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

[Nolan <nolan@sigbus.net>]

On 5/31/21 4:23 AM, Philippe Mathieu-Daudé wrote:
> 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.

Ugh, oops. I was trying out sourcehut for this, and reflexively gave 
them a marker email. I'm pretty sure sourcehut won't sell my email 
address, so I'll just change it.

> 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).

Thanks, good point re: this being tuned to what Linux (and u-boot) do. 
Poking around a bit, it looks like 
"trusted-firmware-a"/"arm-trusted-firmware" uses the same method, as do 
a couple of bare-metal/hobby OSes. Couldn't immediately figure out what 
FreeBSD does.

I'm not sure I understand your point about FIRMWARE_NOTIFY_REBOOT, my 
understanding is that message is there to tell the GPU firmware that 
we're about to reboot, so it can do things like reload the PCIe USB 
chip's firmware. In my testing without the watchdog module loaded, my 
physical pi4 does not reboot, so it appears that sending 
FIRMWARE_NOTIFY_REBOOT is not enough on its own.

>> 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,

Will do.

>> +
>> +    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).

OK.

>> +    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.

OK.

>> +        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.

OK.

>> +                qemu_system_shutdown_request(SHUTDOWN_CAUSE_GUEST_SHUTDOWN);
>> +            } else {
>> +                qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
>> +            }
>> +        }
> 
> Shouldn't we log the unsupported bits?

I can add that, I didn't originally because the unsupported writes are 
expected.

>> +        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.

OK.

>> +        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?

 From my pi4. https://elinux.org/BCM2835_registers agrees (processed 
from Broadcom source code).

>> +}
>> +
>> +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>
> 

I'll make the changes and send a v2.

- nolan