linux-kernel - Re: [PATCH v3 1/8] iommu: Add MMIO mapping type

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Date:	Thu, 11 Feb 2016 02:02:11 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Niklas Söderlund 
	<niklas.soderlund+renesas@...natech.se>
Cc:	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,
	robin.murphy@....com, 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

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.

>  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;

-- 
Regards,

Laurent Pinchart