Re: [PATCH v10 08/28] gpu: nova-core: Blackwell: calculate reserved FB heap size

[John Hubbard]

On 4/17/26 7:23 AM, Alexandre Courbot wrote:
> On Sat Apr 11, 2026 at 11:49 AM JST, John Hubbard wrote:
> <snip>
>> @@ -168,6 +175,8 @@ pub(crate) struct FbLayout {
>>      pub(crate) wpr2: FbRange,
>>      pub(crate) heap: FbRange,
>>      pub(crate) vf_partition_count: u8,
>> +    /// PMU reserved memory size, in bytes.
>> +    pub(crate) pmu_reserved_size: u32,
>>  }
>>  
>>  impl FbLayout {
>> @@ -268,6 +277,29 @@ pub(crate) fn new(chipset: Chipset, bar: &Bar0, gsp_fw: &GspFirmware) -> Result<
>>              wpr2,
>>              heap,
>>              vf_partition_count: 0,
>> +            pmu_reserved_size: match chipset.arch() {
>> +                Architecture::BlackwellGB10x | Architecture::BlackwellGB20x => PMU_RESERVED_SIZE,
>> +                _ => 0,
>> +            },
> 
> I suspect you can just call `calc_pmu_reserved_size`, which seem to
> perform the exact same computation?

Yes. 

> 
>>          })
>>      }
>>  }
>> +
>> +/// Returns the PMU reserved memory size for `chipset`.
>> +#[expect(dead_code)]
>> +pub(crate) fn calc_pmu_reserved_size(chipset: Chipset) -> u32 {
>> +    match chipset.arch() {
>> +        Architecture::BlackwellGB10x | Architecture::BlackwellGB20x => PMU_RESERVED_SIZE,
>> +        _ => 0,
>> +    }
> 
> We should avoid these matches on Architecture in common code as much as
> possible - that's what the HALs are for. Which means that
> `calc_pmu_reserved_size` should call a HAL method to obtain the right
> size (I'd also rename it to just `pmu_reserved_size` as we are not
> computing anything at runtime).
> 

Yes.

>> +}
>> +
>> +/// PMU reserved size, aligned to 128KB.
>> +pub(crate) const PMU_RESERVED_SIZE: u32 = usize_into_u32::<
>> +    {
>> +        match const_align_up(SZ_8M + SZ_16M + SZ_4K, Alignment::new::<SZ_128K>()) {
>> +            Some(v) => v,
>> +            None => panic!("PMU_RESERVED_SIZE: alignment overflow"),
>> +        }
>> +    },
>> +>();
> 
> Consequently, this should be moved into the Blackwell HAL - which is
> where is belongs, as contrary to what its name implies in the current
> module, this reserved size does not apply to all architectures.

Right. This originated in bringup, when I didn't fully understand where
and when PMU reserved size came into play. Now it's clear, and yes it
needs a HAL.


thanks,
-- 
John Hubbard