Re: [RFC PATCH 2/4] drm/panfrost: Split LPAE MMU TRANSTAB register values

[Ariel D'Alessandro]

Boris,

On 2/27/25 5:25 AM, Boris Brezillon wrote:
> On Wed, 26 Feb 2025 15:30:41 -0300
> Ariel D'Alessandro <ariel.dalessandro@xxxxxxxxxxxxx> wrote:

[snip]

> > diff --git a/drivers/gpu/drm/panfrost/panfrost_regs.h b/drivers/gpu/drm/panfrost/panfrost_regs.h
> > index b5f279a19a08..4e6064d5feaa 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_regs.h
> > +++ b/drivers/gpu/drm/panfrost/panfrost_regs.h
> > @@ -317,14 +317,19 @@
> >   #define MMU_AS_STRIDE			(1 << MMU_AS_SHIFT)
> >   
> >   /*
> > - * Begin LPAE MMU TRANSTAB register values
> > + * Begin LPAE MMU TRANSTAB register values (legacy mode)
> >    */
> > -#define AS_TRANSTAB_LPAE_ADDR_SPACE_MASK	0xfffffffffffff000
> > -#define AS_TRANSTAB_LPAE_ADRMODE_IDENTITY	0x2
> > -#define AS_TRANSTAB_LPAE_ADRMODE_TABLE		0x3
> > -#define AS_TRANSTAB_LPAE_ADRMODE_MASK		0x3
> > -#define AS_TRANSTAB_LPAE_READ_INNER		BIT(2)
> > -#define AS_TRANSTAB_LPAE_SHARE_OUTER		BIT(4)
> > +#define AS_TRANSTAB_LEGACY_ADDR_SPACE_MASK	0xfffffffffffff000
> > +#define AS_TRANSTAB_LEGACY_ADRMODE_IDENTITY	0x2
> > +#define AS_TRANSTAB_LEGACY_ADRMODE_TABLE	0x3
> > +#define AS_TRANSTAB_LEGACY_ADRMODE_MASK		0x3
> > +#define AS_TRANSTAB_LEGACY_READ_INNER		BIT(2)
> > +#define AS_TRANSTAB_LEGACY_SHARE_OUTER		BIT(4)
>
> How about we keep AS_TRANSTAB_LPAE_ here and prefix the new reg values
> with AS_xxx_AARCH64_ when there's a collision between the two formats.

Agreed. Will use AS_TRANSTAB_AARCH64_4K_ prefix for the new ones.

> > +
> > +/*
> > + * Begin LPAE MMU TRANSTAB register values (no-legacy mode)
> > + */
> > +#define AS_TRANSTAB_LPAE_ADDR_SPACE_MASK	0xfffffffffffffff0
>
> It looks like we're not use AS_TRANSTAB_LPAE_ADDR_SPACE_MASK, so I'm
> not sure it's worth defining the mask for the AARCH64 format.

None of the original AS_TRANSTAB_LPAE_* values are used, but these refer 
to the LPAE (legacy mode) format.

The new mask for the AARCH64 format is required by the follow up patch 
`[RFC PATCH 3/4] drm/panfrost: Support ARM_64_LPAE_S1 page table`. It 
probably makes sense to just squash it now that this patch got 
simplified and the naming will be more clear.

I'll send a new patchset version with these changes.

Thanks!

--
Ariel D'Alessandro
Software Engineer

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