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Message-ID: <56C3197C.8090903@arm.com>
Date: Tue, 16 Feb 2016 12:43:40 +0000
From: Robin Murphy <robin.murphy@....com>
To: Niklas Söderlund <niklas.soderlund@...natech.se>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
linux-renesas-soc@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
dmaengine@...r.kernel.org, iommu@...ts.linux-foundation.org,
vinod.koul@...el.com, geert+renesas@...der.be,
linus.walleij@...aro.org, dan.j.williams@...el.com, arnd@...db.de,
linux-arch@...r.kernel.org
Subject: Re: [PATCH v3 1/8] iommu: Add MMIO mapping type
On 16/02/16 12:06, Niklas Söderlund wrote:
> Hi Robin,
>
> Thanks for your update patch I will include it in my next version. But
> I'm sorry I do not understand, is your modification an addition or a
> substitution to your original patch?
Apologies for being confusing - that was a diff on top of the existing
patch, to be folded in. My original patch was only handling IOMMU_MMIO
for stage 2 PTEs, so we also need the extra code to handle the different
way of setting the appropriate memory type in stage 1 PTEs.
Robin.
> * Robin Murphy <robin.murphy@....com> [2016-02-11 15:57:26 +0000]:
>
>> On 11/02/16 00:02, Laurent Pinchart wrote:
>>> Hi Niklas,
>>>
>>> Thank you for the patch.
>>>
>>> On Wednesday 10 February 2016 01:57:51 Niklas Söderlund wrote:
>>>> From: Robin Murphy <robin.murphy@....com>
>>>>
>>>> On some platforms, MMIO regions might need slightly different treatment
>>>> compared to mapping regular memory; add the notion of MMIO mappings to
>>>> the IOMMU API's memory type flags, so that callers can let the IOMMU
>>>> drivers know to do the right thing.
>>>>
>>>> Signed-off-by: Robin Murphy <robin.murphy@....com>
>>>> Acked-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>>>
>>> Answering the question from the cover letter, yes, it's totally fine to pick
>>> the ack, that's actually expected.
>>>
>>>> ---
>>>> drivers/iommu/io-pgtable-arm.c | 4 +++-
>>>> include/linux/iommu.h | 1 +
>>>
>>> You might be asked to split this patch in two.
>>
>> Worse than that, you might also be asked to fix it up when the silly author
>> remembers that he did this on a stage-2-only ARM SMMU, and the attributes
>> for the stage 1 tables that the IPMMU uses are in a different code path:
>>
>> --->8---
>> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
>> index 5b5c299..7622c6e 100644
>> --- a/drivers/iommu/io-pgtable-arm.c
>> +++ b/drivers/iommu/io-pgtable-arm.c
>> @@ -354,7 +354,10 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct
>> arm_lpae_io_pgtable *data,
>> if (!(prot & IOMMU_WRITE) && (prot & IOMMU_READ))
>> pte |= ARM_LPAE_PTE_AP_RDONLY;
>>
>> - if (prot & IOMMU_CACHE)
>> + if (prot & IOMMU_MMIO)
>> + pte |= (ARM_LPAE_MAIR_ATTR_IDX_DEV
>> + << ARM_LPAE_PTE_ATTRINDX_SHIFT);
>> + else if (prot & IOMMU_CACHE)
>> pte |= (ARM_LPAE_MAIR_ATTR_IDX_CACHE
>> << ARM_LPAE_PTE_ATTRINDX_SHIFT);
>> } else {
>> --->8---
>>
>> Sorry for the bother,
>> Robin.
>>
>>>> 2 files changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
>>>> index 381ca5a..3ff4f87 100644
>>>> --- a/drivers/iommu/io-pgtable-arm.c
>>>> +++ b/drivers/iommu/io-pgtable-arm.c
>>>> @@ -364,7 +364,9 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct
>>>> arm_lpae_io_pgtable *data, pte |= ARM_LPAE_PTE_HAP_READ;
>>>> if (prot & IOMMU_WRITE)
>>>> pte |= ARM_LPAE_PTE_HAP_WRITE;
>>>> - if (prot & IOMMU_CACHE)
>>>> + if (prot & IOMMU_MMIO)
>>>> + pte |= ARM_LPAE_PTE_MEMATTR_DEV;
>>>> + else if (prot & IOMMU_CACHE)
>>>> pte |= ARM_LPAE_PTE_MEMATTR_OIWB;
>>>> else
>>>> pte |= ARM_LPAE_PTE_MEMATTR_NC;
>>>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>>>> index a5c539f..34b6432 100644
>>>> --- a/include/linux/iommu.h
>>>> +++ b/include/linux/iommu.h
>>>> @@ -30,6 +30,7 @@
>>>> #define IOMMU_WRITE (1 << 1)
>>>> #define IOMMU_CACHE (1 << 2) /* DMA cache coherency */
>>>> #define IOMMU_NOEXEC (1 << 3)
>>>> +#define IOMMU_MMIO (1 << 4) /* e.g. things like MSI doorbells */
>>>>
>>>> struct iommu_ops;
>>>> struct iommu_group;
>>>
>>
>
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