Re: [PATCH 3/3] hw/cxl: Add Physical Port Control (Opcode 5102h)

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Mon,  2 Jun 2025 19:29:42 +0530
Arpit Kumar <arpit1.kumar@samsung.com> wrote:


Very interesting to see support for this. It will enable a load
of additional test cases.

> added assert-deassert PERST implementation, reset PPB
> for physical port.
Added

Please also include some details of testing done and what happens.
Given I know we have some issues with reset that we haven't resolved
I'm curious if you see them here.

> 
> Signed-off-by: Arpit Kumar <arpit1.kumar@samsung.com>

> +/* Assert - Deassert PERST */
> +#define ASSERT_WAIT_TIME_MS 100
> +
>  /* link state flags */
>  #define LINK_STATE_FLAG_LANE_REVERSED    (1 << 0)
>  #define LINK_STATE_FLAG_PERST_ASSERTED   (1 << 1)
> @@ -662,6 +666,114 @@ static CXLRetCode cmd_get_physical_port_state(const struct cxl_cmd *cmd,
>      return CXL_MBOX_SUCCESS;
>  }
>  
> +static struct PCIDevice *cxl_find_port_dev(uint8_t ppb_id, PCIBus *bus)
> +{
> +    PCIDevice *d;
> +    int devfn;
> +
> +    for (devfn = 0; devfn < ARRAY_SIZE(bus->devices); devfn++) {

As in patch one, maybe use the for_each_pci_...  Though with the callback
needed it may end up slightly more complex that this.


> +        d = bus->devices[devfn];
> +        if (d) {
> +            if (object_dynamic_cast(OBJECT(d), TYPE_CXL_DSP)) {
> +                uint8_t port = PCIE_PORT(d)->port;
I'd not bother with the local variable for this one.

                 if (PCIE_PORT(d)->port == ppb_id) {
                     return d;
                 }

> +                if (port == ppb_id) {
> +                    return d;
> +                }
> +            }
> +        }
> +    }
> +    return NULL;
> +}
> +
> +static CXLRetCode deassert_PERST(Object *obj, ResetType type, uint8_t pn, CXLCCI *cci)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +
> +    if (cci->pports.perst[pn].issued_assert_PERST) {
> +        if (cci->pports.perst[pn].asrt_time == -1 && !s->hold_phase_pending) {

I'd flip the logic as then can return early in error case and reduce
indent of the rest.


> +            qemu_mutex_lock(&cci->pports.perst[pn].lock);

            QEMU_LOCK_GUARD(&cci->pports.prst[pn].lock);

> +            resettable_release_reset(obj, type);
> +            cci->pports.perst[pn].issued_assert_PERST = false;
> +            cci->pports.pport_info[pn].link_state_flags &=
> +                ~LINK_STATE_FLAG_PERST_ASSERTED;
> +            cci->pports.perst[pn].asrt_time = ASSERT_WAIT_TIME_MS;
> +            qemu_mutex_unlock(&cci->pports.perst[pn].lock);
and drop explicit unlock.
> +        } else {
> +            return CXL_MBOX_INTERNAL_ERROR;
> +        }
> +    } else {
> +        return CXL_MBOX_INTERNAL_ERROR;
> +    }
> +    return CXL_MBOX_SUCCESS;
> +}
> +
> +static CXLRetCode assert_PERST(Object *obj, ResetType type, uint8_t pn, CXLCCI *cci)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +
> +    if (cci->pports.perst[pn].issued_assert_PERST || s->exit_phase_in_progress) {
> +        return CXL_MBOX_INTERNAL_ERROR;
> +    }
> +

WITH_QEMU_LOCK_GUARD() perhaps

> +    qemu_mutex_lock(&cci->pports.perst[pn].lock);
> +    cci->pports.perst[pn].issued_assert_PERST = true;
> +    cci->pports.pport_info[pn].link_state_flags |=
> +        LINK_STATE_FLAG_PERST_ASSERTED;
> +    resettable_assert_reset(obj, type);
> +    qemu_mutex_unlock(&cci->pports.perst[pn].lock);
> +
> +    /* holding reset phase for 100ms */
> +    while (cci->pports.perst[pn].asrt_time--) {
> +        usleep(1000);
Is this happening synchronously?  I'd kind of expect it to be a background thing
where we'd just check it had finished.
> +    }
> +    return CXL_MBOX_SUCCESS;
> +}
> +
> +/*CXL r3.2 Section 7.6.7.1.3: Get Physical Port Control (Opcode 5102h)*/
> +static CXLRetCode cmd_physical_port_control(const struct cxl_cmd *cmd,
> +                                            uint8_t *payload_in,
> +                                            size_t len_in,
> +                                            uint8_t *payload_out,
> +                                            size_t *len_out,
> +                                            CXLCCI *cci)
> +{
> +    PCIBus *bus = &PCI_BRIDGE(cci->d)->sec_bus;
> +    PCIDevice *dev;
> +    struct cxl_fmapi_get_physical_port_control_req_pl {
> +        uint8_t PPB_ID;
> +        uint8_t Ports_Op;
> +    } QEMU_PACKED *in;
> +
> +    in = (struct cxl_fmapi_get_physical_port_control_req_pl *)payload_in;

Often we cheat on these where the type is locally defined and do

    struct cxl_fmapi_get_physical_port_control_req_pl {
        uint8_t ppb_id;
        uint8_t ports_op;
    } QEMU_PACKED *in = (void *)payload_in;

Given it's all together the type isn't confusing or ambiguous even
though we use a void * instead of the more specific cast.

Note also that it is better to stick to local style and use lower_case
style for structure element naming etc.

> +
> +    if (len_in < sizeof(*in)) {
> +        return CXL_MBOX_INVALID_PAYLOAD_LENGTH;
> +    }
> +
> +    uint8_t pn = in->PPB_ID;
> +    dev = cxl_find_port_dev(pn, bus);
> +    if (!dev) {
> +        return CXL_MBOX_INTERNAL_ERROR;
> +    }
> +
> +    switch (in->Ports_Op) {
> +    case 0:
> +        assert_PERST(OBJECT(&dev->qdev), RESET_TYPE_COLD, pn, cci);

Even for these probably

assert_perst()

> +        break;
return CXL_MBOX_SUCESS;
> +    case 1:
> +        deassert_PERST(OBJECT(&dev->qdev), RESET_TYPE_COLD, pn, cci);
> +        break;
> +    case 2:
> +        device_cold_reset(&dev->qdev);
> +        break;
> +    default:
> +        return CXL_MBOX_INVALID_INPUT;
> +    }
> +    return CXL_MBOX_SUCCESS;
> +}
> +

> @@ -3878,4 +3995,15 @@ void cxl_initialize_usp_mctpcci(CXLCCI *cci, DeviceState *d, DeviceState *intf,
>      cci->intf = intf;
>      cxl_init_cci(cci, payload_max);
>      cxl_set_phy_port_info(cci); /* store port info */
> +    /* physical port control */
> +    for (int i = 0; i < PCI_DEVFN_MAX; i++) {
> +        qemu_mutex_init(&cci->pports.perst[i].lock);

perst is definitely port wise - not linked to CCI so that stuff should be
in the port structures themselves.

> +        cci->pports.perst[i].issued_assert_PERST = false;
> +        /* Assert PERST involves physical port to be in
wrap at 80 chars.
> +         * hold reset phase for minimum 100ms. No other calls
> +         * are entertained until Deassert PERST command.
> +         * https://patchwork.ozlabs.org/project/linux-pci/patch/20190523194409.17718-1-niklas.cassel@linaro.org/#2178369

Blocking other commands is fine but we should lock up emulation of other stuff
in the system and I think you currently do.

> +         */
> +        cci->pports.perst[i].asrt_time = ASSERT_WAIT_TIME_MS;
> +    }
>  }
> diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> index 9eb128a1e8..f877d60b39 100644
> --- a/include/hw/cxl/cxl_device.h
> +++ b/include/hw/cxl/cxl_device.h
> @@ -146,10 +146,18 @@ struct cxl_phy_port_info {
>      uint8_t supported_ld_count;
>  } QEMU_PACKED;
>  
> +/* assert-deassert PERST */
> +struct pperst {
> +    bool issued_assert_PERST;
> +    int asrt_time;
> +    QemuMutex lock;
> +};
> +
>  struct phy_port {
>      uint8_t num_ports;
>      uint8_t active_port_bitmask[0x20];
>      struct cxl_phy_port_info pport_info[PCI_DEVFN_MAX];
> +    struct pperst perst[PCI_DEVFN_MAX];
>  };
>  
>  /* CXL r3.1 Table 8-34: Command Return Codes */