Date:   Mon, 16 May 2022 11:33:42 -0500
From:   nick.hawkins@....com
To:     verdun@....com, nick.hawkins@....com, joel@....id.au,
        arnd@...db.de, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v8 4/8] clocksource/drivers/timer-gxp: Add HPE GXP Timer

From: Nick Hawkins <nick.hawkins@....com>

Add support for the HPE GXP SOC timer. The GXP supports several different
kinds of timers but for the purpose of this driver there is only support
for the General Timer. The timer has a 1us resolution and is 32 bits. The
timer also creates a child watchdog device as the register region is the
same.

Signed-off-by: Nick Hawkins <nick.hawkins@....com>

---
v8:
* No change
v7:
* Changed Kconfig conditional statements around COMPILE_TEST
* Added select TIMER_OF if OF
v6:
* Changed global variable name from local_gxp_timer to gxp_timer while
  removing the requirement for a local variable.
* Changed static void __iomem *system_clock to __ro_after_init from
  __read_mostly
* Changed subject to match the format from the logs
* Removed stray tab in the argument for gxp_time_set_next_event
* Made the commit description fit to 75 characters per line
* Created watchdog child dynamically with platform_device_alloc
* Fixed spacing in comments
v5:
* Corrected version log
* Removed uncessary include file
v4:
* Made watchdog a child of timer as they share the same register
  region
* Fixed watchdog init timeout call
* Fixed variable usage u32/u64
* Removed Read Once
* fixed error that should have been debug
v3:
* Put into proper patchset form
v2:
* No change
---
 drivers/clocksource/Kconfig     |   8 ++
 drivers/clocksource/Makefile    |   1 +
 drivers/clocksource/timer-gxp.c | 209 ++++++++++++++++++++++++++++++++
 3 files changed, 218 insertions(+)
 create mode 100644 drivers/clocksource/timer-gxp.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 1589ae7d5abb..be4dab9c1345 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -617,6 +617,14 @@ config CLKSRC_ST_LPC
 	  Enable this option to use the Low Power controller timer
 	  as clocksource.
 
+config GXP_TIMER
+	bool "GXP timer driver" if COMPILE_TEST && !ARCH_HPE
+	default ARCH_HPE
+	select TIMER_OF if OF
+	help
+	  Provides a driver for the timer control found on HPE
+	  GXP SOCs. This is required for all GXP SOCs.
+
 config RISCV_TIMER
 	bool "Timer for the RISC-V platform" if COMPILE_TEST
 	depends on GENERIC_SCHED_CLOCK && RISCV && RISCV_SBI
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 9c85ee2bb373..98017abf6c03 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -88,3 +88,4 @@ obj-$(CONFIG_GX6605S_TIMER)		+= timer-gx6605s.o
 obj-$(CONFIG_HYPERV_TIMER)		+= hyperv_timer.o
 obj-$(CONFIG_MICROCHIP_PIT64B)		+= timer-microchip-pit64b.o
 obj-$(CONFIG_MSC313E_TIMER)		+= timer-msc313e.o
+obj-$(CONFIG_GXP_TIMER)			+= timer-gxp.o
diff --git a/drivers/clocksource/timer-gxp.c b/drivers/clocksource/timer-gxp.c
new file mode 100644
index 000000000000..8b38b3212388
--- /dev/null
+++ b/drivers/clocksource/timer-gxp.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2022 Hewlett-Packard Enterprise Development Company, L.P. */
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/interrupt.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/sched_clock.h>
+
+#define TIMER0_FREQ	1000000
+#define GXP_TIMER_CNT_OFS 0x00
+#define GXP_TIMESTAMP_OFS 0x08
+#define GXP_TIMER_CTRL_OFS 0x14
+
+/* TCS Stands for Timer Control/Status: these are masks to be used in */
+/* the Timer Count Registers */
+#define MASK_TCS_ENABLE	0x01
+#define MASK_TCS_PERIOD	0x02
+#define MASK_TCS_RELOAD	0x04
+#define MASK_TCS_TC	0x80
+
+struct gxp_timer {
+	void __iomem *counter;
+	void __iomem *control;
+	struct clock_event_device evt;
+};
+
+static struct gxp_timer *gxp_timer;
+
+static void __iomem *system_clock __ro_after_init;
+
+static inline struct gxp_timer *to_gxp_timer(struct clock_event_device *evt_dev)
+{
+	return container_of(evt_dev, struct gxp_timer, evt);
+}
+
+static u64 notrace gxp_sched_read(void)
+{
+	return readl_relaxed(system_clock);
+}
+
+static int gxp_time_set_next_event(unsigned long event, struct clock_event_device *evt_dev)
+{
+	struct gxp_timer *timer = to_gxp_timer(evt_dev);
+
+	/* Stop counting and disable interrupt before updating */
+	writeb_relaxed(MASK_TCS_TC, timer->control);
+	writel_relaxed(event, timer->counter);
+	writeb_relaxed(MASK_TCS_TC | MASK_TCS_ENABLE, timer->control);
+
+	return 0;
+}
+
+static irqreturn_t gxp_timer_interrupt(int irq, void *dev_id)
+{
+	struct gxp_timer *timer = (struct gxp_timer *)dev_id;
+
+	if (!(readb_relaxed(timer->control) & MASK_TCS_TC))
+		return IRQ_NONE;
+
+	writeb_relaxed(MASK_TCS_TC, timer->control);
+
+	timer->evt.event_handler(&timer->evt);
+
+	return IRQ_HANDLED;
+}
+
+static int __init gxp_timer_init(struct device_node *node)
+{
+	void __iomem *base;
+	struct clk *clk;
+	u32 freq;
+	int ret, irq;
+
+	gxp_timer = kzalloc(sizeof(*gxp_timer), GFP_KERNEL);
+	if (!gxp_timer) {
+		ret = -ENOMEM;
+		pr_err("Can't allocate gxp_timer");
+		return ret;
+	}
+
+	clk = of_clk_get(node, 0);
+	if (IS_ERR(clk)) {
+		ret = (int)PTR_ERR(clk);
+		pr_err("%pOFn clock not found: %d\n", node, ret);
+		goto err_free;
+	}
+
+	ret = clk_prepare_enable(clk);
+	if (ret) {
+		pr_err("%pOFn clock enable failed: %d\n", node, ret);
+		goto err_clk_enable;
+	}
+
+	base = of_iomap(node, 0);
+	if (!base) {
+		ret = -ENXIO;
+		pr_err("Can't map timer base registers");
+		goto err_iomap;
+	}
+
+	/* Set the offsets to the clock register and timer registers */
+	gxp_timer->counter = base + GXP_TIMER_CNT_OFS;
+	gxp_timer->control = base + GXP_TIMER_CTRL_OFS;
+	system_clock = base + GXP_TIMESTAMP_OFS;
+
+	gxp_timer->evt.name = node->name;
+	gxp_timer->evt.rating = 300;
+	gxp_timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
+	gxp_timer->evt.set_next_event = gxp_time_set_next_event;
+	gxp_timer->evt.cpumask = cpumask_of(0);
+
+	irq = irq_of_parse_and_map(node, 0);
+	if (irq <= 0) {
+		ret = -EINVAL;
+		pr_err("GXP Timer Can't parse IRQ %d", irq);
+		goto err_exit;
+	}
+
+	freq = clk_get_rate(clk);
+
+	ret = clocksource_mmio_init(system_clock, node->name, freq,
+				    300, 32, clocksource_mmio_readl_up);
+	if (ret) {
+		pr_err("%pOFn init clocksource failed: %d", node, ret);
+		goto err_exit;
+	}
+
+	sched_clock_register(gxp_sched_read, 32, freq);
+
+	irq = irq_of_parse_and_map(node, 0);
+	if (irq <= 0) {
+		ret = -EINVAL;
+		pr_err("%pOFn Can't parse IRQ %d", node, irq);
+		goto err_exit;
+	}
+
+	clockevents_config_and_register(&gxp_timer->evt, TIMER0_FREQ,
+					0xf, 0xffffffff);
+
+	ret = request_irq(irq, gxp_timer_interrupt, IRQF_TIMER | IRQF_SHARED,
+			  node->name, gxp_timer);
+	if (ret) {
+		pr_err("%pOFn request_irq() failed: %d", node, ret);
+		goto err_exit;
+	}
+
+	pr_debug("gxp: system timer (irq = %d)\n", irq);
+	return 0;
+
+err_exit:
+	iounmap(base);
+err_iomap:
+	clk_disable_unprepare(clk);
+err_clk_enable:
+	clk_put(clk);
+err_free:
+	kfree(gxp_timer);
+	return ret;
+}
+
+/*
+ * This probe gets called after the timer is already up and running. This will create
+ * the watchdog device as a child since the registers are shared.
+ */
+
+static int gxp_timer_probe(struct platform_device *pdev)
+{
+	struct platform_device *gxp_watchdog_device;
+	struct device *dev = &pdev->dev;
+
+	if (!gxp_timer) {
+		pr_err("Gxp Timer not initialized, cannot create watchdog");
+		return -ENOMEM;
+	}
+
+	gxp_watchdog_device = platform_device_alloc("gxp-wdt", -1);
+	if (!gxp_watchdog_device) {
+		pr_err("Timer failed to allocate gxp-wdt");
+		return -ENOMEM;
+	}
+
+	/* Pass the base address (counter) as platform data and nothing else */
+	gxp_watchdog_device->dev.platform_data = gxp_timer->counter;
+	gxp_watchdog_device->dev.parent = dev;
+
+	return platform_device_add(gxp_watchdog_device);
+}
+
+static const struct of_device_id gxp_timer_of_match[] = {
+	{ .compatible = "hpe,gxp-timer", },
+	{},
+};
+
+static struct platform_driver gxp_timer_driver = {
+	.probe  = gxp_timer_probe,
+	.driver = {
+		.name = "gxp-timer",
+		.of_match_table = gxp_timer_of_match,
+		.suppress_bind_attrs = true,
+	},
+};
+
+builtin_platform_driver(gxp_timer_driver);
+
+TIMER_OF_DECLARE(gxp, "hpe,gxp-timer", gxp_timer_init);
-- 
2.17.1

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