Re: [PATCH V2 2/6] clocksource: tegra: add Tegra210 timer driver
From: Joseph Lo
Date: Mon Jan 28 2019 - 22:35:28 EST
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@xxxxxxxxxx>
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Joseph Lo <josephl@xxxxxxxxxx>
---
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