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

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Message-ID: <20160216133055.GB26710@bigcity.dyn.berto.se>
Date:	Tue, 16 Feb 2016 14:30:55 +0100
From:	Niklas Söderlund 
	<niklas.soderlund@...natech.se>
To:	Robin Murphy <robin.murphy@....com>
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

* Robin Murphy <robin.murphy@....com> [2016-02-16 12:43:40 +0000]:

> 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.

That's what I though but wanted to be clear, thanks for clarifying. I
will fold the diff into your patch and keep your SoB line and send it
out with my series, hope that's a OK way for me to handle it.

Once more thanks for your patch and feedback.

>
> 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;
> >>>
> >>
> >
>