linux-kernel - Re: [PATCH v3 1/3] iommu: io-pgtable: Add ARM Mali midgard MMU page table format

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Date:   Mon, 1 Apr 2019 20:11:00 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Rob Herring <robh@...nel.org>, dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Lyude Paul <lyude@...hat.com>, Eric Anholt <eric@...olt.net>,
        Neil Armstrong <narmstrong@...libre.com>
Subject: Re: [PATCH v3 1/3] iommu: io-pgtable: Add ARM Mali midgard MMU page
 table format

On 01/04/2019 08:47, Rob Herring wrote:
> ARM Mali midgard GPU is similar to standard 64-bit stage 1 page tables, but
> have a few differences. Add a new format type to represent the format. The
> input address size is 48-bits and the output address size is 40-bits (and
> possibly less?). Note that the later bifrost GPUs follow the standard
> 64-bit stage 1 format.
> 
> The differences in the format compared to 64-bit stage 1 format are:
> 
> The 3rd level page entry bits are 0x1 instead of 0x3 for page entries.
> 
> The access flags are not read-only and unprivileged, but read and write.
> This is similar to stage 2 entries, but the memory attributes field matches
> stage 1 being an index.
> 
> The nG bit is not set by the vendor driver. This one didn't seem to matter,
> but we'll keep it aligned to the vendor driver.
> 
> Cc: Will Deacon <will.deacon@....com>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: iommu@...ts.linux-foundation.org
> Signed-off-by: Rob Herring <robh@...nel.org>
> ---
> Please ack this as I need to apply it to the drm-misc tree. Or we need a
> stable branch with this patch.

With the diff below squashed in to address my outstanding style nits,

Acked-by: Robin Murphy <robin.murphy@....com>

I don't foresee any conflicting io-pgtable changes to prevent this going 
via DRM, but I'll leave the final say up to Joerg.

Thanks,
Robin.

----->8-----
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 98551d0cff59..55ed039da166 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -197,12 +197,13 @@ struct arm_lpae_io_pgtable {

  typedef u64 arm_lpae_iopte;

-static inline bool iopte_leaf(arm_lpae_iopte pte, int l, enum 
io_pgtable_fmt fmt)
+static inline bool iopte_leaf(arm_lpae_iopte pte, int lvl,
+			      enum io_pgtable_fmt fmt)
  {
-	if ((l == (ARM_LPAE_MAX_LEVELS - 1)) && (fmt != ARM_MALI_LPAE))
-		return iopte_type(pte,l) == ARM_LPAE_PTE_TYPE_PAGE;
+	if (lvl == (ARM_LPAE_MAX_LEVELS - 1) && fmt != ARM_MALI_LPAE)
+		return iopte_type(pte, lvl) == ARM_LPAE_PTE_TYPE_PAGE;

-	return iopte_type(pte,l) == ARM_LPAE_PTE_TYPE_BLOCK;
+	return iopte_type(pte, lvl) == ARM_LPAE_PTE_TYPE_BLOCK;
  }

  static arm_lpae_iopte paddr_to_iopte(phys_addr_t paddr,
@@ -310,13 +311,10 @@ static void __arm_lpae_init_pte(struct 
arm_lpae_io_pgtable *data,
  	if (data->iop.cfg.quirks & IO_PGTABLE_QUIRK_ARM_NS)
  		pte |= ARM_LPAE_PTE_NS;

-	if (lvl == ARM_LPAE_MAX_LEVELS - 1) {
-		if (data->iop.fmt == ARM_MALI_LPAE)
-			pte |= ARM_LPAE_PTE_TYPE_BLOCK;
-		else
-			pte |= ARM_LPAE_PTE_TYPE_PAGE;
-	} else
+	if (data->iop.fmt != ARM_MALI_LPAE && lvl != ARM_LPAE_MAX_LEVELS - 1)
  		pte |= ARM_LPAE_PTE_TYPE_BLOCK;
+	else
+		pte |= ARM_LPAE_PTE_TYPE_PAGE;

  	if (data->iop.fmt != ARM_MALI_LPAE)
  		pte |= ARM_LPAE_PTE_AF;