Re: [PATCH 4/8] drm/panthor: Add support for protected memory allocation in panthor

[Maxime Ripard <mripard@kernel.org>]

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Hi,

On Tue, May 05, 2026 at 04:05:10PM +0200, Ketil Johnsen wrote:
> From: Florent Tomasin <florent.tomasin@arm.com>
> 
> This patch allows Panthor to allocate buffer objects from a
> protected heap. The Panthor driver should be seen as a consumer
> of the heap and not an exporter.
> 
> Protected memory buffers needed by the Panthor driver:
> - On CSF FW load, the Panthor driver must allocate a protected
>   buffer object to hold data to use by the FW when in protected
>   mode. This protected buffer object is owned by the device
>   and does not belong to a process.
> - On CSG creation, the Panthor driver must allocate a protected
>   suspend buffer object for the FW to store data when suspending
>   the CSG while in protected mode. The kernel owns this allocation
>   and does not allow user space mapping. The format of the data
>   in this buffer is only known by the FW and does not need to be
>   shared with other entities.
> 
> The driver will retrieve the protected heap using the name of the
> heap provided to the driver as module parameter.

I know it's what dma_heap_find asks for, but I wonder if it wouldn't be
better in the device tree and lookup through the device node? heaps are
going to have a node anyway, right?

This would allow you to have a default that works and not mess to much
with the kernel parameters that aren't always easy to change for
end-users.

Maxime

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