Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

[Geert Uytterhoeven]

Hi Christoph,

CC soc

On Mon, Oct 9, 2023 at 11:43 AM Christoph Hellwig <hch@lst.de> wrote:
> On Mon, Oct 09, 2023 at 11:34:55AM +0200, Geert Uytterhoeven wrote:
> > The fix you are referring too is probably commit c1ec4b450ab729e3
> > ("soc: renesas: Make ARCH_R9A07G043 (riscv version) depend
> > on NONPORTABLE") in next-20231006 and later.  It is not yet upstream.
> >
> > Still, it merely makes ARCH_R9A07G043 (which selects DMA_GLOBAL_POOL)
> > depend on ARCH_R9A07G043.
> > RISCV_DMA_NONCOHERENT still selects DMA_DIRECT_REMAP, so both can end
> > up being enabled.
>
> Ok, so we need to actually fix this properly.  Lad, can you respin
> the fix to not select DMA_DIRECT_REMAP, for ARCH_R9A07G043?

ARCH_R9A07G043 does not select DMA_DIRECT_REMAP directly,
RISCV_DMA_NONCOHERENT does.  And there are other users of
RISCV_DMA_NONCOHERENT (RISCV_ISA_ZICBOM and ERRATA_THEAD_CMO).
Should the selection of DMA_DIRECT_REMAP moved to their users?

Note that the fix is already in soc/for-next, so we need coordination
with the soc people.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

[Robin Murphy]

On 2023-10-09 10:51, Geert Uytterhoeven wrote:
> Hi Christoph,
> 
> CC soc
> 
> On Mon, Oct 9, 2023 at 11:43 AM Christoph Hellwig <hch@lst.de> wrote:
>> On Mon, Oct 09, 2023 at 11:34:55AM +0200, Geert Uytterhoeven wrote:
>>> The fix you are referring too is probably commit c1ec4b450ab729e3
>>> ("soc: renesas: Make ARCH_R9A07G043 (riscv version) depend
>>> on NONPORTABLE") in next-20231006 and later.  It is not yet upstream.
>>>
>>> Still, it merely makes ARCH_R9A07G043 (which selects DMA_GLOBAL_POOL)
>>> depend on ARCH_R9A07G043.
>>> RISCV_DMA_NONCOHERENT still selects DMA_DIRECT_REMAP, so both can end
>>> up being enabled.
>>
>> Ok, so we need to actually fix this properly.  Lad, can you respin
>> the fix to not select DMA_DIRECT_REMAP, for ARCH_R9A07G043?
> 
> ARCH_R9A07G043 does not select DMA_DIRECT_REMAP directly,
> RISCV_DMA_NONCOHERENT does.  And there are other users of
> RISCV_DMA_NONCOHERENT (RISCV_ISA_ZICBOM and ERRATA_THEAD_CMO).
> Should the selection of DMA_DIRECT_REMAP moved to their users?

No, the selection of DMA_GLOBAL_POOL should be removed from 
RISV_DMA_NONCOHERENT and selected directly by ARCH_R9A07G043 (along with 
any of the other implied symbols it needs). Or if as suggested this 
physical-attribute-remap wackiness is due to show up on more platforms 
as well, maybe have a common config for that which selects 
DMA_GLOBAL_POOL plus the relevant cache maintenance extensions as an 
equivalent to RISCV_DMA_NONCOHERENT, and can itself explicitly depend on 
NONPORTABLE for clarity.

Thanks,
Robin.

> Note that the fix is already in soc/for-next, so we need coordination
> with the soc people.
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
> 

Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

[Geert Uytterhoeven]

Hi Robin,

On Mon, Oct 9, 2023 at 12:04 PM Robin Murphy <robin.murphy@arm.com> wrote:
> On 2023-10-09 10:51, Geert Uytterhoeven wrote:
> > On Mon, Oct 9, 2023 at 11:43 AM Christoph Hellwig <hch@lst.de> wrote:
> >> On Mon, Oct 09, 2023 at 11:34:55AM +0200, Geert Uytterhoeven wrote:
> >>> The fix you are referring too is probably commit c1ec4b450ab729e3
> >>> ("soc: renesas: Make ARCH_R9A07G043 (riscv version) depend
> >>> on NONPORTABLE") in next-20231006 and later.  It is not yet upstream.
> >>>
> >>> Still, it merely makes ARCH_R9A07G043 (which selects DMA_GLOBAL_POOL)
> >>> depend on ARCH_R9A07G043.
> >>> RISCV_DMA_NONCOHERENT still selects DMA_DIRECT_REMAP, so both can end
> >>> up being enabled.
> >>
> >> Ok, so we need to actually fix this properly.  Lad, can you respin
> >> the fix to not select DMA_DIRECT_REMAP, for ARCH_R9A07G043?
> >
> > ARCH_R9A07G043 does not select DMA_DIRECT_REMAP directly,
> > RISCV_DMA_NONCOHERENT does.  And there are other users of
> > RISCV_DMA_NONCOHERENT (RISCV_ISA_ZICBOM and ERRATA_THEAD_CMO).
> > Should the selection of DMA_DIRECT_REMAP moved to their users?
>
> No, the selection of DMA_GLOBAL_POOL should be removed from
> RISV_DMA_NONCOHERENT and selected directly by ARCH_R9A07G043 (along with
> any of the other implied symbols it needs). Or if as suggested this
> physical-attribute-remap wackiness is due to show up on more platforms
> as well, maybe have a common config for that which selects
> DMA_GLOBAL_POOL plus the relevant cache maintenance extensions as an
> equivalent to RISCV_DMA_NONCOHERENT, and can itself explicitly depend on
> NONPORTABLE for clarity.

RISCV_DMA_NONCOHERENT does not select DMA_GLOBAL_POOL,
ARCH_R9A07G043 selects DMA_GLOBAL_POOL.
RISCV_DMA_NONCOHERENT does select DMA_DIRECT_REMAP if MMU.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

[Christoph Hellwig]

On Mon, Oct 09, 2023 at 01:10:26PM +0200, Geert Uytterhoeven wrote:
> RISCV_DMA_NONCOHERENT does not select DMA_GLOBAL_POOL,
> ARCH_R9A07G043 selects DMA_GLOBAL_POOL.
> RISCV_DMA_NONCOHERENT does select DMA_DIRECT_REMAP if MMU.

Yeah, and we'll basically need to split RISCV_DMA_NONCOHERENT into
an option for each type of non-coherent support.  This is why we
should never have added support for any of the non-standard versions,
as it's turning into a giant mess.

Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

[Robin Murphy]

On 09/10/2023 1:48 pm, Christoph Hellwig wrote:
> On Mon, Oct 09, 2023 at 01:10:26PM +0200, Geert Uytterhoeven wrote:
>> RISCV_DMA_NONCOHERENT does not select DMA_GLOBAL_POOL,
>> ARCH_R9A07G043 selects DMA_GLOBAL_POOL.
>> RISCV_DMA_NONCOHERENT does select DMA_DIRECT_REMAP if MMU.

Bleh, guess I should have known better than to trust my Monday morning 
memory without double-checking the code :)

> Yeah, and we'll basically need to split RISCV_DMA_NONCOHERENT into
> an option for each type of non-coherent support.  This is why we
> should never have added support for any of the non-standard versions,
> as it's turning into a giant mess.

Indeed the main point I was trying to get at is for ARCH_R9A07G043 (or 
rather possibly ERRATA_ANDES_CMO) to not select RISCV_DMA_NONCOHERENT in 
its current form, since that ending up selecting DMA_DIRECT_REMAP on a 
platform which can't support it is the thing that's most obviously wrong.

Thanks,
Robin.