linux-kernel - Re: [RFC PATCH 3/4] drm/panfrost: Support ARM_64_LPAE

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Message-ID: <20250227093237.33aaf496@collabora.com>
Date: Thu, 27 Feb 2025 09:32:37 +0100
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Ariel D'Alessandro <ariel.dalessandro@...labora.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 robh@...nel.org, steven.price@....com, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch
Subject: Re: [RFC PATCH 3/4] drm/panfrost: Support ARM_64_LPAE_S1 page table

On Thu, 27 Feb 2025 09:30:30 +0100
Boris Brezillon <boris.brezillon@...labora.com> wrote:

> > Bifrost MMUs support AArch64 4kB granule specification. However,
> > panfrost only enables MMU in legacy mode, despite the presence of the
> > HW_FEATURE_AARCH64_MMU feature flag.
> > 
> > This commit adds support to use page tables according to AArch64 4kB
> > granule specification. This feature is enabled conditionally based on
> > the GPU model's HW_FEATURE_AARCH64_MMU feature flag.
> > 
> > Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@...labora.com>
> > ---
> >  drivers/gpu/drm/panfrost/panfrost_device.h |   1 +
> >  drivers/gpu/drm/panfrost/panfrost_mmu.c    | 118 +++++++++++++++++----
> >  drivers/gpu/drm/panfrost/panfrost_regs.h   |  29 +++++
> >  3 files changed, 128 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> > index cffcb0ac7c11..dea252f43c58 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> > +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> > @@ -153,6 +153,7 @@ struct panfrost_device {
> >  };
> >  
> >  struct panfrost_mmu {
> > +	void (*enable)(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);  
> 
> The enable sequence is the same, it's just the transtab, memattr and
> transcfg values that differ depending on the format, so let's prepare
> them at panfrost_mmu init time, and cache them here.

Just to be clear, I meant replace this ->enable() function pointer by a

	struct {
		u64 transtab;
		u64 memattr;
		u64 transcfg;
	} cfg;

field.

> 
> >  	struct panfrost_device *pfdev;
> >  	struct kref refcount;
> >  	struct io_pgtable_cfg pgtbl_cfg;