Re: [RFC v6 2/4] hw/misc: Introduce iommu-testdev for bare-metal IOMMU testing

[Fabiano Rosas <farosas@suse.de>]

Tao Tang <tangtao1634@phytium.com.cn> writes:

> Add a minimal PCI test device designed to exercise IOMMU translation
> (such as ARM SMMUv3) without requiring guest firmware or OS. The device
> provides MMIO registers to configure and trigger DMA operations with
> controllable attributes (security state, address space), enabling
> deterministic IOMMU testing.
>
> Key features:
> - Bare-metal IOMMU testing via simple MMIO interface
> - Configurable DMA attributes for security states and address spaces
> - Write-then-read verification pattern with automatic result checking
>
> The device performs a deterministic DMA test pattern: write a known
> value (0x88888888) to a configured IOVA, read it back, and verify data
> integrity. Results are reported through a dedicated result register,
> eliminating the need for complex interrupt handling or driver
> infrastructure in tests.
>
> This is purely a test device and not intended for production use or
> machine realism. It complements existing test infrastructure like
> pci-testdev but focuses specifically on IOMMU translation path
> validation.
>
> Signed-off-by: Tao Tang <tangtao1634@phytium.com.cn>
> Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
> ---
>  docs/specs/index.rst            |   1 +
>  docs/specs/iommu-testdev.rst    | 109 +++++++++++++
>  hw/misc/Kconfig                 |   5 +
>  hw/misc/iommu-testdev.c         | 278 ++++++++++++++++++++++++++++++++
>  hw/misc/meson.build             |   1 +
>  hw/misc/trace-events            |  10 ++
>  include/hw/misc/iommu-testdev.h |  70 ++++++++
>  7 files changed, 474 insertions(+)
>  create mode 100644 docs/specs/iommu-testdev.rst
>  create mode 100644 hw/misc/iommu-testdev.c
>  create mode 100644 include/hw/misc/iommu-testdev.h
>
> diff --git a/docs/specs/index.rst b/docs/specs/index.rst
> index f19d73c9f6..1fc7fae6bb 100644
> --- a/docs/specs/index.rst
> +++ b/docs/specs/index.rst
> @@ -39,3 +39,4 @@ guest hardware that is specific to QEMU.
>     riscv-iommu
>     riscv-aia
>     aspeed-intc
> +   iommu-testdev
> \ No newline at end of file
> diff --git a/docs/specs/iommu-testdev.rst b/docs/specs/iommu-testdev.rst
> new file mode 100644
> index 0000000000..fdc7f2ee89
> --- /dev/null
> +++ b/docs/specs/iommu-testdev.rst
> @@ -0,0 +1,109 @@
> +iommu-testdev — IOMMU test device for bare-metal testing
> +=========================================================
> +
> +Overview
> +--------
> +``iommu-testdev`` is a minimal, test-only PCI device designed to exercise
> +IOMMU translation (such as ARM SMMUv3) without requiring firmware or a guest
> +OS. Tests can populate IOMMU translation tables with known values and trigger
> +DMA operations that flow through the IOMMU translation path. It is **not** a
> +faithful PCIe endpoint and must be considered a QEMU-internal test vehicle.
> +
> +Key Features
> +------------
> +* **Bare-metal IOMMU testing**: No guest kernel or firmware required
> +* **Configurable DMA attributes**: Supports address space  configuration via
> +  MMIO registers
> +* **Deterministic verification**: Write-then-read DMA pattern with automatic
> +  result checking
> +
> +Status
> +------
> +* Location: ``hw/misc/iommu-testdev.c``
> +* Header: ``include/hw/misc/iommu-testdev.h``
> +* Build guard: ``CONFIG_IOMMU_TESTDEV``
> +
> +Device Interface
> +----------------
> +The device exposes a single PCI BAR0 with MMIO registers:
> +
> +* ``ITD_REG_DMA_TRIGGERING`` (0x00): Reading triggers DMA execution
> +* ``ITD_REG_DMA_GVA_LO`` (0x04): IOVA/GVA bits [31:0]
> +* ``ITD_REG_DMA_GVA_HI`` (0x08): IOVA/GVA bits [63:32]
> +* ``ITD_REG_DMA_LEN`` (0x0C): DMA transfer length
> +* ``ITD_REG_DMA_RESULT`` (0x10): DMA operation result (0=success)
> +* ``ITD_REG_DMA_DBELL`` (0x14): Write 1 to arm DMA
> +* ``ITD_REG_DMA_ATTRS`` (0x18): DMA attributes
> +
> +  - bit[0]: secure (1=Secure, 0=Non-Secure)
> +  - bits[2:1]: address space (0=Non-Secure, 1=Secure, 2=Root, 3=Realm)
> +    Only these MemTxAttrs fields (``secure`` and ``space``) are consumed today;
> +    other bits are reserved but can be wired up easily if future tests need
> +    to pass extra attributes.
> +
> +Translation Setup Workflow
> +--------------------------
> +``iommu-testdev`` never builds SMMU/AMD-Vi/RISC-V IOMMU structures on its own.
> +Architecture-specific construction lives entirely in qtest/libqos helpers.
> +Those helpers populate guest memory with page tables/architecture-specific
> +structures and program the emulated IOMMU registers directly. See the
> +``qsmmu_setup_and_enable_translation()`` function in
> +``tests/qtest/libqos/qos-smmuv3.c`` for an example of how SMMUv3 translation
> +is set up for this device.
> +
> +DMA Operation Flow
> +------------------
> +1. Test programs IOMMU translation tables
> +2. Test configures DMA address (GVA_LO/HI), length, and attributes
> +3. Test writes 1 to DMA_DBELL to arm the operation
> +4. Test reads DMA_TRIGGERING to execute DMA
> +5. Test polls DMA_RESULT:
> +
> +   - 0x00000000: Success
> +   - 0xFFFFFFFE: Busy (still in progress)
> +   - 0xDEAD000X: Various error codes
> +
> +The device performs a write-then-read sequence using a known pattern
> +(0x88888888) and verifies data integrity automatically.
> +
> +Running the qtest
> +-----------------
> +The SMMUv3 test suite uses this device and covers multiple translation modes::
> +
> +    cd build-debug
> +    QTEST_QEMU_BINARY=./qemu-system-aarch64 \\
> +        ./tests/qtest/iommu-smmuv3-test --tap -k
> +
> +This test suite exercises:
> +
> +* Stage 1 only translation
> +* Stage 2 only translation
> +* Nested (Stage 1 + Stage 2) translation
> +* Multiple security spaces (Non-Secure, Secure, Root, Realm)
> +
> +Instantiation
> +-------------
> +The device is not wired into any board by default. Tests instantiate it
> +via QEMU command line::
> +
> +    -device iommu-testdev
> +
> +For ARM platforms with SMMUv3::
> +
> +    -M virt,iommu=smmuv3 -device iommu-testdev
> +
> +The device will be placed behind the IOMMU automatically.
> +
> +Limitations
> +-----------
> +* No realistic PCIe enumeration, MSI/MSI-X, or interrupt handling
> +* No ATS/PRI support
> +* No actual device functionality beyond DMA test pattern
> +* Test-only; not suitable for production or machine realism
> +* Address space support (Secure/Root/Realm) is architecture-dependent
> +
> +See also
> +--------
> +* ``tests/qtest/iommu-smmuv3-test.c`` — SMMUv3 test suite
> +* ``tests/qtest/libqos/qos-smmuv3.{c,h}`` — SMMUv3 test library
> +* SMMUv3 emulation: ``hw/arm/smmu*``
> diff --git a/hw/misc/Kconfig b/hw/misc/Kconfig
> index fccd735c24..b5f6fdbd9c 100644
> --- a/hw/misc/Kconfig
> +++ b/hw/misc/Kconfig
> @@ -25,6 +25,11 @@ config PCI_TESTDEV
>      default y if TEST_DEVICES
>      depends on PCI
>  
> +config IOMMU_TESTDEV
> +    bool
> +    default y if TEST_DEVICES
> +    depends on PCI
> +
>  config EDU
>      bool
>      default y if TEST_DEVICES
> diff --git a/hw/misc/iommu-testdev.c b/hw/misc/iommu-testdev.c
> new file mode 100644
> index 0000000000..3182ccea4d
> --- /dev/null
> +++ b/hw/misc/iommu-testdev.c
> @@ -0,0 +1,278 @@
> +/*
> + * A test device for IOMMU
> + *
> + * This test device is a minimal IOMMU-aware device used to test the IOMMU.
> + *
> + * Copyright (c) 2025 Phytium Technology
> + *
> + * Author:
> + *  Tao Tang <tangtao1634@phytium.com.cn>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "system/address-spaces.h"
> +#include "trace.h"
> +#include "hw/pci/pci_device.h"
> +#include "hw/qdev-properties.h"
> +#include "qom/object.h"
> +#include "hw/misc/iommu-testdev.h"
> +
> +#define TYPE_IOMMU_TESTDEV "iommu-testdev"
> +OBJECT_DECLARE_SIMPLE_TYPE(IOMMUTestDevState, IOMMU_TESTDEV)
> +
> +struct IOMMUTestDevState {
> +    PCIDevice parent_obj;
> +    MemoryRegion bar0;
> +    uint64_t dma_vaddr;
> +    uint32_t dma_len;
> +    uint32_t dma_result;
> +    bool dma_pending;
> +
> +    AddressSpace *dma_as;   /* IOMMU-mediated DMA AS for this device */
> +    uint32_t dma_attrs_cfg; /* bit0 secure, bits[2:1] space, bit3 unspecified */
> +};
> +
> +static void iommu_testdev_maybe_run_dma(IOMMUTestDevState *s)
> +{
> +    uint32_t expected_val, actual_val;
> +    g_autofree uint8_t *write_buf = NULL;
> +    g_autofree uint8_t *read_buf = NULL;
> +    MemTxResult write_res, read_res;
> +    MemTxAttrs attrs;
> +    AddressSpace *as;
> +
> +    if (!s->dma_pending) {
> +        s->dma_result = ITD_DMA_ERR_NOT_ARMED;
> +        trace_iommu_testdev_dma_result(s->dma_result);
> +        return;
> +    }
> +    trace_iommu_testdev_dma_start();
> +
> +    s->dma_pending = false;
> +
> +    if (!s->dma_len) {
> +        s->dma_result = ITD_DMA_ERR_BAD_LEN;
> +        return;
> +    }
> +
> +    write_buf = g_malloc(s->dma_len);
> +    read_buf = g_malloc(s->dma_len);
> +
> +    /* Initialize MemTxAttrs from generic register */
> +    attrs = MEMTXATTRS_UNSPECIFIED;
> +    attrs.secure = ITD_ATTRS_GET_SECURE(s->dma_attrs_cfg);
> +
> +    /*
> +     * The 'space' field in MemTxAttrs is ARM-specific.
> +     * On other architectures where this field doesn't exist.
> +     */
> +    attrs.space = ITD_ATTRS_GET_SPACE(s->dma_attrs_cfg);
> +
> +    as = s->dma_as;
> +
> +    /* Step 1: Write ITD_DMA_WRITE_VAL to DMA address */
> +    trace_iommu_testdev_dma_write(s->dma_vaddr, s->dma_len);
> +
> +    for (int i = 0; i < s->dma_len; i++) {
> +        /* Data is written in little-endian order */
> +        write_buf[i] = (ITD_DMA_WRITE_VAL >> ((i % 4) * 8)) & 0xff;
> +    }
> +    write_res = dma_memory_write(as, s->dma_vaddr, write_buf, s->dma_len,
> +                                 attrs);
> +
> +    if (write_res != MEMTX_OK) {
> +        s->dma_result = ITD_DMA_ERR_TX_FAIL;
> +        trace_iommu_testdev_dma_result(s->dma_result);
> +        return;
> +    }
> +
> +    /* Step 2: Read back from the same DMA address */
> +    trace_iommu_testdev_dma_read(s->dma_vaddr, s->dma_len);
> +
> +    read_res = dma_memory_read(as, s->dma_vaddr, read_buf, s->dma_len, attrs);
> +
> +    if (read_res != MEMTX_OK) {
> +        s->dma_result = ITD_DMA_ERR_RD_FAIL;
> +        trace_iommu_testdev_dma_result(s->dma_result);
> +        return;
> +    }
> +
> +    /* Step 3: Verify the read data matches what we wrote */
> +    for (int i = 0; i < s->dma_len; i += 4) {
> +        int remaining_bytes = MIN(4, s->dma_len - i);
> +
> +        expected_val = 0;
> +        actual_val = 0;
> +
> +        for (int j = 0; j < remaining_bytes; j++) {
> +            expected_val |= ((uint32_t)write_buf[i + j]) << (j * 8);
> +            actual_val |= ((uint32_t)read_buf[i + j]) << (j * 8);
> +        }
> +
> +        trace_iommu_testdev_dma_verify(expected_val, actual_val);
> +
> +        if (expected_val != actual_val) {
> +            s->dma_result = ITD_DMA_ERR_MISMATCH;
> +            trace_iommu_testdev_dma_result(s->dma_result);
> +            return;
> +        }
> +    }
> +
> +    /* All checks passed */
> +    s->dma_result = 0;
> +    trace_iommu_testdev_dma_result(s->dma_result);
> +}
> +
> +static uint64_t iommu_testdev_mmio_read(void *opaque, hwaddr addr,
> +                                        unsigned size)
> +{
> +    IOMMUTestDevState *s = opaque;
> +    uint64_t value = 0;
> +
> +    switch (addr) {
> +    case ITD_REG_DMA_TRIGGERING:
> +        /*
> +         * This lets tests poll ITD_REG_DMA_RESULT to observe BUSY before
> +         * consuming the DMA.
> +         */
> +        iommu_testdev_maybe_run_dma(s);
> +        value = 0;
> +        break;
> +    case ITD_REG_DMA_GVA_LO:
> +        value = (uint32_t)(s->dma_vaddr & 0xffffffffu);
> +        break;
> +    case ITD_REG_DMA_GVA_HI:
> +        value = (uint32_t)(s->dma_vaddr >> 32);
> +        break;
> +    case ITD_REG_DMA_LEN:
> +        value = s->dma_len;
> +        break;
> +    case ITD_REG_DMA_RESULT:
> +        value = s->dma_result;
> +        break;
> +    case ITD_REG_DMA_ATTRS:
> +        value = s->dma_attrs_cfg;
> +        break;
> +    default:
> +        value = 0;
> +        break;
> +    }
> +
> +    trace_iommu_testdev_mmio_read(addr, value, size);
> +    return value;
> +}
> +
> +static void iommu_testdev_mmio_write(void *opaque, hwaddr addr, uint64_t val,
> +                                     unsigned size)
> +{
> +    IOMMUTestDevState *s = opaque;
> +    uint32_t data = val;
> +
> +    trace_iommu_testdev_mmio_write(addr, val, size);
> +
> +    switch (addr) {
> +    case ITD_REG_DMA_GVA_LO:
> +        s->dma_vaddr = (s->dma_vaddr & ~0xffffffffull) | data;
> +        break;
> +    case ITD_REG_DMA_GVA_HI:
> +        s->dma_vaddr = (s->dma_vaddr & 0xffffffffull) |
> +                       ((uint64_t)data << 32);
> +        break;
> +    case ITD_REG_DMA_LEN:
> +        s->dma_len = data;
> +        break;
> +    case ITD_REG_DMA_RESULT:
> +        s->dma_result = data;
> +        break;
> +    case ITD_REG_DMA_DBELL:
> +        if (data & ITD_DMA_DBELL_ARM) {
> +            /* Arm the DMA operation */
> +            s->dma_pending = true;
> +            s->dma_result = ITD_DMA_RESULT_BUSY;
> +            trace_iommu_testdev_dma_pending(true);
> +        } else {
> +            /* Disarm the DMA operation */
> +            s->dma_pending = false;
> +            s->dma_result = ITD_DMA_RESULT_IDLE;
> +            trace_iommu_testdev_dma_pending(false);
> +        }
> +        break;
> +    case ITD_REG_DMA_ATTRS:
> +        s->dma_attrs_cfg = data;
> +        break;
> +    default:
> +        break;
> +    }
> +}
> +
> +static const MemoryRegionOps iommu_testdev_mmio_ops = {
> +    .read = iommu_testdev_mmio_read,
> +    .write = iommu_testdev_mmio_write,
> +    .endianness = DEVICE_LITTLE_ENDIAN,
> +    .valid = {
> +        .min_access_size = 4,
> +        .max_access_size = 4,
> +    },
> +};
> +
> +static void iommu_testdev_realize(PCIDevice *pdev, Error **errp)
> +{
> +    IOMMUTestDevState *s = IOMMU_TESTDEV(pdev);
> +
> +    s->dma_vaddr = 0;
> +    s->dma_len = 0;
> +    s->dma_result = ITD_DMA_RESULT_IDLE;
> +    s->dma_pending = false;
> +    s->dma_attrs_cfg = 0;
> +    s->dma_as = pci_device_iommu_address_space(pdev);
> +
> +    memory_region_init_io(&s->bar0, OBJECT(pdev), &iommu_testdev_mmio_ops, s,
> +                          TYPE_IOMMU_TESTDEV ".bar0", BAR0_SIZE);
> +    pci_register_bar(pdev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY, &s->bar0);
> +}
> +
> +static void iommu_testdev_reset(DeviceState *dev)
> +{
> +    IOMMUTestDevState *s = IOMMU_TESTDEV(dev);
> +
> +    s->dma_vaddr = 0;
> +    s->dma_len = 0;
> +    s->dma_result = ITD_DMA_RESULT_IDLE;
> +    s->dma_pending = false;
> +    s->dma_attrs_cfg = 0;
> +}
> +
> +static void iommu_testdev_class_init(ObjectClass *klass, const void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    PCIDeviceClass *pc = PCI_DEVICE_CLASS(klass);
> +
> +    pc->realize = iommu_testdev_realize;
> +    pc->vendor_id = IOMMU_TESTDEV_VENDOR_ID;
> +    pc->device_id = IOMMU_TESTDEV_DEVICE_ID;
> +    pc->revision = 0;
> +    pc->class_id = PCI_CLASS_OTHERS;
> +    dc->desc = "A test device for IOMMU";
> +    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
> +    device_class_set_legacy_reset(dc, iommu_testdev_reset);
> +}
> +
> +static const TypeInfo iommu_testdev_info = {
> +    .name          = TYPE_IOMMU_TESTDEV,
> +    .parent        = TYPE_PCI_DEVICE,
> +    .instance_size = sizeof(IOMMUTestDevState),
> +    .class_init    = iommu_testdev_class_init,
> +    .interfaces    = (const InterfaceInfo[]) {
> +        { INTERFACE_CONVENTIONAL_PCI_DEVICE },
> +        { }
> +    },
> +};
> +
> +static void iommu_testdev_register_types(void)
> +{
> +    type_register_static(&iommu_testdev_info);
> +}
> +
> +type_init(iommu_testdev_register_types);
> diff --git a/hw/misc/meson.build b/hw/misc/meson.build
> index b1d8d8e5d2..6f9bb9bb0f 100644
> --- a/hw/misc/meson.build
> +++ b/hw/misc/meson.build
> @@ -4,6 +4,7 @@ system_ss.add(when: 'CONFIG_FW_CFG_DMA', if_true: files('vmcoreinfo.c'))
>  system_ss.add(when: 'CONFIG_ISA_DEBUG', if_true: files('debugexit.c'))
>  system_ss.add(when: 'CONFIG_ISA_TESTDEV', if_true: files('pc-testdev.c'))
>  system_ss.add(when: 'CONFIG_PCI_TESTDEV', if_true: files('pci-testdev.c'))
> +system_ss.add(when: 'CONFIG_IOMMU_TESTDEV', if_true: files('iommu-testdev.c'))
>  system_ss.add(when: 'CONFIG_UNIMP', if_true: files('unimp.c'))
>  system_ss.add(when: 'CONFIG_EMPTY_SLOT', if_true: files('empty_slot.c'))
>  system_ss.add(when: 'CONFIG_LED', if_true: files('led.c'))
> diff --git a/hw/misc/trace-events b/hw/misc/trace-events
> index eeb9243898..84fd349fb8 100644
> --- a/hw/misc/trace-events
> +++ b/hw/misc/trace-events
> @@ -409,3 +409,13 @@ ivshmem_flat_interrupt_peer(uint16_t peer_id, uint16_t vector_id) "Interrupting
>  i2c_echo_event(const char *id, const char *event) "%s: %s"
>  i2c_echo_recv(const char *id, uint8_t data) "%s: recv 0x%02" PRIx8
>  i2c_echo_send(const char *id, uint8_t data) "%s: send 0x%02" PRIx8
> +
> +# iommu-testdev.c
> +iommu_testdev_mmio_read(uint64_t addr, uint64_t value, unsigned size) "addr=0x%" PRIx64 " value=0x%" PRIx64 " size=%u"
> +iommu_testdev_mmio_write(uint64_t addr, uint64_t value, unsigned size) "addr=0x%" PRIx64 " value=0x%" PRIx64 " size=%u"
> +iommu_testdev_dma_start(void) "DMA operation started"
> +iommu_testdev_dma_write(uint64_t gva, uint32_t len) "gva=0x%" PRIx64 " len=%u"
> +iommu_testdev_dma_read(uint64_t gva, uint32_t len) "gva=0x%" PRIx64 " len=%u"
> +iommu_testdev_dma_verify(uint32_t expected, uint32_t actual) "expected=0x%x actual=0x%x"
> +iommu_testdev_dma_result(uint32_t result) "DMA completed result=0x%x"
> +iommu_testdev_dma_pending(bool pending) "pending=%d"
> diff --git a/include/hw/misc/iommu-testdev.h b/include/hw/misc/iommu-testdev.h
> new file mode 100644
> index 0000000000..06924e737c
> --- /dev/null
> +++ b/include/hw/misc/iommu-testdev.h
> @@ -0,0 +1,70 @@
> +/*
> + * A test device for IOMMU
> + *
> + * This test device is a minimal IOMMU-aware device used to test the IOMMU.
> + *
> + * Copyright (c) 2025 Phytium Technology
> + *
> + * Author:
> + *  Tao Tang <tangtao1634@phytium.com.cn>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef HW_MISC_IOMMU_TESTDEV_H
> +#define HW_MISC_IOMMU_TESTDEV_H
> +
> +#include "hw/pci/pci.h"
> +
> +#define IOMMU_TESTDEV_VENDOR_ID     PCI_VENDOR_ID_REDHAT
> +#define IOMMU_TESTDEV_DEVICE_ID     PCI_DEVICE_ID_REDHAT_TEST
> +
> +/* DMA_ATTRS register bit definitions (architecture-agnostic) */
> +#define ITD_ATTRS_SECURE_SHIFT      0
> +#define ITD_ATTRS_SECURE_MASK       0x1
> +#define ITD_ATTRS_SPACE_SHIFT       1
> +#define ITD_ATTRS_SPACE_MASK        0x3
> +
> +/* Helper macros for setting fields */
> +#define ITD_ATTRS_SET_SECURE(attrs, val)                              \
> +    (((attrs) & ~(ITD_ATTRS_SECURE_MASK << ITD_ATTRS_SECURE_SHIFT)) | \
> +     (((val) & ITD_ATTRS_SECURE_MASK) << ITD_ATTRS_SECURE_SHIFT))
> +
> +#define ITD_ATTRS_SET_SPACE(attrs, val)                               \
> +    (((attrs) & ~(ITD_ATTRS_SPACE_MASK << ITD_ATTRS_SPACE_SHIFT)) |   \
> +     (((val) & ITD_ATTRS_SPACE_MASK) << ITD_ATTRS_SPACE_SHIFT))
> +
> +/* Helper macros for getting fields */
> +#define ITD_ATTRS_GET_SECURE(attrs)                                   \
> +    (((attrs) >> ITD_ATTRS_SECURE_SHIFT) & ITD_ATTRS_SECURE_MASK)
> +
> +#define ITD_ATTRS_GET_SPACE(attrs)                                    \
> +    (((attrs) >> ITD_ATTRS_SPACE_SHIFT) & ITD_ATTRS_SPACE_MASK)
> +
> +/* DMA result/status values shared with tests */
> +#define ITD_DMA_RESULT_IDLE   0xffffffffu
> +#define ITD_DMA_RESULT_BUSY   0xfffffffeu
> +#define ITD_DMA_ERR_BAD_LEN   0xdead0001u
> +#define ITD_DMA_ERR_TX_FAIL   0xdead0002u
> +#define ITD_DMA_ERR_RD_FAIL   0xdead0003u
> +#define ITD_DMA_ERR_MISMATCH  0xdead0004u
> +#define ITD_DMA_ERR_NOT_ARMED 0xdead0005u
> +
> +#define ITD_DMA_WRITE_VAL     0x88888888u

Is this intended to read the same regardless of endianness? It would
mask possible endianness bugs.

For the rest of the patch:

Reviewed-by: Fabiano Rosas <farosas@suse.de>