Re: [PATCH 04/14] hw/arm/raspi: add a skeleton implementation of the cprman

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

On 9/28/20 10:45 AM, Luc Michel wrote:
> On 23:05 Sat 26 Sep     , Philippe Mathieu-Daudé wrote:
>> On 9/25/20 12:17 PM, Luc Michel wrote:
>>> The BCM2835 cprman is the clock manager of the SoC. It is composed of a
>>
>> Can we use CPRMAN in caps?
>>
>>> main oscillator, and several sub-components (PLLs, multiplexers, ...) to
>>> generate the BCM2835 clock tree.
>>>
>>> This commit adds a skeleton of the cprman, with a dummy register
>>> read/write implementation. It embeds the main oscillator (xosc) from
>>> which all the clocks will be derived.
>>>
>>> Signed-off-by: Luc Michel <luc@lmichel.fr>
>>> ---
>>>  include/hw/arm/bcm2835_peripherals.h       |   3 +-
>>>  include/hw/misc/bcm2835_cprman.h           |  37 +++++
>>>  include/hw/misc/bcm2835_cprman_internals.h |  24 +++
>>>  hw/arm/bcm2835_peripherals.c               |  11 +-
>>>  hw/misc/bcm2835_cprman.c                   | 171 +++++++++++++++++++++
>>>  hw/misc/meson.build                        |   1 +
>>>  hw/misc/trace-events                       |   5 +
>>>  7 files changed, 250 insertions(+), 2 deletions(-)
>>>  create mode 100644 include/hw/misc/bcm2835_cprman.h
>>>  create mode 100644 include/hw/misc/bcm2835_cprman_internals.h
>>>  create mode 100644 hw/misc/bcm2835_cprman.c
>>>
>>> diff --git a/include/hw/arm/bcm2835_peripherals.h b/include/hw/arm/bcm2835_peripherals.h
>>> index 199088425a..002bb5e73b 100644
>>> --- a/include/hw/arm/bcm2835_peripherals.h
>>> +++ b/include/hw/arm/bcm2835_peripherals.h
>>> @@ -21,10 +21,11 @@
>>>  #include "hw/misc/bcm2835_property.h"
>>>  #include "hw/misc/bcm2835_rng.h"
>>>  #include "hw/misc/bcm2835_mbox.h"
>>>  #include "hw/misc/bcm2835_mphi.h"
>>>  #include "hw/misc/bcm2835_thermal.h"
>>> +#include "hw/misc/bcm2835_cprman.h"
>>>  #include "hw/sd/sdhci.h"
>>>  #include "hw/sd/bcm2835_sdhost.h"
>>>  #include "hw/gpio/bcm2835_gpio.h"
>>>  #include "hw/timer/bcm2835_systmr.h"
>>>  #include "hw/usb/hcd-dwc2.h"
>>> @@ -45,11 +46,11 @@ struct BCM2835PeripheralState {
>>>  
>>>      BCM2835SystemTimerState systmr;
>>>      BCM2835MphiState mphi;
>>>      UnimplementedDeviceState armtmr;
>>>      UnimplementedDeviceState powermgt;
>>> -    UnimplementedDeviceState cprman;
>>> +    BCM2835CprmanState cprman;
>>>      PL011State uart0;
>>>      BCM2835AuxState aux;
>>>      BCM2835FBState fb;
>>>      BCM2835DMAState dma;
>>>      BCM2835ICState ic;
>>> diff --git a/include/hw/misc/bcm2835_cprman.h b/include/hw/misc/bcm2835_cprman.h
>>> new file mode 100644
>>> index 0000000000..de9bd01b23
>>> --- /dev/null
>>> +++ b/include/hw/misc/bcm2835_cprman.h
>>> @@ -0,0 +1,37 @@
>>> +/*
>>> + * BCM2835 cprman clock manager
>>> + *
>>> + * Copyright (c) 2020 Luc Michel <luc@lmichel.fr>
>>> + *
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + */
>>> +
>>> +#ifndef HW_MISC_CPRMAN_H
>>> +#define HW_MISC_CPRMAN_H
>>> +
>>> +#include "hw/sysbus.h"
>>> +#include "hw/qdev-clock.h"
>>> +
>>> +#define TYPE_BCM2835_CPRMAN "bcm2835-cprman"
>>> +
>>> +typedef struct BCM2835CprmanState BCM2835CprmanState;
>>> +
>>> +DECLARE_INSTANCE_CHECKER(BCM2835CprmanState, CPRMAN,
>>> +                         TYPE_BCM2835_CPRMAN)
>>> +
>>> +#define CPRMAN_NUM_REGS (0x2000 / sizeof(uint32_t))
>>> +
>>> +struct BCM2835CprmanState {
>>> +    /*< private >*/
>>> +    SysBusDevice parent_obj;
>>> +
>>> +    /*< public >*/
>>> +    MemoryRegion iomem;
>>> +
>>> +    uint32_t regs[CPRMAN_NUM_REGS];
>>> +    uint32_t xosc_freq;
>>> +
>>> +    Clock *xosc;

Isn't it xosc external to the CPRMAN?

>>> +};
>>> +
>>> +#endif
>>> diff --git a/include/hw/misc/bcm2835_cprman_internals.h b/include/hw/misc/bcm2835_cprman_internals.h
>>> new file mode 100644
>>> index 0000000000..6a10b60930
>>> --- /dev/null
>>> +++ b/include/hw/misc/bcm2835_cprman_internals.h
>>> @@ -0,0 +1,24 @@
>>> +/*
>>> + * BCM2835 cprman clock manager
>>> + *
>>> + * Copyright (c) 2020 Luc Michel <luc@lmichel.fr>
>>> + *
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + */
>>> +
>>> +#ifndef HW_MISC_CPRMAN_INTERNALS_H
>>> +#define HW_MISC_CPRMAN_INTERNALS_H
>>> +
>>> +#include "hw/registerfields.h"
>>> +#include "hw/misc/bcm2835_cprman.h"
>>> +
>>> +/* Register map */
>>> +
>>> +/*
>>> + * This field is common to all registers. Each register write value must match
>>> + * the CPRMAN_PASSWORD magic value in its 8 MSB.
>>> + */
>>> +FIELD(CPRMAN, PASSWORD, 24, 8)
>>> +#define CPRMAN_PASSWORD 0x5a
>>
>> s/PASSWORD/KEY/?
> I'm not a big fan of this name either, but this is actually how this
> field is named in the datasheet and in various sources.
> 
> See:
>   - https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
>     (page 107)
>   - https://elinux.org/BCM2835_registers#CM (auto-generated from
>     Broadcom GPU related code)
>   - The Linux driver also use this name FWIW.

OK.

>>
>>> +
>>> +#endif
>>> diff --git a/hw/arm/bcm2835_peripherals.c b/hw/arm/bcm2835_peripherals.c
>>> index f0802c91e0..958aadeeb9 100644
>>> --- a/hw/arm/bcm2835_peripherals.c
>>> +++ b/hw/arm/bcm2835_peripherals.c
>>> @@ -119,10 +119,13 @@ static void bcm2835_peripherals_init(Object *obj)
>>>      object_initialize_child(obj, "mphi", &s->mphi, TYPE_BCM2835_MPHI);
>>>  
>>>      /* DWC2 */
>>>      object_initialize_child(obj, "dwc2", &s->dwc2, TYPE_DWC2_USB);
>>>  
>>> +    /* CPRMAN clock manager */
>>> +    object_initialize_child(obj, "cprman", &s->cprman, TYPE_BCM2835_CPRMAN);
>>> +
>>>      object_property_add_const_link(OBJECT(&s->dwc2), "dma-mr",
>>>                                     OBJECT(&s->gpu_bus_mr));
>>>  }
>>>  
>>>  static void bcm2835_peripherals_realize(DeviceState *dev, Error **errp)
>>> @@ -158,10 +161,17 @@ static void bcm2835_peripherals_realize(DeviceState *dev, Error **errp)
>>>      /* Interrupt Controller */
>>>      if (!sysbus_realize(SYS_BUS_DEVICE(&s->ic), errp)) {
>>>          return;
>>>      }
>>>  
>>> +    /* CPRMAN clock manager */
>>> +    if (!sysbus_realize(SYS_BUS_DEVICE(&s->cprman), errp)) {
>>> +        return;
>>> +    }
>>> +    memory_region_add_subregion(&s->peri_mr, CPRMAN_OFFSET,
>>> +                sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->cprman), 0));
>>> +
>>>      memory_region_add_subregion(&s->peri_mr, ARMCTRL_IC_OFFSET,
>>>                  sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->ic), 0));
>>>      sysbus_pass_irq(SYS_BUS_DEVICE(s), SYS_BUS_DEVICE(&s->ic));
>>>  
>>>      /* Sys Timer */
>>> @@ -343,11 +353,10 @@ static void bcm2835_peripherals_realize(DeviceState *dev, Error **errp)
>>>          qdev_get_gpio_in_named(DEVICE(&s->ic), BCM2835_IC_GPU_IRQ,
>>>                                 INTERRUPT_USB));
>>>  
>>>      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->cprman, "bcm2835-cprman", CPRMAN_OFFSET, 0x2000);
>>>      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);
>>>      create_unimp(s, &s->bscsl, "bcm2835-spis", BSC_SL_OFFSET, 0x100);
>>>      create_unimp(s, &s->i2c[0], "bcm2835-i2c0", BSC0_OFFSET, 0x20);
>>> diff --git a/hw/misc/bcm2835_cprman.c b/hw/misc/bcm2835_cprman.c
>>> new file mode 100644
>>> index 0000000000..d2ea0c9236
>>> --- /dev/null
>>> +++ b/hw/misc/bcm2835_cprman.c
>>> @@ -0,0 +1,171 @@
>>> +/*
>>> + * BCM2835 cprman clock manager
>>> + *
>>> + * Copyright (c) 2020 Luc Michel <luc@lmichel.fr>
>>> + *
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + */
>>> +
>>> +/*
>>> + * This peripheral is roughly divided into 3 main parts:
>>> + *   - the PLLs
>>> + *   - the PLL channels
>>> + *   - the clock muxes
>>> + *
>>> + * A main oscillator (xosc) feeds all the PLLs. Each PLLs has one or more
>>> + * channels. Those channel are then connected to the clock muxes. Each mux has
>>> + * multiples sources (usually the xosc, some of the PLL channels and some "test
>>> + * debug" clocks). It can selects one or the other through a control register.
>>
>> "It" is unclear (to me) in this sentence. Assuming the mux.
>>
>>> + * Each mux has one output clock that also goes out of the CPRMAN. It usually
>>
>> Here is "It" the mux or the output clock? Assuming the mux.
>>
>>> + * connects to another peripheral in the SoC (so a given mux is dedicated to a
>>> + * peripheral).
>>> + *
>>> + * At each level (PLL, channel and mux), the clock can be altered through
>>> + * dividers (and multipliers in case of the PLLs), and can be disabled (in this
>>> + * case, the next levels see no clock).
>>> + *
>>> + * This can be sum-up as follows (this is an example and not the actual BCM2835
>>> + * clock tree):
>>> + *
>>> + *          /-->[PLL]-|->[PLL channel]--...            [mux]--> to peripherals
>>> + *          |         |->[PLL channel]  muxes takes    [mux]
>>> + *          |         \->[PLL channel]  inputs from    [mux]
>>> + *          |                           some channels  [mux]
>>> + * [xosc]---|-->[PLL]-|->[PLL channel]  and other srcs [mux]
>>> + *          |         \->[PLL channel]           ...-->[mux]
>>> + *          |                                          [mux]
>>> + *          \-->[PLL]--->[PLL channel]                 [mux]
>>> + *
>>> + * The page at https://elinux.org/The_Undocumented_Pi gives the actual clock
>>> + * tree configuration.
>>> + */
>>> +
>>> +#include "qemu/osdep.h"
>>> +#include "qemu/log.h"
>>> +#include "migration/vmstate.h"
>>> +#include "hw/qdev-properties.h"
>>> +#include "hw/misc/bcm2835_cprman.h"
>>> +#include "hw/misc/bcm2835_cprman_internals.h"
>>> +#include "trace.h"
>>> +
>>> +/* CPRMAN "top level" model */
>>> +
>>> +static uint64_t cprman_read(void *opaque, hwaddr offset,
>>> +                                    unsigned size)
>>
>> Indent off.
>>
>>> +{
>>> +    BCM2835CprmanState *s = CPRMAN(opaque);
>>> +    uint64_t r = 0;
>>> +    size_t idx = offset / sizeof(uint32_t);
>>> +
>>> +    switch (idx) {
>>> +    default:
>>> +        r = s->regs[idx];
>>> +    }
>>> +
>>> +    trace_bcm2835_cprman_read(offset, r);
>>> +    return r;
>>> +}
>>> +
>>> +static void cprman_write(void *opaque, hwaddr offset,
>>> +                         uint64_t value, unsigned size)
>>> +{
>>> +    BCM2835CprmanState *s = CPRMAN(opaque);
>>> +    size_t idx = offset / sizeof(uint32_t);
>>> +
>>> +    if (FIELD_EX32(value, CPRMAN, PASSWORD) != CPRMAN_PASSWORD) {
>>> +        trace_bcm2835_cprman_write_invalid_magic(offset, value);
>>> +        return;
>>> +    }
>>> +
>>> +    value &= ~R_CPRMAN_PASSWORD_MASK;
>>> +
>>> +    trace_bcm2835_cprman_write(offset, value);
>>> +    s->regs[idx] = value;
>>> +
>>> +}
>>> +
>>> +static const MemoryRegionOps cprman_ops = {
>>> +    .read = cprman_read,
>>> +    .write = cprman_write,
>>> +    .endianness = DEVICE_LITTLE_ENDIAN,
>>> +    .valid      = {
>>> +        .min_access_size        = 4,
>>> +        .max_access_size        = 4,
>>
>> I couldn't find this in the public datasheets (any pointer?).
>>
>> Since your implementation is 32bit, can you explicit .impl
>> min/max = 4?
> 
> I could not find this information either, but I assumed this is the
> case, mainly because of the 'PASSWORD' field in all registers.

Good point. Do you mind adding a comment about it here please?

> 
> Regarding .impl, I thought that having .valid was enough?

Until we eventually figure out we can do 64-bit accesses,
so someone change .valid.max to 8 and your model is broken :/

> 
>>
>>> +        .unaligned              = false,
>>> +    },
>>> +};
>>> +
>>> +static void cprman_reset(DeviceState *dev)
>>> +{
>>> +    BCM2835CprmanState *s = CPRMAN(dev);
>>> +
>>> +    memset(s->regs, 0, sizeof(s->regs));
>>> +
>>> +    clock_update_hz(s->xosc, s->xosc_freq);
>>> +}
>>> +
>>> +static Clock *init_internal_clock(BCM2835CprmanState *s,
>>> +                                  const char *name)
>>
>> Interesting. Shouldn't this be a public function from the
>> Clock API? (Taking Object + name arguments)?
>>
> Yes, I hesitated to do just that. I'll add a patch for it when I re-roll.
>>> +{
>>> +    Object *obj;
>>> +    Clock *clk;
>>> +
>>> +    obj = object_new(TYPE_CLOCK);
>>> +    object_property_add_child(OBJECT(s), name, obj);
>>> +    object_unref(obj);
>>> +
>>> +    clk = CLOCK(obj);
>>> +    clock_setup_canonical_path(clk);
>>> +
>>> +    return clk;
>>> +}
>>> +
>>> +static void cprman_init(Object *obj)
>>> +{
>>> +    BCM2835CprmanState *s = CPRMAN(obj);
>>> +
>>> +    s->xosc = init_internal_clock(s, "xosc");
>>> +
>>> +    memory_region_init_io(&s->iomem, obj, &cprman_ops,
>>> +                          s, "bcm2835-cprman", 0x2000);
>>
>> Again assuming this is a 8KB MMIO device:
>>
>> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> 
> Thanks!
>