timer: add High Precision Event Timers (HPET) support

Adding HPET as an alternative timer for x86 (default is TSC). HPET counter has constant frequency and does not need calibration. This change also makes TSC timer driver optional on x86. If X86_TSC is disabled, early timer functions are provided by HPET.

Signed-off-by Ivan Gorinov <[email protected]>

---
 arch/Kconfig               |   2 +-
 arch/x86/dts/hpet.dtsi     |   7 ++
 drivers/timer/Kconfig      |   6 ++
 drivers/timer/Makefile     |   1 +
 drivers/timer/hpet_timer.c | 191 +++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 206 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/dts/hpet.dtsi
 create mode 100644 drivers/timer/hpet_timer.c

arch/Kconfig +1 -1

index e599e7a..37dabae 100644
@@ -104,7 +104,7 @@ config X86
        select DM_PCI
        select PCI
        select TIMER
-       select X86_TSC_TIMER
+       imply X86_TSC_TIMER
        imply BLK
        imply DM_ETH
        imply DM_GPIO

arch/x86/dts/hpet.dtsi new file +0 -0

new file mode 100644
index 0000000..037dc7e

arch/x86/dts/hpet.dtsi new file +5 -0

+               compatible = "hpet-x86";
+               u-boot,dm-pre-reloc;
+               reg = <0xfed00000 0x1000>;
+       };
+};

drivers/timer/Kconfig +6 -0

index 2c96896..72ae6c5 100644
@@ -65,6 +65,12 @@ config X86_TSC_TIMER
        help
          Select this to enable Time-Stamp Counter (TSC) timer for x86.
 
+config HPET_TIMER
+       bool "High Precision Event Timers (HPET) support"
+       depends on TIMER && X86
+       help
+         Select this to enable High Precision Event Timers (HPET) for x86.
+
 config OMAP_TIMER
        bool "Omap timer support"
        depends on TIMER

drivers/timer/Makefile +1 -0

index a6e7832..557fecc 100644
@@ -8,6 +8,7 @@ obj-y += timer-uclass.o
 obj-$(CONFIG_ALTERA_TIMER)     += altera_timer.o
 obj-$(CONFIG_SANDBOX_TIMER)    += sandbox_timer.o
 obj-$(CONFIG_X86_TSC_TIMER)    += tsc_timer.o
+obj-$(CONFIG_HPET_TIMER)       += hpet_timer.o
 obj-$(CONFIG_OMAP_TIMER)       += omap-timer.o
 obj-$(CONFIG_AST_TIMER)        += ast_timer.o
 obj-$(CONFIG_STI_TIMER)                += sti-timer.o

drivers/timer/hpet_timer.c new file +12 -0

new file mode 100644
index 0000000..0bef859
@@ -0,0 +1,191 @@
+/*
+ * Copyright (c) 2017 Intel Corporation
+ *
+ * SPDX-License-Identifier:    GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <malloc.h>
+#include <timer.h>
+#include <asm/cpu.h>
+#include <asm/io.h>

drivers/timer/hpet_timer.c new file +19 -0

+
+struct hpet_timer_priv {
+       void *regs;
+};
+
+/*
+ * Returns HPET clock frequency in HZ
+ * (rounding to the nearest integer),
+ * or 0 if HPET is not available.
+ */
+static inline u32 get_clock_frequency(void *regs)
+{
+       u64 d = 1000000000000000ull;
+       u32 period;
+
+       period = readl(regs + HPET_PERIOD_REG);
+       if (period == 0)
+               return 0;
+       if (period > HPET_MAX_PERIOD)

drivers/timer/hpet_timer.c new file +53 -0

+static void start_main_counter(void *regs)
+{
+       u32 config;
+
+       config = readl(regs + HPET_CONFIG_REG);
+       config &= ~1;
+       writel(config, regs + HPET_CONFIG_REG);
+       writel(0, regs + HPET_MAIN_COUNT_L);
+       writel(0, regs + HPET_MAIN_COUNT_H);
+       config |= 1;
+       writel(config, regs + HPET_CONFIG_REG);
+}
+
+/*
+ * Read the main counter as two 32-bit registers,
+ * repeat if rollover happens.
+ */
+static u64 read_main_counter(void *regs)
+{
+       u64 now_tick;
+       u32 tl, th, th0;
+
+       th = readl(regs + HPET_MAIN_COUNT_H);
+       do {
+               th0 = th;
+               tl = readl(regs + HPET_MAIN_COUNT_L);
+               th = readl(regs + HPET_MAIN_COUNT_H);
+       } while (th != th0);
+
+       now_tick = th;
+       now_tick <<= 32;
+       now_tick |= tl;
+
+       return now_tick;
+}
+
+static int hpet_timer_get_count(struct udevice *dev, u64 *count)
+{
+       struct hpet_timer_priv *priv = dev_get_priv(dev);
+
+       *count = read_main_counter(priv->regs);
+
+       return 0;
+}
+
+static int hpet_timer_probe(struct udevice *dev)
+{
+       struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+       struct hpet_timer_priv *priv = dev_get_priv(dev);
+       u32 rate;
+
+       rate = get_clock_frequency(priv->regs);
+       if (rate == 0)

drivers/timer/hpet_timer.c new file +68 -0

+
+static void *early_regs = (void *) CONFIG_HPET_ADDRESS;
+
+unsigned long notrace timer_early_get_rate(void)
+{
+       return get_clock_frequency(early_regs);
+}
+
+u64 notrace timer_early_get_count(void)
+{
+       return read_main_counter(early_regs);
+}
+
+int timer_init(void)
+{
+       if (get_clock_frequency(early_regs) == 0)
+               return -ENODEV;
+
+       start_main_counter(early_regs);
+
+       return 0;
+}
+
+ulong timer_get_boot_us(void)
+{
+       u32 period;
+       u64 d;
+
+       period = readl(early_regs + HPET_PERIOD_REG);
+       if (period == 0)
+               return 0;
+       if (period > HPET_MAX_PERIOD)
+               return 0;
+
+       d = read_main_counter(early_regs);
+
+       /*
+        * Multiplication overflow
+        * at 2^64 femtoseconds
+        * (more than 5 hours)
+        */
+
+       d *= period;
+
+       return d / 1000000000;
+}
+
+#endif /* CONFIG_X86_TSC_TIMER */
+
+static int hpet_timer_ofdata_to_platdata(struct udevice *dev)
+{
+       struct hpet_timer_priv *priv = dev_get_priv(dev);
+       priv->regs = map_physmem(devfdt_get_addr(dev), 0x1000, MAP_NOCACHE);
+
+       return 0;
+}
+
+static const struct timer_ops hpet_timer_ops = {
+       .get_count = hpet_timer_get_count,
+};
+
+static const struct udevice_id hpet_timer_ids[] = {
+       { .compatible = "hpet-x86", },
+       { .compatible = "intel,ce4100-hpet", },
+       { }
+};
+
+U_BOOT_DRIVER(hpet_timer) = {

Adding HPET as an alternative timer for x86 (default is TSC). HPET counter has constant frequency and does not need calibration. This change also makes TSC timer driver optional on x86. If X86_TSC is disabled, early timer functions are provided by HPET.

Signed-off-by Ivan Gorinov <[email protected]>

---

drivers/timer/hpet_timer.c line 60

Quoted 2 lines

drivers/timer/hpet_timer.c new file +2 -0

+       writel(0, regs + HPET_MAIN_COUNT_L);
+       writel(0, regs + HPET_MAIN_COUNT_H);

Can we use writeq() here?

drivers/timer/hpet_timer.c line 78

Quoted 2 lines

drivers/timer/hpet_timer.c new file +2 -0

+               tl = readl(regs + HPET_MAIN_COUNT_L);
+               th = readl(regs + HPET_MAIN_COUNT_H);

Ditto.

Quoted 4 lines · Andy Shevchenko

drivers/timer/hpet_timer.c line 60

Quoted 2 lines

drivers/timer/hpet_timer.c new file +2 -0

+       writel(0, regs + HPET_MAIN_COUNT_L);
+       writel(0, regs + HPET_MAIN_COUNT_H);

Can we use writeq() here?

I don't see readq/writeq defined for x86, even x86_64.

Quoted 4 lines

drivers/timer/hpet_timer.c line 78

Quoted 2 lines

drivers/timer/hpet_timer.c new file +2 -0

+               tl = readl(regs + HPET_MAIN_COUNT_L);
+               th = readl(regs + HPET_MAIN_COUNT_H);

Ditto.

If readq() is defined as two read operations in 32-bit code, main counter rollover (low part overflow, high part increment) can happen between them.

Quoted 7 lines

Quoted 4 lines

drivers/timer/hpet_timer.c line 78

Quoted 2 lines

drivers/timer/hpet_timer.c new file +2 -0

+               tl = readl(regs + HPET_MAIN_COUNT_L);
+               th = readl(regs + HPET_MAIN_COUNT_H);

Ditto.

If readq() is defined as two read operations in 32-bit code, main counter rollover (low part overflow, high part increment) can happen between them.

And how this contradicts ther current code?

Quoted 3 lines · Andy Shevchenko

Quoted 3 lines

Quoted 3 lines

Quoted 2 lines

drivers/timer/hpet_timer.c new file +2 -0

+               tl = readl(regs + HPET_MAIN_COUNT_L);
+               th = readl(regs + HPET_MAIN_COUNT_H);

Quoted 6 lines

Quoted 4 lines

Quoted 1 line

Ditto.

If readq() is defined as two read operations in 32-bit code, main counter rollover (low part overflow, high part increment) can happen between them.

And how this contradicts ther current code?

It just does not make the code simpler,

rollover check is
still required if U-Boot is compiled as 32-bit code.

Can we do something like the following?

#ifdef CONFIG_X86_64

static u64 read_main_counter(void *regs)

{
        return readq(regs + HPET_MAIN_COUNT);
}

#else

/*
* Read the main counter as two 32-bit registers,
* repeat if rollover happens.
*/
static u64 read_main_counter(void *regs)

{
        u64 now_tick;
        u32 tl, th, th0;

        th = readl(regs + HPET_MAIN_COUNT_H);
        do {

                th0 = th;
                tl = readl(regs + HPET_MAIN_COUNT_L);
                th = readl(regs + HPET_MAIN_COUNT_H);
                now_tick = th;
                now_tick <<= 32;
                now_tick |= tl;

        } while (th != th0);

        return now_tick;
}

#endif

Quoted 4 lines

Quoted 3 lines

Quoted 2 lines

If readq() is defined as two read operations in 32-bit code, main counter rollover (low part overflow, high part increment) can happen between them.

And how this contradicts ther current code?

It just does not make the code simpler,

...b/c you misread what I suggested.

Quoted 3 lines

rollover check is
still required if U-Boot is compiled as 32-bit code. Can we do something like the following?

Yes, but... why?
What's wrong with replacing two sequential 32-bit reads with one 64-bit?

Quoted 8 lines · Andy Shevchenko

Quoted 4 lines

Quoted 3 lines

Quoted 2 lines

If readq() is defined as two read operations in 32-bit code, main counter rollover (low part overflow, high part increment) can happen between them.

And how this contradicts ther current code?

It just does not make the code simpler,

...b/c you misread what I suggested.

Quoted 3 lines

rollover check is
still required if U-Boot is compiled as 32-bit code. Can we do something like the following?

Quoted 2 lines

Yes, but... why?
What's wrong with replacing two sequential 32-bit reads with one 64-bit?

Doesn't readX/writeX imply a single I/O operation? It may be misleading to define it as two.

Assuming MMX or SSE2 to be supported by all x86 processors, 64-bit I/O registers can be accessed as a single operation even in 32-bit code:

static inline u64 readq(void *addr)

{
        u64 value;

        asm volatile ("movq (%0), %%xmm0" : : "r" (addr));
        asm volatile ("movq %%xmm0, %0" : "=m" (value));

        return value;
}

I can add these definitions to "asm/io.h".

Quoted 6 lines

Doesn't readX/writeX imply a single I/O operation? It may be misleading to define it as two.

Assuming MMX or SSE2 to be supported by all x86 processors, 64-bit I/O registers can be accessed as a single operation even in 32-bit code:

Adding such requirement (MMX or SSE2) to U-Boot is not good. Why do we require MMX or SSE2 for readq? Can we use general purpose registers?

Quoted 12 lines

static inline u64 readq(void *addr)

{
        u64 value;

        asm volatile ("movq (%0), %%xmm0" : : "r" (addr));
        asm volatile ("movq %%xmm0, %0" : "=m" (value));

        return value;
}

I can add these definitions to "asm/io.h".

Quoted 4 lines · Andy Shevchenko

Quoted 4 lines

Quoted 3 lines

Quoted 2 lines

If readq() is defined as two read operations in 32-bit code, main counter rollover (low part overflow, high part increment) can happen between them.

And how this contradicts ther current code?

It just does not make the code simpler,

Quoted 6 lines

...b/c you misread what I suggested.

Quoted 3 lines

rollover check is
still required if U-Boot is compiled as 32-bit code. Can we do something like the following?

Yes, but... why?
What's wrong with replacing two sequential 32-bit reads with one 64-bit?

Doesn't readX/writeX imply a single I/O operation?

It may be misleading to define it as two.

Assuming MMX or SSE2 to be supported by all x86 processors, 64-bit I/O registers can be accessed as a single operation even in 32-bit code:

static inline u64 readq(void *addr)

{
        u64 value;

        asm volatile ("movq (%0), %%xmm0" : : "r" (addr));
        asm volatile ("movq %%xmm0, %0" : "=m" (value));

        return value;
}

I can add these definitions to "asm/io.h".

Quoted 7 lines · Bin Meng

Quoted 6 lines

Doesn't readX/writeX imply a single I/O operation? It may be misleading to define it as two.

Assuming MMX or SSE2 to be supported by all x86 processors, 64-bit I/O registers can be accessed as a single operation even in 32-bit code:

Quoted 2 lines

Adding such requirement (MMX or SSE2) to U-Boot is not good. Why do we require MMX or SSE2 for readq? Can we use general purpose registers?

In 32-bit code, we can't make a 64-bit memory read operation using only general purpose registers.