linux-kernel - Re: [PATCH] iommu/ipmmu-vmsa: Drop LPAE Kconfig dependency

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Message-ID: <CANqRtoTuK4gcc7WMTcMQ4REtRL8oGtT_hLpo7UHgPiQ8e6L+9A@mail.gmail.com>
Date:	Tue, 20 Oct 2015 17:54:59 +0900
From:	Magnus Damm <magnus.damm@...il.com>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	iommu@...ts.linux-foundation.org,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	SH-Linux <linux-sh@...r.kernel.org>, joro <joro@...tes.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Simon Horman <horms+renesas@...ge.net.au>
Subject: Re: [PATCH] iommu/ipmmu-vmsa: Drop LPAE Kconfig dependency

Hi Laurent,

On Mon, Oct 19, 2015 at 3:42 PM, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
> Hi Magnus,
>
> Thank you for the patch.
>
> On Monday 19 October 2015 12:02:53 Magnus Damm wrote:
>> From: Magnus Damm <damm+renesas@...nsource.se>
>>
>> Neither the ARM page table code enabled by IOMMU_IO_PGTABLE_LPAE
>> nor the IPMMU_VMSA driver actually depends on ARM_LPAE, so get
>> rid of the dependency.
>>
>> Tested with ipmmu-vmsa on r8a7794 ALT and a kernel config using:
>>  # CONFIG_ARM_LPAE is not set
>
> The driver only supports the 40-bits page table format for now, hence the
> dependency on LPAE, but it indeed seems that the dependency is bogus. As long
> as the 8 MSBs of the translated address are all 0 I assume the output 40-bit
> address is usable on a 32-bit physical address system.
>
> How have you tested the patch ?

Modetest with local IPMMUMX enablement on r8a7794 ALT.

Cheers,

/ magnus
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