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Subject[PATCH v2 2/2] clocksource: Add driver for the Ingenic JZ47xx OST
Date
From: Maarten ter Huurne <maarten@treewalker.org>

OST is the OS Timer, a 64-bit timer/counter with buffered reading.

SoCs before the JZ4770 had (if any) a 32-bit OST; the JZ4770 and
JZ4780 have a 64-bit OST.

This driver will register both a clocksource and a sched_clock to the
system.

Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
---

Notes:
v2: local_irq_save/restore were moved within sched_clock_register

drivers/clocksource/Kconfig | 8 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/ingenic-ost.c | 218 ++++++++++++++++++++++++++++++
3 files changed, 227 insertions(+)
create mode 100644 drivers/clocksource/ingenic-ost.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 5fdd76cb1768..5be2f876f64f 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -697,4 +697,12 @@ config INGENIC_TIMER
help
Support for the timer/counter unit of the Ingenic JZ SoCs.

+config INGENIC_OST
+ bool "Ingenic JZ47xx Operating System Timer"
+ depends on MIPS || COMPILE_TEST
+ depends on COMMON_CLK
+ select MFD_SYSCON
+ help
+ Support for the OS Timer of the Ingenic JZ4770 or similar SoC.
+
endmenu
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 4dfe4225ece7..6bc97a6fd229 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -80,6 +80,7 @@ obj-$(CONFIG_ASM9260_TIMER) += asm9260_timer.o
obj-$(CONFIG_H8300_TMR8) += h8300_timer8.o
obj-$(CONFIG_H8300_TMR16) += h8300_timer16.o
obj-$(CONFIG_H8300_TPU) += h8300_tpu.o
+obj-$(CONFIG_INGENIC_OST) += ingenic-ost.o
obj-$(CONFIG_INGENIC_TIMER) += ingenic-timer.o
obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
obj-$(CONFIG_X86_NUMACHIP) += numachip.o
diff --git a/drivers/clocksource/ingenic-ost.c b/drivers/clocksource/ingenic-ost.c
new file mode 100644
index 000000000000..dbb1d9634771
--- /dev/null
+++ b/drivers/clocksource/ingenic-ost.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * JZ47xx SoCs TCU Operating System Timer driver
+ *
+ * Copyright (C) 2016 Maarten ter Huurne <maarten@treewalker.org>
+ * Copyright (C) 2018 Paul Cercueil <paul@crapouillou.net>
+ */
+
+#include <linux/clk.h>
+#include <linux/clocksource.h>
+#include <linux/mfd/ingenic-tcu.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/regmap.h>
+#include <linux/sched_clock.h>
+
+#define TCU_OST_TCSR_MASK 0xffc0
+#define TCU_OST_TCSR_CNT_MD BIT(15)
+
+#define TCU_OST_CHANNEL 15
+
+struct ingenic_ost_soc_info {
+ bool is64bit;
+};
+
+struct ingenic_ost {
+ struct regmap *map;
+ struct clk *clk;
+
+ struct clocksource cs;
+};
+
+static struct ingenic_ost *ingenic_ost;
+
+static u64 notrace ingenic_ost_read_cntl(void)
+{
+ u32 val;
+
+ regmap_read(ingenic_ost->map, TCU_REG_OST_CNTL, &val);
+
+ return val;
+}
+
+static u64 notrace ingenic_ost_read_cnth(void)
+{
+ u32 val;
+
+ regmap_read(ingenic_ost->map, TCU_REG_OST_CNTH, &val);
+
+ return val;
+}
+
+static u64 notrace ingenic_ost_clocksource_read64(struct clocksource *cs)
+{
+ u32 val1, val2;
+ u64 count, recount;
+ s64 diff;
+
+ /*
+ * The buffering of the upper 32 bits of the timer prevents wrong
+ * results from the bottom 32 bits overflowing due to the timer ticking
+ * along. However, it does not prevent wrong results from simultaneous
+ * reads of the timer, which could reset the buffer mid-read.
+ * Since this kind of wrong read can happen only when the bottom bits
+ * overflow, there will be minutes between wrong reads, so if we read
+ * twice in succession, at least one of the reads will be correct.
+ */
+
+ /* Bypass the regmap here as we must return as soon as possible */
+ regmap_read(ingenic_ost->map, TCU_REG_OST_CNTL, &val1);
+ regmap_read(ingenic_ost->map, TCU_REG_OST_CNTHBUF, &val2);
+ count = (u64)val1 | (u64)val2 << 32;
+
+ regmap_read(ingenic_ost->map, TCU_REG_OST_CNTL, &val1);
+ regmap_read(ingenic_ost->map, TCU_REG_OST_CNTHBUF, &val2);
+ recount = (u64)val1 | (u64)val2 << 32;
+
+ /*
+ * A wrong read will produce a result that is 1<<32 too high: the bottom
+ * part from before overflow and the upper part from after overflow.
+ * Therefore, the lower value of the two reads is the correct value.
+ */
+
+ diff = (s64)(recount - count);
+ if (unlikely(diff < 0))
+ count = recount;
+
+ return count;
+}
+
+static u64 notrace ingenic_ost_clocksource_read32(struct clocksource *cs)
+{
+ return ingenic_ost_read_cnth();
+}
+
+static int __init ingenic_ost_probe(struct platform_device *pdev)
+{
+ const struct ingenic_ost_soc_info *soc_info;
+ struct device *dev = &pdev->dev;
+ struct ingenic_ost *ost;
+ struct clocksource *cs;
+ unsigned long rate;
+ int err;
+
+ soc_info = device_get_match_data(dev);
+ if (!soc_info)
+ return -EINVAL;
+
+ ost = devm_kzalloc(dev, sizeof(*ost), GFP_KERNEL);
+ if (!ost)
+ return -ENOMEM;
+
+ ingenic_ost = ost;
+
+ ost->map = device_node_to_regmap(dev->parent->of_node);
+ if (!ost->map) {
+ dev_err(dev, "regmap not found\n");
+ return -EINVAL;
+ }
+
+ ost->clk = devm_clk_get(dev, "ost");
+ if (IS_ERR(ost->clk))
+ return PTR_ERR(ost->clk);
+
+ err = clk_prepare_enable(ost->clk);
+ if (err)
+ return err;
+
+ /* Clear counter high/low registers */
+ if (soc_info->is64bit)
+ regmap_write(ost->map, TCU_REG_OST_CNTL, 0);
+ regmap_write(ost->map, TCU_REG_OST_CNTH, 0);
+
+ /* Don't reset counter at compare value. */
+ regmap_update_bits(ost->map, TCU_REG_OST_TCSR,
+ TCU_OST_TCSR_MASK, TCU_OST_TCSR_CNT_MD);
+
+ rate = clk_get_rate(ost->clk);
+
+ /* Enable OST TCU channel */
+ regmap_write(ost->map, TCU_REG_TESR, BIT(TCU_OST_CHANNEL));
+
+ cs = &ost->cs;
+ cs->name = "ingenic-ost";
+ cs->rating = 320;
+ cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;
+
+ if (soc_info->is64bit) {
+ cs->mask = CLOCKSOURCE_MASK(64);
+ cs->read = ingenic_ost_clocksource_read64;
+ } else {
+ cs->mask = CLOCKSOURCE_MASK(32);
+ cs->read = ingenic_ost_clocksource_read32;
+ }
+
+ err = clocksource_register_hz(cs, rate);
+ if (err) {
+ dev_err(dev, "clocksource registration failed: %d\n", err);
+ clk_disable_unprepare(ost->clk);
+ return err;
+ }
+
+ if (soc_info->is64bit)
+ sched_clock_register(ingenic_ost_read_cntl, 32, rate);
+ else
+ sched_clock_register(ingenic_ost_read_cnth, 32, rate);
+
+ return 0;
+}
+
+static int __maybe_unused ingenic_ost_suspend(struct device *dev)
+{
+ struct ingenic_ost *ost = dev_get_drvdata(dev);
+
+ clk_disable(ost->clk);
+
+ return 0;
+}
+
+static int __maybe_unused ingenic_ost_resume(struct device *dev)
+{
+ struct ingenic_ost *ost = dev_get_drvdata(dev);
+
+ return clk_enable(ost->clk);
+}
+
+static const struct dev_pm_ops __maybe_unused ingenic_ost_pm_ops = {
+ /* _noirq: We want the OST clock to be gated last / ungated first */
+ .suspend_noirq = ingenic_ost_suspend,
+ .resume_noirq = ingenic_ost_resume,
+};
+
+static const struct ingenic_ost_soc_info jz4725b_ost_soc_info = {
+ .is64bit = false,
+};
+
+static const struct ingenic_ost_soc_info jz4770_ost_soc_info = {
+ .is64bit = true,
+};
+
+static const struct of_device_id ingenic_ost_of_match[] = {
+ { .compatible = "ingenic,jz4725b-ost", .data = &jz4725b_ost_soc_info, },
+ { .compatible = "ingenic,jz4770-ost", .data = &jz4770_ost_soc_info, },
+ { }
+};
+
+static struct platform_driver ingenic_ost_driver = {
+ .driver = {
+ .name = "ingenic-ost",
+#ifdef CONFIG_PM_SUSPEND
+ .pm = &ingenic_ost_pm_ops,
+#endif
+ .of_match_table = ingenic_ost_of_match,
+ },
+};
+builtin_platform_driver_probe(ingenic_ost_driver, ingenic_ost_probe);
--
2.24.1
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