[PATCH v3 2/7] clocksource: Add Tegra186 timers support

Thierry Reding
2020-04-03T20:22:38Z

Currently this only supports a single watchdog, which uses a timer in
the background for countdown. Eventually the timers could be used for
various time-keeping tasks, but by default the architected timer will
already provide that functionality.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v3:
- request IRQ at the end of ->probe() to avoid race condition
- only enable/disable watchdog when it's active
- use _relaxed variants of register accessors
- drop tegra186_timer.irq field

Changes in v2:
- add dependency on WATCHDOG && WATCHDOG_CORE
- expose TSC, OSC and USEC clocksources
- implement suspend/resume support
- make driver tristate

drivers/clocksource/Kconfig | 8 +
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-tegra186.c | 508 +++++++++++++++++++++++++++
3 files changed, 517 insertions(+)
create mode 100644 drivers/clocksource/timer-tegra186.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index f2142e6bbea3..385573c215d8 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -149,6 +149,14 @@ config TEGRA_TIMER
help
Enables support for the Tegra driver.

+config TEGRA186_TIMER
+ tristate "NVIDIA Tegra186 timer driver"
+ depends on ARCH_TEGRA || COMPILE_TEST
+ depends on WATCHDOG && WATCHDOG_CORE
+ help
+ Enables support for the timers and watchdogs found on NVIDIA
+ Tegra186 and later SoCs.
+
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 641ba5383ab5..ffa7950f4b7c 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -38,6 +38,7 @@ 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-tegra.o
+obj-$(CONFIG_TEGRA186_TIMER) += timer-tegra186.o
obj-$(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-tegra186.c b/drivers/clocksource/timer-tegra186.c
new file mode 100644
index 000000000000..4515517c87a5
--- /dev/null
+++ b/drivers/clocksource/timer-tegra186.c
@@ -0,0 +1,508 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2019-2020 NVIDIA Corporation. All rights reserved.
+ */
+
+#include <linux/clocksource.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/watchdog.h>
+
+/* shared registers */
+#define TKETSC0 0x000
+#define TKETSC1 0x004
+#define TKEUSEC 0x008
+#define TKEOSC 0x00c
+
+#define TKEIE(x) (0x100 + ((x) * 4))
+#define TKEIE_WDT_MASK(x, y) ((y) << (16 + 4 * (x)))
+
+/* timer registers */
+#define TMRCR 0x000
+#define TMRCR_ENABLE BIT(31)
+#define TMRCR_PERIODIC BIT(30)
+#define TMRCR_PTV(x) ((x) & 0x0fffffff)
+
+#define TMRSR 0x004
+#define TMRSR_INTR_CLR BIT(30)
+
+#define TMRCSSR 0x008
+#define TMRCSSR_SRC_USEC (0 << 0)
+
+/* watchdog registers */
+#define WDTCR 0x000
+#define WDTCR_SYSTEM_POR_RESET_ENABLE BIT(16)
+#define WDTCR_SYSTEM_DEBUG_RESET_ENABLE BIT(15)
+#define WDTCR_REMOTE_INT_ENABLE BIT(14)
+#define WDTCR_LOCAL_FIQ_ENABLE BIT(13)
+#define WDTCR_LOCAL_INT_ENABLE BIT(12)
+#define WDTCR_PERIOD_MASK (0xff << 4)
+#define WDTCR_PERIOD(x) (((x) & 0xff) << 4)
+#define WDTCR_TIMER_SOURCE_MASK 0xf
+#define WDTCR_TIMER_SOURCE(x) ((x) & 0xf)
+
+#define WDTCMDR 0x008
+#define WDTCMDR_DISABLE_COUNTER BIT(1)
+#define WDTCMDR_START_COUNTER BIT(0)
+
+#define WDTUR 0x00c
+#define WDTUR_UNLOCK_PATTERN 0x0000c45a
+
+struct tegra186_timer_soc {
+ unsigned int num_timers;
+ unsigned int num_wdts;
+};
+
+struct tegra186_tmr {
+ struct tegra186_timer *parent;
+ void __iomem *regs;
+ unsigned int index;
+ unsigned int hwirq;
+};
+
+struct tegra186_wdt {
+ struct watchdog_device base;
+
+ void __iomem *regs;
+ unsigned int index;
+ bool locked;
+
+ struct tegra186_tmr *tmr;
+};
+
+static inline struct tegra186_wdt *to_tegra186_wdt(struct watchdog_device *wdd)
+{
+ return container_of(wdd, struct tegra186_wdt, base);
+}
+
+struct tegra186_timer {
+ const struct tegra186_timer_soc *soc;
+ struct device *dev;
+ void __iomem *regs;
+
+ struct tegra186_wdt *wdt;
+ struct clocksource usec;
+ struct clocksource tsc;
+ struct clocksource osc;
+};
+
+static void tmr_writel(struct tegra186_tmr *tmr, u32 value, unsigned int offset)
+{
+ writel_relaxed(value, tmr->regs + offset);
+}
+
+static void wdt_writel(struct tegra186_wdt *wdt, u32 value, unsigned int offset)
+{
+ writel_relaxed(value, wdt->regs + offset);
+}
+
+static u32 wdt_readl(struct tegra186_wdt *wdt, unsigned int offset)
+{
+ return readl_relaxed(wdt->regs + offset);
+}
+
+static struct tegra186_tmr *tegra186_tmr_create(struct tegra186_timer *tegra,
+ unsigned int index)
+{
+ unsigned int offset = 0x10000 + index * 0x10000;
+ struct tegra186_tmr *tmr;
+
+ tmr = devm_kzalloc(tegra->dev, sizeof(*tmr), GFP_KERNEL);
+ if (!tmr)
+ return ERR_PTR(-ENOMEM);
+
+ tmr->parent = tegra;
+ tmr->regs = tegra->regs + offset;
+ tmr->index = index;
+ tmr->hwirq = 0;
+
+ return tmr;
+}
+
+static const struct watchdog_info tegra186_wdt_info = {
+ .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
+ .identity = "NVIDIA Tegra186 WDT",
+};
+
+static void tegra186_wdt_disable(struct tegra186_wdt *wdt)
+{
+ /* unlock and disable the watchdog */
+ wdt_writel(wdt, WDTUR_UNLOCK_PATTERN, WDTUR);
+ wdt_writel(wdt, WDTCMDR_DISABLE_COUNTER, WDTCMDR);
+
+ /* disable timer */
+ tmr_writel(wdt->tmr, 0, TMRCR);
+}
+
+static void tegra186_wdt_enable(struct tegra186_wdt *wdt)
+{
+ struct tegra186_timer *tegra = wdt->tmr->parent;
+ u32 value;
+
+ /* unmask hardware IRQ, this may have been lost across powergate */
+ value = TKEIE_WDT_MASK(wdt->index, 1);
+ writel(value, tegra->regs + TKEIE(wdt->tmr->hwirq));
+
+ /* clear interrupt */
+ tmr_writel(wdt->tmr, TMRSR_INTR_CLR, TMRSR);
+
+ /* select microsecond source */
+ tmr_writel(wdt->tmr, TMRCSSR_SRC_USEC, TMRCSSR);
+
+ /* configure timer (system reset happens on the fifth expiration) */
+ value = TMRCR_PTV(wdt->base.timeout * USEC_PER_SEC / 5) |
+ TMRCR_PERIODIC | TMRCR_ENABLE;
+ tmr_writel(wdt->tmr, value, TMRCR);
+
+ if (!wdt->locked) {
+ value = wdt_readl(wdt, WDTCR);
+
+ /* select the proper timer source */
+ value &= ~WDTCR_TIMER_SOURCE_MASK;
+ value |= WDTCR_TIMER_SOURCE(wdt->tmr->index);
+
+ /* single timer period since that's already configured */
+ value &= ~WDTCR_PERIOD_MASK;
+ value |= WDTCR_PERIOD(1);
+
+ /* enable local interrupt for WDT petting */
+ value |= WDTCR_LOCAL_INT_ENABLE;
+
+ /* enable local FIQ and remote interrupt for debug dump */
+ if (0)
+ value |= WDTCR_REMOTE_INT_ENABLE |
+ WDTCR_LOCAL_FIQ_ENABLE;
+
+ /* enable system debug reset (doesn't properly reboot) */
+ if (0)
+ value |= WDTCR_SYSTEM_DEBUG_RESET_ENABLE;
+
+ /* enable system POR reset */
+ value |= WDTCR_SYSTEM_POR_RESET_ENABLE;
+
+ wdt_writel(wdt, value, WDTCR);
+ }
+
+ wdt_writel(wdt, WDTCMDR_START_COUNTER, WDTCMDR);
+}
+
+static int tegra186_wdt_start(struct watchdog_device *wdd)
+{
+ struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
+
+ tegra186_wdt_enable(wdt);
+
+ return 0;
+}
+
+static int tegra186_wdt_stop(struct watchdog_device *wdd)
+{
+ struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
+
+ tegra186_wdt_disable(wdt);
+
+ return 0;
+}
+
+static int tegra186_wdt_ping(struct watchdog_device *wdd)
+{
+ struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
+
+ tegra186_wdt_disable(wdt);
+ tegra186_wdt_enable(wdt);
+
+ return 0;
+}
+
+static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
+ unsigned int timeout)
+{
+ struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
+
+ if (watchdog_active(&wdt->base))
+ tegra186_wdt_disable(wdt);
+
+ wdt->base.timeout = timeout;
+
+ if (watchdog_active(&wdt->base))
+ tegra186_wdt_enable(wdt);
+
+ return 0;
+}
+
+static const struct watchdog_ops tegra186_wdt_ops = {
+ .owner = THIS_MODULE,
+ .start = tegra186_wdt_start,
+ .stop = tegra186_wdt_stop,
+ .ping = tegra186_wdt_ping,
+ .set_timeout = tegra186_wdt_set_timeout,
+};
+
+static struct tegra186_wdt *tegra186_wdt_create(struct tegra186_timer *tegra,
+ unsigned int index)
+{
+ unsigned int offset = 0x10000, source;
+ struct tegra186_wdt *wdt;
+ u32 value;
+ int err;
+
+ offset += tegra->soc->num_timers * 0x10000 + index * 0x10000;
+
+ wdt = devm_kzalloc(tegra->dev, sizeof(*wdt), GFP_KERNEL);
+ if (!wdt)
+ return ERR_PTR(-ENOMEM);
+
+ wdt->regs = tegra->regs + offset;
+ wdt->index = index;
+
+ /* read the watchdog configuration since it might be locked down */
+ value = wdt_readl(wdt, WDTCR);
+
+ if (value & WDTCR_LOCAL_INT_ENABLE)
+ wdt->locked = true;
+
+ source = value & WDTCR_TIMER_SOURCE_MASK;
+
+ wdt->tmr = tegra186_tmr_create(tegra, source);
+ if (IS_ERR(wdt->tmr))
+ return ERR_CAST(wdt->tmr);
+
+ wdt->base.info = &tegra186_wdt_info;
+ wdt->base.ops = &tegra186_wdt_ops;
+ wdt->base.min_timeout = 1;
+ wdt->base.max_timeout = 255;
+ wdt->base.parent = tegra->dev;
+
+ err = watchdog_init_timeout(&wdt->base, 5, tegra->dev);
+ if (err < 0) {
+ dev_err(tegra->dev, "failed to initialize timeout: %d\n", err);
+ return ERR_PTR(err);
+ }
+
+ err = devm_watchdog_register_device(tegra->dev, &wdt->base);
+ if (err < 0) {
+ dev_err(tegra->dev, "failed to register WDT: %d\n", err);
+ return ERR_PTR(err);
+ }
+
+ return wdt;
+}
+
+static u64 tegra186_timer_tsc_read(struct clocksource *cs)
+{
+ struct tegra186_timer *tegra = container_of(cs, struct tegra186_timer,
+ tsc);
+ u32 hi, lo, ss;
+
+ hi = readl_relaxed(tegra->regs + TKETSC1);
+
+ /*
+ * The 56-bit value of the TSC is spread across two registers that are
+ * not synchronized. In order to read them atomically, ensure that the
+ * high 24 bits match before and after reading the low 32 bits.
+ */
+ do {
+ /* snapshot the high 24 bits */
+ ss = hi;
+
+ lo = readl_relaxed(tegra->regs + TKETSC0);
+ hi = readl_relaxed(tegra->regs + TKETSC1);
+ } while (hi != ss);
+
+ return (u64)hi << 32 | lo;
+}
+
+static int tegra186_timer_tsc_init(struct tegra186_timer *tegra)
+{
+ tegra->tsc.name = "tsc";
+ tegra->tsc.rating = 300;
+ tegra->tsc.read = tegra186_timer_tsc_read;
+ tegra->tsc.mask = CLOCKSOURCE_MASK(56);
+ tegra->tsc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+
+ return clocksource_register_hz(&tegra->tsc, 31250000);
+}
+
+static u64 tegra186_timer_osc_read(struct clocksource *cs)
+{
+ struct tegra186_timer *tegra = container_of(cs, struct tegra186_timer,
+ osc);
+
+ return readl_relaxed(tegra->regs + TKEOSC);
+}
+
+static int tegra186_timer_osc_init(struct tegra186_timer *tegra)
+{
+ tegra->osc.name = "osc";
+ tegra->osc.rating = 300;
+ tegra->osc.read = tegra186_timer_osc_read;
+ tegra->osc.mask = CLOCKSOURCE_MASK(32);
+ tegra->osc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+
+ return clocksource_register_hz(&tegra->osc, 38400000);
+}
+
+static u64 tegra186_timer_usec_read(struct clocksource *cs)
+{
+ struct tegra186_timer *tegra = container_of(cs, struct tegra186_timer,
+ usec);
+
+ return readl_relaxed(tegra->regs + TKEUSEC);
+}
+
+static int tegra186_timer_usec_init(struct tegra186_timer *tegra)
+{
+ tegra->usec.name = "usec";
+ tegra->usec.rating = 300;
+ tegra->usec.read = tegra186_timer_usec_read;
+ tegra->usec.mask = CLOCKSOURCE_MASK(32);
+ tegra->usec.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+
+ return clocksource_register_hz(&tegra->usec, USEC_PER_SEC);
+}
+
+static irqreturn_t tegra186_timer_irq(int irq, void *data)
+{
+ struct tegra186_timer *tegra = data;
+
+ if (watchdog_active(&tegra->wdt->base)) {
+ tegra186_wdt_disable(tegra->wdt);
+ tegra186_wdt_enable(tegra->wdt);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static int tegra186_timer_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct tegra186_timer *tegra;
+ unsigned int irq;
+ int err;
+
+ tegra = devm_kzalloc(dev, sizeof(*tegra), GFP_KERNEL);
+ if (!tegra)
+ return -ENOMEM;
+
+ tegra->soc = of_device_get_match_data(dev);
+ dev_set_drvdata(dev, tegra);
+ tegra->dev = dev;
+
+ tegra->regs = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(tegra->regs))
+ return PTR_ERR(tegra->regs);
+
+ err = platform_get_irq(pdev, 0);
+ if (err < 0)
+ return err;
+
+ irq = err;
+
+ /* create a watchdog using a preconfigured timer */
+ tegra->wdt = tegra186_wdt_create(tegra, 0);
+ if (IS_ERR(tegra->wdt)) {
+ err = PTR_ERR(tegra->wdt);
+ dev_err(dev, "failed to create WDT: %d\n", err);
+ return err;
+ }
+
+ err = tegra186_timer_tsc_init(tegra);
+ if (err < 0) {
+ dev_err(dev, "failed to register TSC counter: %d\n", err);
+ return err;
+ }
+
+ err = tegra186_timer_osc_init(tegra);
+ if (err < 0) {
+ dev_err(dev, "failed to register OSC counter: %d\n", err);
+ goto unregister_tsc;
+ }
+
+ err = tegra186_timer_usec_init(tegra);
+ if (err < 0) {
+ dev_err(dev, "failed to register USEC counter: %d\n", err);
+ goto unregister_osc;
+ }
+
+ err = devm_request_irq(dev, irq, tegra186_timer_irq, 0,
+ "tegra186-timer", tegra);
+ if (err < 0) {
+ dev_err(dev, "failed to request IRQ#%u: %d\n", irq, err);
+ goto unregister_usec;
+ }
+
+ return 0;
+
+unregister_usec:
+ clocksource_unregister(&tegra->usec);
+unregister_osc:
+ clocksource_unregister(&tegra->osc);
+unregister_tsc:
+ clocksource_unregister(&tegra->tsc);
+ return err;
+}
+
+static int tegra186_timer_remove(struct platform_device *pdev)
+{
+ struct tegra186_timer *tegra = platform_get_drvdata(pdev);
+
+ clocksource_unregister(&tegra->usec);
+ clocksource_unregister(&tegra->osc);
+ clocksource_unregister(&tegra->tsc);
+
+ return 0;
+}
+
+static int __maybe_unused tegra186_timer_suspend(struct device *dev)
+{
+ struct tegra186_timer *tegra = dev_get_drvdata(dev);
+
+ if (watchdog_active(&tegra->wdt->base))
+ tegra186_wdt_disable(tegra->wdt);
+
+ return 0;
+}
+
+static int __maybe_unused tegra186_timer_resume(struct device *dev)
+{
+ struct tegra186_timer *tegra = dev_get_drvdata(dev);
+
+ if (watchdog_active(&tegra->wdt->base))
+ tegra186_wdt_enable(tegra->wdt);
+
+ return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(tegra186_timer_pm_ops, tegra186_timer_suspend,
+ tegra186_timer_resume);
+
+static const struct tegra186_timer_soc tegra186_timer = {
+ .num_timers = 10,
+ .num_wdts = 3,
+};
+
+static const struct of_device_id tegra186_timer_of_match[] = {
+ { .compatible = "nvidia,tegra186-timer", .data = &tegra186_timer },
+ { }
+};
+MODULE_DEVICE_TABLE(of, tegra186_timer_of_match);
+
+static struct platform_driver tegra186_wdt_driver = {
+ .driver = {
+ .name = "tegra186-timer",
+ .pm = &tegra186_timer_pm_ops,
+ .of_match_table = tegra186_timer_of_match,
+ },
+ .probe = tegra186_timer_probe,
+ .remove = tegra186_timer_remove,
+};
+module_platform_driver(tegra186_wdt_driver);
+
+MODULE_AUTHOR("Thierry Reding <treding@nvidia.com>");
+MODULE_DESCRIPTION("NVIDIA Tegra186 timers driver");
+MODULE_LICENSE("GPL v2");
--
2.24.1