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Date: Tue, 18 Feb 2020 10:19:53 -0800
From: Rob Clark <robdclark@...il.com>
To: Jordan Crouse <jcrouse@...eaurora.org>
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, 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?
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.
BR,
-R
>
> 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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