Re: [PATCH v2] accel/ivpu: Read preemption buffer size from boot params

["Wachowski, Karol" <karol.wachowski@linux.intel.com>]

On 28-Oct-26 16:22, Jeff Hugo wrote:
> On 10/28/2026 2:59 AM, Wachowski, Karol wrote:
>> On 27-Oct-26 17:45, Andrzej Kacprowski wrote:
>>> The optimal preemption buffer size depends on the hardware and firmware
>>> configuration, which is best known to the firmware. Newer firmware
>>> reports the required size in the preemption_buffer_size field of the
>>> boot params, which it writes before signaling cold boot completion.
>>>
>>> Read the size from the boot params once, after the initial cold boot
>>> during device initialization, as the firmware does not update it
>>> afterwards. Use it as the primary preemption buffer size and skip
>>> allocating the secondary buffer. A size outside of the [2 MiB, 32 MiB]
>>> range is treated as a firmware error and fails probe. If the firmware
>>> does not report the size, keep using the sizes from the firmware image
>>> header to preserve compatibility with older firmware.
>>>
>>> The preemption buffer sizes in the image header are deprecated in
>>> favor of the boot params, meaning the boot params size takes
>>> precedence when available. Firmware still provides valid sizes in the
>>> image header so that older kernels keep working, so the image header
>>> sizes are always validated and used until the boot params are read.
>>>
>>> Simplify the image header size selection: use the max sizes for both
>>> buffers when preemption_buffer_1_max_size is set, otherwise use the
>>> regular sizes. All known firmware versions that set
>>> preemption_buffer_1_max_size also set preemption_buffer_2_max_size, so
>>> selecting each buffer size separately is not needed.
>>>
>>> Move initialization of the trace and DVFS defaults to
>>> ivpu_fw_preboot_init().
>>>
>>> Update the FW boot API header to version 3.39.1:
>>> - Add the VPU_GOV_ON_DEMAND_PER_PRIORITY and VPU_GOV_ON_DEMAND_QOS
>>>    DVFS governors
>>> - Add the preemption_buffer_size field to struct vpu_boot_params
>>> - Mark the preemption buffer sizes in the image header as deprecated
>>>    in favor of preemption_buffer_size
>>>
>>> Signed-off-by: Andrzej Kacprowski <andrzej.kacprowski@linux.intel.com>
>>
>> Reviewed-by: Karol Wachowski <karol.wachowski@linux.intel.com>
> Reviewed-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>

Applied to drm-misc-next.