lkml.org 
[lkml]   [2020]   [Sep]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v3 8/8] iommu/arm-smmu-qcom: Setup identity domain for boot mappings
From
Date
On 2020-09-04 16:55, Bjorn Andersson wrote:
> With many Qualcomm platforms not having functional S2CR BYPASS a
> temporary IOMMU domain, without translation, needs to be allocated in
> order to allow these memory transactions.
>
> Unfortunately the boot loader uses the first few context banks, so
> rather than overwriting a active bank the last context bank is used and
> streams are diverted here during initialization.
>
> This also performs the readback of SMR registers for the Qualcomm
> platform, to trigger the mechanism.
>
> This is based on prior work by Thierry Reding and Laurentiu Tudor.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
>
> Changes since v2:
> - Combined from pieces spread between the Qualcomm impl and generic code in v2.
> - Moved to use the newly introduced inherit_mapping op.
>
> drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 33 ++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 70a1eaa52e14..a54302190932 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -12,6 +12,7 @@
> struct qcom_smmu {
> struct arm_smmu_device smmu;
> bool bypass_broken;
> + struct iommu_domain *identity;
> };
>
> static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
> @@ -228,6 +229,37 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
> return 0;
> }
>
> +static int qcom_smmu_inherit_mappings(struct arm_smmu_device *smmu)
> +{
> + struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
> + int cbndx;
> + u32 smr;
> + int i;
> +
> + qsmmu->identity = arm_smmu_alloc_identity_domain(smmu);
> + if (IS_ERR(qsmmu->identity))
> + return PTR_ERR(qsmmu->identity);
> +
> + cbndx = to_smmu_domain(qsmmu->identity)->cfg.cbndx;

I don't really get the point of going through the dance of allocating a
whole iommu_domain() just to get a context. If you don't want to simply
statically reserve a context at probe time, then just allocate from
smmu->context_map here (where AFAICS "here" should be in cfg_probe
anyway). This is entirely driver-internal, so there shouldn't be any
need for IOMMU-API-level stuff to be involved.

Robin.

> +
> + for (i = 0; i < smmu->num_mapping_groups; i++) {
> + smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
> +
> + if (FIELD_GET(ARM_SMMU_SMR_VALID, smr)) {
> + smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
> + smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
> + smmu->smrs[i].valid = true;
> +
> + smmu->s2crs[i].type = S2CR_TYPE_TRANS;
> + smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT;
> + smmu->s2crs[i].cbndx = cbndx;
> + smmu->s2crs[i].count++;
> + }
> + }
> +
> + return 0;
> +}
> +
> static int qcom_smmu_def_domain_type(struct device *dev)
> {
> const struct of_device_id *match =
> @@ -270,6 +302,7 @@ static const struct arm_smmu_impl qcom_smmu_impl = {
> .cfg_probe = qcom_smmu_cfg_probe,
> .def_domain_type = qcom_smmu_def_domain_type,
> .reset = qcom_smmu500_reset,
> + .inherit_mappings = qcom_smmu_inherit_mappings,
> };
>
> static const struct arm_smmu_impl qcom_adreno_smmu_impl = {
>

\
 
 \ /
  Last update: 2020-09-11 19:30    [W:0.431 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site