Re: [Qemu-devel] [PATCH v5 1/7] stm32f205_timer: Add the stm32f205 Timer

[Peter Crosthwaite]

Sorry about the review delay...

On Thu, Oct 16, 2014 at 10:53 PM, Alistair Francis <address@hidden> wrote:
> This patch adds the stm32f205 timers: TIM2, TIM3, TIM4 and TIM5
> to QEMU.
>
> Signed-off-by: Alistair Francis <address@hidden>
> ---
> V4:
>  - Update timer units again
>     - Thanks to Peter C
> V3:
>  - Update debug statements
>  - Correct the units for timer_mod
>  - Correctly set timer_offset from resets
> V2:
>  - Reorder the Makefile config
>  - Fix up the debug printing
>  - Correct the timer event trigger
> Changes from RFC:
>  - Small changes to functionality and style. Thanks to Peter C
>  - Rename to make the timer more generic
>  - Split the config settings to device level
>
>  default-configs/arm-softmmu.mak    |   1 +
>  hw/timer/Makefile.objs             |   2 +
>  hw/timer/stm32f205_timer.c         | 318 
> +++++++++++++++++++++++++++++++++++++
>  include/hw/timer/stm32f205_timer.h | 101 ++++++++++++
>  4 files changed, 422 insertions(+)
>  create mode 100644 hw/timer/stm32f205_timer.c
>  create mode 100644 include/hw/timer/stm32f205_timer.h
>
> diff --git a/default-configs/arm-softmmu.mak b/default-configs/arm-softmmu.mak
> index f3513fa..cf23b24 100644
> --- a/default-configs/arm-softmmu.mak
> +++ b/default-configs/arm-softmmu.mak
> @@ -78,6 +78,7 @@ CONFIG_NSERIES=y
>  CONFIG_REALVIEW=y
>  CONFIG_ZAURUS=y
>  CONFIG_ZYNQ=y
> +CONFIG_STM32F205_TIMER=y
>
>  CONFIG_VERSATILE_PCI=y
>  CONFIG_VERSATILE_I2C=y
> diff --git a/hw/timer/Makefile.objs b/hw/timer/Makefile.objs
> index 2c86c3d..4bd9617 100644
> --- a/hw/timer/Makefile.objs
> +++ b/hw/timer/Makefile.objs
> @@ -31,3 +31,5 @@ obj-$(CONFIG_DIGIC) += digic-timer.o
>  obj-$(CONFIG_MC146818RTC) += mc146818rtc.o
>
>  obj-$(CONFIG_ALLWINNER_A10_PIT) += allwinner-a10-pit.o
> +
> +common-obj-$(CONFIG_STM32F205_TIMER) += stm32f205_timer.o
> diff --git a/hw/timer/stm32f205_timer.c b/hw/timer/stm32f205_timer.c
> new file mode 100644
> index 0000000..aace8df
> --- /dev/null
> +++ b/hw/timer/stm32f205_timer.c
> @@ -0,0 +1,318 @@
> +/*
> + * STM32F205 Timer

ST doc RM0033 which docs this timer refers to a larger family of SOCs.
I think you can change this from 205 to 2XX probably globally for the
series.

> + *
> + * Copyright (c) 2014 Alistair Francis <address@hidden>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a 
> copy
> + * of this software and associated documentation files (the "Software"), to 
> deal
> + * in the Software without restriction, including without limitation the 
> rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
> FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#include "hw/timer/stm32f205_timer.h"
> +
> +#ifndef STM_TIMER_ERR_DEBUG
> +#define STM_TIMER_ERR_DEBUG 0
> +#endif
> +
> +#define DB_PRINT_L(lvl, fmt, args...) do { \
> +    if (STM_TIMER_ERR_DEBUG >= lvl) { \
> +        qemu_log("%s: " fmt, __func__, ## args); \
> +    } \
> +} while (0);
> +
> +#define DB_PRINT(fmt, args...) DB_PRINT_L(1, fmt, ## args)
> +
> +static void stm32f205_timer_set_alarm(STM32f205TimerState *s);
> +
> +static void stm32f205_timer_interrupt(void *opaque)
> +{
> +    STM32f205TimerState *s = opaque;
> +
> +    DB_PRINT("Interrupt\n");
> +
> +    if (s->tim_dier & TIM_DIER_UIE && s->tim_cr1 & TIM_CR1_CEN) {
> +        s->tim_sr |= 1;
> +        qemu_irq_pulse(s->irq);
> +        stm32f205_timer_set_alarm(s);
> +    }
> +}
> +
> +static void stm32f205_timer_set_alarm(STM32f205TimerState *s)
> +{
> +    uint32_t ticks;
> +    int64_t now;
> +
> +    DB_PRINT("Alarm set at: 0x%x\n", s->tim_cr1);
> +
> +    now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);

So now is in terms of ms.

> +    ticks = s->tim_arr - ((s->tick_offset + (now * (s->freq_hz / 1000))) /

tick_offset is terms of clock-cycles-before-prescalar. ticks and
tim_arr must be in terms of clock-cycles-post-pre-scalar.

I'm slightly hazy on definition of tick_offset but i'm guessing its
the time offset of when the timer started expressed in
before-prescalar cycles? I would then expect this to be:

ticks = tim_arr - (now * (scale) - tick_offset).

with (now * scale - tick_offset) / tim_psc corresponding to the
current value of the running timer (tim_cnt?).

> +            (s->tim_psc + 1));

So in total this expression is calculating a number of clock cycles
until a hit as "ticks".

> +
> +    DB_PRINT("Alarm set in %d ticks\n", ticks);
> +
> +    if (ticks == 0) {

What if ticks is -ve due to a late callback of set_alarm? It will
probably work, but it seems inconsistent that you rely on the callback
path for -ve and +ve tick balances but have a fast path for when ticks
happens to balance to exactly 0. This fast path should probably handle
-ve's or you could just ditch it entirely.

> +        timer_del(s->timer);
> +        stm32f205_timer_interrupt(s);
> +    } else {
> +        timer_mod(s->timer, ((now * (s->freq_hz / 1000)) / (s->tim_psc + 1)) 
> +

Common sub-expression  (now * (s->freq_hz / 1000)) / (s->tim_psc + 1)
with calculation of "ticks" above can be cached in a variable. but ...

> +                             (int64_t) ticks);

this calculation has me confused. My understanding is timer_mode
should be given an absolute value as time. s->timer is defined as a ns
timer whereas this calculation is a clock cycles value.

> +        DB_PRINT("Wait Time: %" PRId64 " ticks\n",
> +                 ((now * (s->freq_hz / 1000)) / (s->tim_psc + 1)) +
> +                 (int64_t) ticks);
> +    }
> +}
> +
> +static void stm32f205_timer_reset(DeviceState *dev)
> +{
> +    STM32f205TimerState *s = STM32F205TIMER(dev);
> +
> +    s->tim_cr1 = 0;
> +    s->tim_cr2 = 0;
> +    s->tim_smcr = 0;
> +    s->tim_dier = 0;
> +    s->tim_sr = 0;
> +    s->tim_egr = 0;
> +    s->tim_ccmr1 = 0;
> +    s->tim_ccmr2 = 0;
> +    s->tim_ccer = 0;
> +    s->tim_cnt = 0;
> +    s->tim_psc = 0;
> +    s->tim_arr = 0;
> +    s->tim_ccr1 = 0;
> +    s->tim_ccr2 = 0;
> +    s->tim_ccr3 = 0;
> +    s->tim_ccr4 = 0;
> +    s->tim_dcr = 0;
> +    s->tim_dmar = 0;
> +    s->tim_or = 0;
> +
> +    s->tick_offset = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) *
> +                     (s->freq_hz / 1000);
> +}
> +
> +static uint64_t stm32f205_timer_read(void *opaque, hwaddr offset,
> +                           unsigned size)
> +{
> +    STM32f205TimerState *s = opaque;
> +
> +    DB_PRINT("Read 0x%"HWADDR_PRIx"\n", offset);
> +
> +    switch (offset) {
> +    case TIM_CR1:
> +        return s->tim_cr1;
> +    case TIM_CR2:
> +        return s->tim_cr2;
> +    case TIM_SMCR:
> +        return s->tim_smcr;
> +    case TIM_DIER:
> +        return s->tim_dier;
> +    case TIM_SR:
> +        return s->tim_sr;
> +    case TIM_EGR:
> +        return s->tim_egr;
> +    case TIM_CCMR1:
> +        return s->tim_ccmr1;
> +    case TIM_CCMR2:
> +        return s->tim_ccmr2;
> +    case TIM_CCER:
> +        return s->tim_ccer;
> +    case TIM_CNT:
> +        s->tim_cnt = s->tick_offset + (qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) 
> *
> +                                       (s->freq_hz / 1000));

Same comment above about subbing tick_offset rather than adding.

> +        return s->tim_cnt;
> +    case TIM_PSC:
> +        return s->tim_psc;
> +    case TIM_ARR:
> +        return s->tim_arr;
> +    case TIM_CCR1:
> +        return s->tim_ccr1;
> +    case TIM_CCR2:
> +        return s->tim_ccr2;
> +    case TIM_CCR3:
> +        return s->tim_ccr3;
> +    case TIM_CCR4:
> +        return s->tim_ccr4;
> +    case TIM_DCR:
> +        return s->tim_dcr;
> +    case TIM_DMAR:
> +        return s->tim_dmar;
> +    case TIM_OR:
> +        return s->tim_or;
> +    default:
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, offset);
> +    }
> +
> +    return 0;
> +}
> +
> +static void stm32f205_timer_write(void *opaque, hwaddr offset,
> +                        uint64_t val64, unsigned size)
> +{
> +    STM32f205TimerState *s = opaque;
> +    uint32_t value = val64;
> +
> +    DB_PRINT("Write 0x%x, 0x%"HWADDR_PRIx"\n", value, offset);
> +
> +    switch (offset) {
> +    case TIM_CR1:
> +        s->tim_cr1 = value;
> +        return;
> +    case TIM_CR2:
> +        s->tim_cr2 = value;
> +        return;
> +    case TIM_SMCR:
> +        s->tim_smcr = value;
> +        return;
> +    case TIM_DIER:
> +        s->tim_dier = value;
> +        return;
> +    case TIM_SR:
> +        /* This is set by hardware and cleared by software */
> +        s->tim_sr &= value;
> +        return;
> +    case TIM_EGR:
> +        s->tim_egr = value;
> +        if (s->tim_egr & TIM_EGR_UG) {
> +            /* Re-init the counter */
> +            stm32f205_timer_reset(DEVICE(s));
> +        }
> +        return;
> +    case TIM_CCMR1:
> +        s->tim_ccmr1 = value;
> +        return;
> +    case TIM_CCMR2:
> +        s->tim_ccmr2 = value;
> +        return;
> +    case TIM_CCER:
> +        s->tim_ccer = value;
> +        return;
> +    case TIM_CNT:
> +        s->tim_cnt = value;

You set tim_cnt here, presumably setting the value of the timer. But
set_alarm doesn't do anything with it. You need to warp tick_offset
here to account for the new 0-base of the timer. When I run into this
situation though, i generally use a two-variable approach where I have
both the value of the timer and the VM timer corresponding to it e.g.

uint32_t timer_val; /* value of timer in clock cycles */
uint64_t sync_time; /* VM time for when timer_val last updated */

And not bother trying to maintain an absolute (0-based) tick offset.
Then every time someone touches a prescalar, timer-value,
enable-switch, etc etc you just sync these two numbers first:

now = qemu_get_clock
timer_val += (now - sync_time) * scale(); /* scale is 0 for a disabled timer */
sync_time = now;

Then do your thing. Then delete or re-arm the callback if needed.

Otherwise you need a sync() pair much like the ones we used for the
ARM PMCCNTR around some of these ops.

> +        stm32f205_timer_set_alarm(s);
> +        return;
> +    case TIM_PSC:
> +        s->tim_psc = value;

Change the prescaler requires a rearming of the callback as it can
have an affect on the calculation of "ticks".

> +        return;
> +    case TIM_ARR:
> +        s->tim_arr = value;
> +        stm32f205_timer_set_alarm(s);
> +        return;
> +    case TIM_CCR1:
> +        s->tim_ccr1 = value;
> +        return;
> +    case TIM_CCR2:
> +        s->tim_ccr2 = value;
> +        return;
> +    case TIM_CCR3:
> +        s->tim_ccr3 = value;
> +        return;
> +    case TIM_CCR4:
> +        s->tim_ccr4 = value;
> +        return;
> +    case TIM_DCR:
> +        s->tim_dcr = value;
> +        return;
> +    case TIM_DMAR:
> +        s->tim_dmar = value;
> +        return;
> +    case TIM_OR:
> +        s->tim_or = value;
> +        return;
> +    default:
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, offset);
> +    }
> +}
> +
> +static const MemoryRegionOps stm32f205_timer_ops = {
> +    .read = stm32f205_timer_read,
> +    .write = stm32f205_timer_write,
> +    .endianness = DEVICE_NATIVE_ENDIAN,
> +};
> +
> +static const VMStateDescription vmstate_stm32f205_timer = {
> +    .name = TYPE_STM32F205_TIMER,
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT32(tick_offset, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_cr1, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_cr2, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_smcr, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_dier, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_sr, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_egr, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_ccmr1, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_ccmr2, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_ccer, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_cnt, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_psc, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_arr, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_ccr1, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_ccr2, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_ccr3, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_ccr4, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_dcr, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_dmar, STM32f205TimerState),
> +        VMSTATE_UINT32(tim_or, STM32f205TimerState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static Property stm32f205_timer_properties[] = {
> +    DEFINE_PROP_UINT64("clock-frequency", struct STM32f205TimerState,
> +                       freq_hz, 1000000000),

With 1GHz precision should you be using ns timing throughout instead
of ms? You may need to add some muldivs to account for the bigger
numbers.

Regards,
Peter

> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void stm32f205_timer_init(Object *obj)
> +{
> +    STM32f205TimerState *s = STM32F205TIMER(obj);
> +
> +    sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->irq);
> +
> +    memory_region_init_io(&s->iomem, obj, &stm32f205_timer_ops, s,
> +                          "stm32f205_timer", 0x2000);
> +    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->iomem);
> +
> +    s->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, stm32f205_timer_interrupt, 
> s);
> +}
> +
> +static void stm32f205_timer_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +
> +    dc->reset = stm32f205_timer_reset;
> +    dc->props = stm32f205_timer_properties;
> +    dc->vmsd = &vmstate_stm32f205_timer;
> +}
> +
> +static const TypeInfo stm32f205_timer_info = {
> +    .name          = TYPE_STM32F205_TIMER,
> +    .parent        = TYPE_SYS_BUS_DEVICE,
> +    .instance_size = sizeof(STM32f205TimerState),
> +    .instance_init = stm32f205_timer_init,
> +    .class_init    = stm32f205_timer_class_init,
> +};
> +
> +static void stm32f205_timer_register_types(void)
> +{
> +    type_register_static(&stm32f205_timer_info);
> +}
> +
> +type_init(stm32f205_timer_register_types)
> diff --git a/include/hw/timer/stm32f205_timer.h 
> b/include/hw/timer/stm32f205_timer.h
> new file mode 100644
> index 0000000..9425cb1
> --- /dev/null
> +++ b/include/hw/timer/stm32f205_timer.h
> @@ -0,0 +1,101 @@
> +/*
> + * STM32F205 Timer
> + *
> + * Copyright (c) 2014 Alistair Francis <address@hidden>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a 
> copy
> + * of this software and associated documentation files (the "Software"), to 
> deal
> + * in the Software without restriction, including without limitation the 
> rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
> FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#ifndef HW_STM_TIMER_H
> +#define HW_STM_TIMER_H
> +
> +#include "hw/sysbus.h"
> +#include "qemu/timer.h"
> +#include "sysemu/sysemu.h"
> +
> +#define TIM_CR1      0x00
> +#define TIM_CR2      0x04
> +#define TIM_SMCR     0x08
> +#define TIM_DIER     0x0C
> +#define TIM_SR       0x10
> +#define TIM_EGR      0x14
> +#define TIM_CCMR1    0x18
> +#define TIM_CCMR2    0x1C
> +#define TIM_CCER     0x20
> +#define TIM_CNT      0x24
> +#define TIM_PSC      0x28
> +#define TIM_ARR      0x2C
> +#define TIM_CCR1     0x34
> +#define TIM_CCR2     0x38
> +#define TIM_CCR3     0x3C
> +#define TIM_CCR4     0x40
> +#define TIM_DCR      0x48
> +#define TIM_DMAR     0x4C
> +#define TIM_OR       0x50
> +
> +#define TIM_CR1_CEN   1
> +
> +#define TIM_EGR_UG 1
> +
> +#define TIM_CCER_CC2E   (1 << 4)
> +#define TIM_CCMR1_OC2M2 (1 << 14)
> +#define TIM_CCMR1_OC2M1 (1 << 13)
> +#define TIM_CCMR1_OC2M0 (1 << 12)
> +#define TIM_CCMR1_OC2PE (1 << 11)
> +
> +#define TIM_DIER_UIE  1
> +
> +#define TYPE_STM32F205_TIMER "stm32f205-timer"
> +#define STM32F205TIMER(obj) OBJECT_CHECK(STM32f205TimerState, \
> +                            (obj), TYPE_STM32F205_TIMER)
> +
> +typedef struct STM32f205TimerState {
> +    /* <private> */
> +    SysBusDevice parent_obj;
> +
> +    /* <public> */
> +    MemoryRegion iomem;
> +    QEMUTimer *timer;
> +    qemu_irq irq;
> +
> +    uint32_t tick_offset;
> +    uint64_t freq_hz;
> +
> +    uint32_t tim_cr1;
> +    uint32_t tim_cr2;
> +    uint32_t tim_smcr;
> +    uint32_t tim_dier;
> +    uint32_t tim_sr;
> +    uint32_t tim_egr;
> +    uint32_t tim_ccmr1;
> +    uint32_t tim_ccmr2;
> +    uint32_t tim_ccer;
> +    uint32_t tim_cnt;
> +    uint32_t tim_psc;
> +    uint32_t tim_arr;
> +    uint32_t tim_ccr1;
> +    uint32_t tim_ccr2;
> +    uint32_t tim_ccr3;
> +    uint32_t tim_ccr4;
> +    uint32_t tim_dcr;
> +    uint32_t tim_dmar;
> +    uint32_t tim_or;
> +} STM32f205TimerState;
> +
> +#endif
> --
> 1.9.1
>
>