tegra20 driver, because we still need it on
Tegra20 and Tegra30, right?

Thierry

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Joseph Lo]

On 1/29/19 6:29 PM, Thierry Reding wrote:
> On Tue, Jan 29, 2019 at 10:41:55AM +0200, Peter De Schrijver wrote:
>> On Mon, Jan 28, 2019 at 04:09:08PM +0100, Thierry Reding wrote:
>>
>> ...
>>
>>>
>>> Up to here this is a duplicate of timer-tegra20.c. And a lot of
>>> tegra210_timer_init() is the same as tegra20_timer_init() as well. Can't
>>> we unify the two drivers instead?
>>>
>>> The power cycle restrictions of the architected timer, do they not apply
>>> to chips earlier than Tegra210 either? So don't we need all of these
>>> additional features on the timer-tegra20.c driver as well? If so that
>>
>> No. Chips prior to Tegra114 do not have an arch timer and the arch timer
>> does work correctly on Cortex-A15 so Tegra114 and Tegra124 can use it.
>> It's broken on Cortex-A57 though, so we can't use it as a wakeup source
>> on Tegra210.
> 
> If chips prior to Tegra114 don't have an architected timer, then we
> can't remove the timer-tegra20 driver, because we still need it on
> Tegra20 and Tegra30, right?
> 

For Tegra20/30, it's Cortext-A9 with TWD timer. (arch/arm/kernel/smp_twd.c)

Originally, I thought the functionality of timer-tegra20 would be fully 
replaced by TWD timer driver. But from the log in the kernelci test 
farm[1][2], it looks to me the timer-tegra20 driver still works as 
clocksource driver for Tegra20/30. I cannot confirm if the clock event 
device has been replaced by TWD timer in the log. It could be replaced 
in the background. And by looking into the driver, it should be.

Compare to the log of Tegra124[3], it has been fully replaced by arch 
timer driver.

Note, "timer_us" is the name of Tegra20 timer.
[1]: 
https://storage.kernelci.org/mainline/master/v5.0-rc4-1-g4aa9fc2a435a/arm/tegra_defconfig/lab-baylibre-seattle/boot-tegra30-beaver.html
[2]: 
https://storage.kernelci.org/stable-rc/linux-4.9.y/v4.9.153-43-g6674590d15d2/arm/tegra_defconfig/lab-baylibre-seattle/boot-tegra20-iris-512.html
[3]: 
https://storage.kernelci.org/lsk/linux-linaro-lsk-v4.9/lsk-v4.9-18.09-1494-gde3059d32f93/arm/tegra_defconfig/lab-collabora/boot-tegra124-nyan-big.html

Thanks,
Joseph

Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver

[Peter De Schrijver]

On Wed, Jan 30, 2019 at 10:40:06AM +0800, Joseph Lo wrote:
> On 1/29/19 6:29 PM, Thierry Reding wrote:
> > On Tue, Jan 29, 2019 at 10:41:55AM +0200, Peter De Schrijver wrote:
> > > On Mon, Jan 28, 2019 at 04:09:08PM +0100, Thierry Reding wrote:
> > > 
> > > ...
> > > 
> > > > 
> > > > Up to here this is a duplicate of timer-tegra20.c. And a lot of
> > > > tegra210_timer_init() is the same as tegra20_timer_init() as well. Can't
> > > > we unify the two drivers instead?
> > > > 
> > > > The power cycle restrictions of the architected timer, do they not apply
> > > > to chips earlier than Tegra210 either? So don't we need all of these
> > > > additional features on the timer-tegra20.c driver as well? If so that
> > > 
> > > No. Chips prior to Tegra114 do not have an arch timer and the arch timer
> > > does work correctly on Cortex-A15 so Tegra114 and Tegra124 can use it.
> > > It's broken on Cortex-A57 though, so we can't use it as a wakeup source
> > > on Tegra210.
> > 
> > If chips prior to Tegra114 don't have an architected timer, then we
> > can't remove the timer-tegra20 driver, because we still need it on
> > Tegra20 and Tegra30, right?
> > 
> 
> For Tegra20/30, it's Cortext-A9 with TWD timer. (arch/arm/kernel/smp_twd.c)
> 
> Originally, I thought the functionality of timer-tegra20 would be fully
> replaced by TWD timer driver. But from the log in the kernelci test
> farm[1][2], it looks to me the timer-tegra20 driver still works as
> clocksource driver for Tegra20/30. I cannot confirm if the clock event
> device has been replaced by TWD timer in the log. It could be replaced in
> the background. And by looking into the driver, it should be.

The TWD timer runs from the CPU clock so its frequency changes with
CPU DVFS. That makes it difficult to use.

Peter.