Re: [PATCH 15/16] gpu: nova-core: mm: Add BAR1 user interface

[John Hubbard <jhubbard@nvidia.com>]

On 9/19/26 8:03 AM, Alexandre Courbot wrote:
> On Fri Sep 18, 2026 at 12:38 PM JST, Dave Airlie wrote:
>> On Wed, 9 Sept 2026 at 14:25, Eliot Courtney <ecourtney@nvidia.com> wrote:
>>>
>>> From: Joel Fernandes <joelagnelf@nvidia.com>
>>>
>>> Add the BAR1 user interface for CPU access to GPU virtual memory through
>>> the BAR1 aperture.
>>>
>>> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
>>> [ecourtney: map BAR1 in NovaCore, borrow it in Gpu and BarUser, no Devres]
>>> [ecourtney: update for the VramAddress raw API and gsp_resources chipset]
>>> [ecourtney: drop the owned GpuMm, pass it mutably through map and release]
>>> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
>>> ---
>>
>> BAR 1 and 2 need to be optionally detected and used. At least on SPARK
>> there is only BAR0.
>>
>> I've been playing with John's branch on spark and had to rework this
>> code to make BAR 1 optional.
> 
> Thanks Dave - indeed we also hit an issue on a device where the FB
> console was enabled (?), which preventing BAR1 from being used.
>

That's different: another device driver was using the GPU. People
should Kconfig their system to avoid having two device drivers
trying to claim the same hardware.

Once Nova get a bit further along, it will be a non-issue too,
because Nova can drive either an fbdev, or whatever the modern
alternative to that is.

  
> I know Eliot has a bunch of follow-ups in the pipe, Eliot can we make
> sure to dynamically detect and enable BAR1?

thanks,
-- 
John Hubbard