Re: [PATCH qemu] Add basic power management to raspi.

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Hi Nolan,

Thanks for your patch!

There is something odd with your email address, which apparently
became sourcehut@sigbus.net instead of nolan@sigbus.net.

On 5/18/21 10:24 PM, ~nolanl wrote:
> From: Nolan Leake <nolan@sigbus.net>
> 
> This is just enough to make reboot and poweroff work.

Please precise "for Linux kernels", since this doesn't work
with firmwares (ideally we should implement the FIRMWARE_NOTIFY_REBOOT
property - which Linux sends - to handle the machine reboot/halt
via the videocore firmware model).

> Notably, the
> watchdog timer functionality is not yet implemented.
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/64
> Signed-off-by: Nolan Leake <nolan@sigbus.net>
> ---
>  hw/arm/bcm2835_peripherals.c         |  13 ++-
>  hw/misc/bcm2835_powermgt.c           | 157 +++++++++++++++++++++++++++
>  hw/misc/meson.build                  |   1 +
>  include/hw/arm/bcm2835_peripherals.h |   3 +-
>  include/hw/misc/bcm2835_powermgt.h   |  29 +++++
>  5 files changed, 201 insertions(+), 2 deletions(-)
>  create mode 100644 hw/misc/bcm2835_powermgt.c
>  create mode 100644 include/hw/misc/bcm2835_powermgt.h
> 
> diff --git a/hw/arm/bcm2835_peripherals.c b/hw/arm/bcm2835_peripherals.c
> index dcff13433e..48538c9360 100644
> --- a/hw/arm/bcm2835_peripherals.c
> +++ b/hw/arm/bcm2835_peripherals.c
> @@ -126,6 +126,10 @@ static void bcm2835_peripherals_init(Object *obj)
>  
>      object_property_add_const_link(OBJECT(&s->dwc2), "dma-mr",
>                                     OBJECT(&s->gpu_bus_mr));
> +
> +    /* Power Management */
> +    object_initialize_child(obj, "powermgt", &s->powermgt,
> +                            TYPE_BCM2835_POWERMGT);
>  }
>  
>  static void bcm2835_peripherals_realize(DeviceState *dev, Error **errp)
> @@ -364,9 +368,16 @@ static void bcm2835_peripherals_realize(DeviceState *dev, Error **errp)
>          qdev_get_gpio_in_named(DEVICE(&s->ic), BCM2835_IC_GPU_IRQ,
>                                 INTERRUPT_USB));
>  
> +    /* Power Management */
> +    if (!sysbus_realize(SYS_BUS_DEVICE(&s->powermgt), errp)) {
> +        return;
> +    }
> +
> +    memory_region_add_subregion(&s->peri_mr, PM_OFFSET,
> +                sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->powermgt), 0));
> +
>      create_unimp(s, &s->txp, "bcm2835-txp", TXP_OFFSET, 0x1000);
>      create_unimp(s, &s->armtmr, "bcm2835-sp804", ARMCTRL_TIMER0_1_OFFSET, 0x40);
> -    create_unimp(s, &s->powermgt, "bcm2835-powermgt", PM_OFFSET, 0x114);
>      create_unimp(s, &s->i2s, "bcm2835-i2s", I2S_OFFSET, 0x100);
>      create_unimp(s, &s->smi, "bcm2835-smi", SMI_OFFSET, 0x100);
>      create_unimp(s, &s->spi[0], "bcm2835-spi0", SPI0_OFFSET, 0x20);
> diff --git a/hw/misc/bcm2835_powermgt.c b/hw/misc/bcm2835_powermgt.c
> new file mode 100644
> index 0000000000..81107ecc8f
> --- /dev/null
> +++ b/hw/misc/bcm2835_powermgt.c
> @@ -0,0 +1,157 @@
> +/*
> + * BCM2835 Power Management emulation
> + *
> + * Copyright (C) 2017 Marcin Chojnacki <marcinch7@gmail.com>
> + * Copyright (C) 2021 Nolan Leake <nolan@sigbus.net>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/log.h"
> +#include "qemu/module.h"
> +#include "hw/misc/bcm2835_powermgt.h"
> +#include "migration/vmstate.h"
> +#include "sysemu/runstate.h"
> +
> +#define PASSWORD 0x5a000000
> +#define PASSWORD_MASK 0xff000000
> +
> +#define R_RSTC 0x1c
> +#define V_RSTC_RESET 0x20
> +#define R_RSTS 0x20
> +#define V_RSTS_POWEROFF 0x555
> +#define R_WDOG 0x24
> +
> +static uint64_t bcm2835_powermgt_read(void *opaque, hwaddr offset,
> +                                      unsigned size)
> +{
> +    BCM2835PowerMgtState *s = (BCM2835PowerMgtState *)opaque;
> +    uint32_t res = 0;
> +
> +    assert(size == 4);

Instead of this assert, add in bcm2835_powermgt_ops:

  .impl.min_access_size = 4,
  .impl.max_access_size = 4,

> +
> +    switch (offset) {
> +    case R_RSTC:
> +        res = s->rstc;
> +        break;
> +    case R_RSTS:
> +        res = s->rsts;
> +        break;
> +    case R_WDOG:
> +        res = s->wdog;
> +        break;
> +
> +    default:
> +        qemu_log_mask(LOG_UNIMP,
> +                      "bcm2835_powermgt_read: Unknown offset %x\n",
> +                      (int)offset);
> +        res = 0;
> +        break;
> +    }
> +
> +    return res;
> +}
> +
> +static void bcm2835_powermgt_write(void *opaque, hwaddr offset,
> +                                   uint64_t value, unsigned size)
> +{
> +    BCM2835PowerMgtState *s = (BCM2835PowerMgtState *)opaque;
> +
> +    assert(size == 4);

(remove this assert too).

> +    if ((value & PASSWORD_MASK) != PASSWORD) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "bcm2835_powermgt_write: Bad password %x at offset %x\n",

Please prefix hexadecimal formats with 0x,

> +                      (uint32_t)value, (int)offset);

and do not cast.

> +        return;
> +    }
> +
> +    value = value & ~PASSWORD_MASK;
> +
> +    switch (offset) {
> +    case R_RSTC:
> +        s->rstc = value;
> +        if (value & V_RSTC_RESET) {
> +            if ((s->rsts & 0xfff) == V_RSTS_POWEROFF) {
> +                /* Linux uses partition 63 to indicate halt. */

I'd move this comment with the V_RSTS_POWEROFF definition.

> +                qemu_system_shutdown_request(SHUTDOWN_CAUSE_GUEST_SHUTDOWN);
> +            } else {
> +                qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
> +            }
> +        }

Shouldn't we log the unsupported bits?

> +        break;
> +    case R_RSTS:
> +        s->rsts = value;
> +        break;
> +    case R_WDOG:
> +        s->wdog = value;
> +        break;
> +
> +    default:
> +        qemu_log_mask(LOG_UNIMP,
> +                      "bcm2835_powermgt_write: Unknown offset %x\n",
> +                      (int)offset);

Please do not cast, use the proper format.

> +        break;
> +    }
> +}
> +
> +static const MemoryRegionOps bcm2835_powermgt_ops = {
> +    .read = bcm2835_powermgt_read,
> +    .write = bcm2835_powermgt_write,
> +    .endianness = DEVICE_NATIVE_ENDIAN,
> +};
> +
> +static const VMStateDescription vmstate_bcm2835_powermgt = {
> +    .name = TYPE_BCM2835_POWERMGT,
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT32(rstc, BCM2835PowerMgtState),
> +        VMSTATE_UINT32(rsts, BCM2835PowerMgtState),
> +        VMSTATE_UINT32(wdog, BCM2835PowerMgtState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static void bcm2835_powermgt_init(Object *obj)
> +{
> +    BCM2835PowerMgtState *s = BCM2835_POWERMGT(obj);
> +
> +    memory_region_init_io(&s->iomem, obj, &bcm2835_powermgt_ops, s,
> +                          TYPE_BCM2835_POWERMGT, 0x114);
> +    sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem);
> +}
> +
> +static void bcm2835_powermgt_reset(DeviceState *dev)
> +{
> +    BCM2835PowerMgtState *s = BCM2835_POWERMGT(dev);
> +
> +    s->rstc = 0x00000102;
> +    s->rsts = 0x00001000;
> +    s->wdog = 0x00000000;

Where these bits come from?

> +}
> +
> +static void bcm2835_powermgt_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +
> +    dc->reset = bcm2835_powermgt_reset;
> +    dc->vmsd = &vmstate_bcm2835_powermgt;
> +}
> +
> +static TypeInfo bcm2835_powermgt_info = {
> +    .name          = TYPE_BCM2835_POWERMGT,
> +    .parent        = TYPE_SYS_BUS_DEVICE,
> +    .instance_size = sizeof(BCM2835PowerMgtState),
> +    .class_init    = bcm2835_powermgt_class_init,
> +    .instance_init = bcm2835_powermgt_init,
> +};

Minor comments, otherwise:

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>