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Date: Thu, 23 May 2019 18:04:27 +0530
From: Vivek Gautam <vivek.gautam@...eaurora.org>
To: Robin Murphy <robin.murphy@....com>
Cc: Will Deacon <will.deacon@....com>,
"list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
Roedel <joro@...tes.org>," <joro@...tes.org>,
"list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
pratikp@...eaurora.org, open list <linux-kernel@...r.kernel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
pdaly@...eaurora.org
Subject: Re: [PATCH v5 1/1] iommu/io-pgtable-arm: Add support to use system cache
On Thu, May 23, 2019 at 4:11 PM Robin Murphy <robin.murphy@....com> wrote:
>
> On 2019-05-16 10:30 am, Vivek Gautam wrote:
> > Few Qualcomm platforms such as, sdm845 have an additional outer
> > cache called as System cache, aka. Last level cache (LLC) that
> > allows non-coherent devices to upgrade to using caching.
> > This cache sits right before the DDR, and is tightly coupled
> > with the memory controller. The clients using this cache request
> > their slices from this system cache, make it active, and can then
> > start using it.
> >
> > There is a fundamental assumption that non-coherent devices can't
> > access caches. This change adds an exception where they *can* use
> > some level of cache despite still being non-coherent overall.
> > The coherent devices that use cacheable memory, and CPU make use of
> > this system cache by default.
> >
> > Looking at memory types, we have following -
> > a) Normal uncached :- MAIR 0x44, inner non-cacheable,
> > outer non-cacheable;
> > b) Normal cached :- MAIR 0xff, inner read write-back non-transient,
> > outer read write-back non-transient;
> > attribute setting for coherenet I/O devices.
> > and, for non-coherent i/o devices that can allocate in system cache
> > another type gets added -
> > c) Normal sys-cached :- MAIR 0xf4, inner non-cacheable,
> > outer read write-back non-transient
> >
> > Coherent I/O devices use system cache by marking the memory as
> > normal cached.
> > Non-coherent I/O devices should mark the memory as normal
> > sys-cached in page tables to use system cache.
> >
> > Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
>
> Acked-by: Robin Murphy <robin.murphy@....com>
Thanks a lot Robin.
regards
Vivek
>
> There's a remote possibility that the IOMMU prot flag might be able to
> be somewhat generalised in future for panfrost, as Mali appears to have
> some pretty funky notions of cacheability, but this certainly looks fine
> for now, thanks.
>
> Robin.
>
> > ---
> >
> > V3 version of this patch and related series can be found at [1].
> > V4 of this patch is available at [2].
> >
> > The example usage of how a smmu master can make use of this protection
> > flag and set the correct memory attributes to start using system cache,
> > can be found at [3]; and here at [3] IOMMU_UPSTREAM_HINT is same as
> > IOMMU_QCOM_SYS_CACHE.
> >
> > Changes since v4:
> > - Changed ARM_LPAE_MAIR_ATTR_QCOM_SYS_CACHE to
> > ARM_LPAE_MAIR_ATTR_INC_OWBRWA.
> > - Changed ARM_LPAE_MAIR_ATTR_IDX_QCOM_SYS_CACHE to
> > ARM_LPAE_MAIR_ATTR_IDX_INC_OCACHE.
> > - Added comments to iommu protection flag - IOMMU_QCOM_SYS_CACHE.
> >
> > Changes since v3:
> > - Dropping support to cache i/o page tables to system cache. Getting support
> > for data buffers is the first step.
> > Removed io-pgtable quirk and related change to add domain attribute.
> >
> > Glmark2 numbers on SDM845 based cheza board:
> >
> > S.No.| with LLC support | without LLC support
> > | for data buffers |
> > ---------------------------------------------------
> > 1 | 4480; 72.3fps | 4042; 65.2fps
> > 2 | 4500; 72.6fps | 4039; 65.1fps
> > 3 | 4523; 72.9fps | 4106; 66.2fps
> > 4 | 4489; 72.4fps | 4104; 66.2fps
> > 5 | 4518; 72.9fps | 4072; 65.7fps
> >
> > [1] https://patchwork.kernel.org/cover/10772629/
> > [2] https://lore.kernel.org/patchwork/patch/1072936/
> > [3] https://patchwork.kernel.org/patch/10302791/
> >
> > drivers/iommu/io-pgtable-arm.c | 9 ++++++++-
> > include/linux/iommu.h | 6 ++++++
> > 2 files changed, 14 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> > index 4e21efbc4459..2454ac11aa97 100644
> > --- a/drivers/iommu/io-pgtable-arm.c
> > +++ b/drivers/iommu/io-pgtable-arm.c
> > @@ -167,10 +167,12 @@
> > #define ARM_LPAE_MAIR_ATTR_MASK 0xff
> > #define ARM_LPAE_MAIR_ATTR_DEVICE 0x04
> > #define ARM_LPAE_MAIR_ATTR_NC 0x44
> > +#define ARM_LPAE_MAIR_ATTR_INC_OWBRWA 0xf4
> > #define ARM_LPAE_MAIR_ATTR_WBRWA 0xff
> > #define ARM_LPAE_MAIR_ATTR_IDX_NC 0
> > #define ARM_LPAE_MAIR_ATTR_IDX_CACHE 1
> > #define ARM_LPAE_MAIR_ATTR_IDX_DEV 2
> > +#define ARM_LPAE_MAIR_ATTR_IDX_INC_OCACHE 3
> >
> > #define ARM_MALI_LPAE_TTBR_ADRMODE_TABLE (3u << 0)
> > #define ARM_MALI_LPAE_TTBR_READ_INNER BIT(2)
> > @@ -470,6 +472,9 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
> > else if (prot & IOMMU_CACHE)
> > pte |= (ARM_LPAE_MAIR_ATTR_IDX_CACHE
> > << ARM_LPAE_PTE_ATTRINDX_SHIFT);
> > + else if (prot & IOMMU_QCOM_SYS_CACHE)
> > + pte |= (ARM_LPAE_MAIR_ATTR_IDX_INC_OCACHE
> > + << ARM_LPAE_PTE_ATTRINDX_SHIFT);
> > }
> >
> > if (prot & IOMMU_NOEXEC)
> > @@ -857,7 +862,9 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
> > (ARM_LPAE_MAIR_ATTR_WBRWA
> > << ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_CACHE)) |
> > (ARM_LPAE_MAIR_ATTR_DEVICE
> > - << ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_DEV));
> > + << ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_DEV)) |
> > + (ARM_LPAE_MAIR_ATTR_INC_OWBRWA
> > + << ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_INC_OCACHE));
> >
> > cfg->arm_lpae_s1_cfg.mair[0] = reg;
> > cfg->arm_lpae_s1_cfg.mair[1] = 0;
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index a815cf6f6f47..8ee3fbaf5855 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -41,6 +41,12 @@
> > * if the IOMMU page table format is equivalent.
> > */
> > #define IOMMU_PRIV (1 << 5)
> > +/*
> > + * Non-coherent masters on few Qualcomm SoCs can use this page protection flag
> > + * to set correct cacheability attributes to use an outer level of cache -
> > + * last level cache, aka system cache.
> > + */
> > +#define IOMMU_QCOM_SYS_CACHE (1 << 6)
> >
> > struct iommu_ops;
> > struct iommu_group;
> >
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
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