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Date: Tue, 18 Feb 2020 11:41:05 -0700
From: Jordan Crouse <jcrouse@...eaurora.org>
To: Rob Clark <robdclark@...il.com>
Cc: "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
Robin Murphy <robin.murphy@....com>,
Will Deacon <will@...nel.org>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@...ts.infradead.org>,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Joerg Roedel <joro@...tes.org>
Subject: Re: [RFC PATCH v1] iommu/arm-smmu: Allow domains to choose a context
bank
On Tue, Feb 18, 2020 at 10:19:53AM -0800, Rob Clark wrote:
> On Tue, Jan 28, 2020 at 2:34 PM Jordan Crouse <jcrouse@...eaurora.org> wrote:
> >
> > Domains which are being set up for split pagetables usually want to be
> > on a specific context bank for hardware reasons. Force the context
> > bank for domains with the split-pagetable quirk to context bank 0.
> > If context bank 0 is taken, move that context bank to another unused
> > bank and rewrite the stream matching registers accordingly.
>
> Is the only reason for dealing with the case that bank 0 is already in
> use, due to the DMA domain that gets setup before driver probes?
Right. On Adreno GPUs only one context bank at a time is accessible from the
GPU through an aperture which defaults to context bank 0 and as you might
expect, the aperture controls are protected by the secure world on AC enabled
targets.
Some of the newer targets have a SCM call to switch the aperture but for all the
currently merged platforms we are forced to use context bank 0.
> I'm kinda thinking that we need to invent a way to unwind/detatch the
> DMA domain, and unhook the iommu-dmaops, since this seems to already
> be already causing problems with dma-bufs imported from other drivers
> (who expect that dma_map_*(), with the importing device's dev ptr,
> will do something sane.
That could work, assuming that we could guarantee that our new replacement
domain got the context bank we wanted.
Jordan
> >
> > This is be used by [1] and [2] to leave context bank 0 open so that
> > the Adreno GPU can program it.
> >
> > [1] https://lists.linuxfoundation.org/pipermail/iommu/2020-January/041438.html
> > [2] https://lists.linuxfoundation.org/pipermail/iommu/2020-January/041444.html
> >
> > Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
> > ---
> >
> > drivers/iommu/arm-smmu.c | 63 +++++++++++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 59 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> > index 85a6773..799a254 100644
> > --- a/drivers/iommu/arm-smmu.c
> > +++ b/drivers/iommu/arm-smmu.c
> > @@ -254,6 +254,43 @@ static int __arm_smmu_alloc_bitmap(unsigned long *map, int start, int end)
> > return idx;
> > }
> >
> > +static void arm_smmu_write_s2cr(struct arm_smmu_device *smmu, int idx);
> > +
> > +static int __arm_smmu_alloc_cb(struct arm_smmu_device *smmu, int start,
> > + int target)
> > +{
> > + int new, i;
> > +
> > + /* Allocate a new context bank id */
> > + new = __arm_smmu_alloc_bitmap(smmu->context_map, start,
> > + smmu->num_context_banks);
> > +
> > + if (new < 0)
> > + return new;
> > +
> > + /* If no target is set or we actually got the bank index we wanted */
> > + if (target == -1 || new == target)
> > + return new;
> > +
> > + /* Copy the context configuration to the new index */
> > + memcpy(&smmu->cbs[new], &smmu->cbs[target], sizeof(*smmu->cbs));
> > + smmu->cbs[new].cfg->cbndx = new;
> > +
> > + /* FIXME: Do we need locking here? */
> > + for (i = 0; i < smmu->num_mapping_groups; i++) {
> > + if (smmu->s2crs[i].cbndx == target) {
> > + smmu->s2crs[i].cbndx = new;
> > + arm_smmu_write_s2cr(smmu, i);
> > + }
> > + }
> > +
> > + /*
> > + * FIXME: Does getting here imply that 'target' is already set in the
> > + * context_map?
> > + */
> > + return target;
> > +}
> > +
> > static void __arm_smmu_free_bitmap(unsigned long *map, int idx)
> > {
> > clear_bit(idx, map);
> > @@ -770,6 +807,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> > struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> > struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> > unsigned long quirks = 0;
> > + int forcecb = -1;
> >
> > mutex_lock(&smmu_domain->init_mutex);
> > if (smmu_domain->smmu)
> > @@ -844,8 +882,25 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> > * SEP_UPSTREAM so we don't need to reduce the size of
> > * the ias to account for the sign extension bit
> > */
> > - if (smmu_domain->split_pagetables)
> > - quirks |= IO_PGTABLE_QUIRK_ARM_TTBR1;
> > + if (smmu_domain->split_pagetables) {
> > + /*
> > + * If split pagetables are enabled, assume that
> > + * the user's intent is to use per-instance
> > + * pagetables which, at least on a QCOM target,
> > + * means that this domain should be on context
> > + * bank 0.
> > + */
> > +
> > + /*
> > + * If we can't force to context bank 0 then
> > + * don't bother enabling split pagetables which
> > + * then would not allow aux domains
> > + */
> > + if (start == 0) {
> > + forcecb = 0;
> > + quirks |= IO_PGTABLE_QUIRK_ARM_TTBR1;
> > + }
> > + }
> > } else if (cfg->fmt == ARM_SMMU_CTX_FMT_AARCH32_L) {
> > fmt = ARM_32_LPAE_S1;
> > ias = min(ias, 32UL);
> > @@ -883,8 +938,8 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> > ret = -EINVAL;
> > goto out_unlock;
> > }
> > - ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,
> > - smmu->num_context_banks);
> > +
> > + ret = __arm_smmu_alloc_cb(smmu, start, forcecb);
> > if (ret < 0)
> > goto out_unlock;
> >
> > --
> > 2.7.4
--
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