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Date:   Thu, 30 Mar 2023 07:25:23 +0100
From:   Conor Dooley <conor.dooley@microchip.com>
To:     Randy Dunlap <rdunlap@infradead.org>
CC:     <linux-kernel@vger.kernel.org>, Joerg Roedel <joro@8bytes.org>,
        Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>, <iommu@lists.linux.dev>,
        Conor Dooley <conor@kernel.org>,
        <linux-riscv@lists.infradead.org>, <geert+renesas@glider.be>
Subject: Re: [PATCH] iommu: PGTABLE_LPAE is also for RISCV
Message-ID: <e1b6f12a-899b-4985-8725-556bcb5d0991@spud>
References: <20230330060105.29460-1-rdunlap@infradead.org>
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Hey Randy,

On Wed, Mar 29, 2023 at 11:01:05PM -0700, Randy Dunlap wrote:
> On riscv64, linux-next-20233030 (and for several days earlier),
> there is a kconfig warning:
>=20
> WARNING: unmet direct dependencies detected for IOMMU_IO_PGTABLE_LPAE
>   Depends on [n]: IOMMU_SUPPORT [=3Dy] && (ARM || ARM64 || COMPILE_TEST [=
=3Dn]) && !GENERIC_ATOMIC64 [=3Dn]
>   Selected by [y]:
>   - IPMMU_VMSA [=3Dy] && IOMMU_SUPPORT [=3Dy] && (ARCH_RENESAS [=3Dy] || =
COMPILE_TEST [=3Dn]) && !GENERIC_ATOMIC64 [=3Dn]
>=20
> and build errors:
>=20
> riscv64-linux-ld: drivers/iommu/io-pgtable-arm.o: in function `.L140':
> io-pgtable-arm.c:(.init.text+0x1e8): undefined reference to `alloc_io_pgt=
able_ops'
> riscv64-linux-ld: drivers/iommu/io-pgtable-arm.o: in function `.L168':
> io-pgtable-arm.c:(.init.text+0xab0): undefined reference to `free_io_pgta=
ble_ops'
> riscv64-linux-ld: drivers/iommu/ipmmu-vmsa.o: in function `.L140':
> ipmmu-vmsa.c:(.text+0xbc4): undefined reference to `free_io_pgtable_ops'
> riscv64-linux-ld: drivers/iommu/ipmmu-vmsa.o: in function `.L0 ':
> ipmmu-vmsa.c:(.text+0x145e): undefined reference to `alloc_io_pgtable_ops'
>=20
> Add RISCV as an allowed ARCH dependency to fix these problems.
>=20
> Fixes: d286a58bc8f4 ("iommu: Tidy up io-pgtable dependencies")
> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Will Deacon <will@kernel.org>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: iommu@lists.linux.dev
> Cc: Conor Dooley <conor@kernel.org>
> Cc: linux-riscv@lists.infradead.org
> ---
>  drivers/iommu/Kconfig |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff -- a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -32,7 +32,7 @@ config IOMMU_IO_PGTABLE
>  config IOMMU_IO_PGTABLE_LPAE
>  	bool "ARMv7/v8 Long Descriptor Format"

I'm probably missing something here, but why would we want to enable
"ARMv7/v8 Long Descriptor Format" on RISC-V?
Would it not be better to make the Renesas depend on, rather than
select the option? It does seem highly arch specific, and I feel like
Geert previously mentioned that the RZ/Five (their RISC-V offering)
didn't use it.

Cheers,
Conor.

>  	select IOMMU_IO_PGTABLE
> -	depends on ARM || ARM64 || COMPILE_TEST
> +	depends on ARM || ARM64 || RISCV || COMPILE_TEST
>  	depends on !GENERIC_ATOMIC64	# for cmpxchg64()
>  	help
>  	  Enable support for the ARM long descriptor pagetable format.
>=20

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