linux-kernel - Re: [PATCH] iommu: io-pgtable: Support non-coherent page tables

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Message-ID: <20190604234103.GH4814@minitux>
Date:   Tue, 4 Jun 2019 16:41:03 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>
Cc:     Vivek Gautam <vivek.gautam@...eaurora.org>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        Vivek Gautam <vgautam@....qualcomm.com>,
        open list <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] iommu: io-pgtable: Support non-coherent page tables

On Wed 15 May 23:47 PDT 2019, Vivek Gautam wrote:

> On Thu, May 16, 2019 at 5:03 AM Bjorn Andersson
> <bjorn.andersson@...aro.org> wrote:
> >
> > Describe the memory related to page table walks as non-cachable for iommu
> > instances that are not DMA coherent.
> >
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > ---
> >  drivers/iommu/io-pgtable-arm.c | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> > index 4e21efbc4459..68ff22ffd2cb 100644
> > --- a/drivers/iommu/io-pgtable-arm.c
> > +++ b/drivers/iommu/io-pgtable-arm.c
> > @@ -803,9 +803,15 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
> >                 return NULL;
> >
> >         /* TCR */
> > -       reg = (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
> > -             (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_IRGN0_SHIFT) |
> > -             (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_ORGN0_SHIFT);
> > +       if (cfg->quirks & IO_PGTABLE_QUIRK_NO_DMA) {
> > +               reg = (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
> > +                     (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_IRGN0_SHIFT) |
> > +                     (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_ORGN0_SHIFT);
> > +       } else {
> > +               reg = (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
> > +                     (ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_IRGN0_SHIFT) |
> > +                     (ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_ORGN0_SHIFT);
> > +       }
> 
> This looks okay to me based on the discussion that we had on a similar
> patch that I
> posted. So,
> Reviewed-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> 
> [1] https://lore.kernel.org/patchwork/patch/1032939/
> 

Will, Robin, any input on this patch?

Regards,
Bjorn