Re: [PATCH 5/5] iommu/arm-smmu: Setup identity domain for boot mappings

[Laurentiu Tudor <laurentiu.tudor@nxp.com>]

On 7/9/2020 10:57 PM, Bjorn Andersson wrote:
> On Thu 09 Jul 08:50 PDT 2020, Laurentiu Tudor wrote:
> 
>>
>>
>> On 7/9/2020 8:01 AM, 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>
>>> ---
>>>  drivers/iommu/arm-smmu-qcom.c | 11 +++++
>>>  drivers/iommu/arm-smmu.c      | 80 +++++++++++++++++++++++++++++++++--
>>>  drivers/iommu/arm-smmu.h      |  3 ++
>>>  3 files changed, 90 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
>>> index 86b1917459a4..397df27c1d69 100644
>>> --- a/drivers/iommu/arm-smmu-qcom.c
>>> +++ b/drivers/iommu/arm-smmu-qcom.c
>>> @@ -26,6 +26,7 @@ static const struct of_device_id qcom_smmu_client_of_match[] = {
>>>  static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
>>>  {
>>>  	unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1);
>>> +	u32 smr;
>>>  	u32 reg;
>>>  	int i;
>>>  
>>> @@ -56,6 +57,16 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
>>>  		}
>>>  	}
>>>  
>>> +	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;
>>> +		}
>>> +	}
>>> +
>>>  	return 0;
>>>  }
>>>  
>>> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>>> index e2d6c0aaf1ea..a7cb27c1a49e 100644
>>> --- a/drivers/iommu/arm-smmu.c
>>> +++ b/drivers/iommu/arm-smmu.c
>>> @@ -652,7 +652,8 @@ static void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
>>>  }
>>>  
>>>  static int arm_smmu_init_domain_context(struct iommu_domain *domain,
>>> -					struct arm_smmu_device *smmu)
>>> +					struct arm_smmu_device *smmu,
>>> +					bool boot_domain)
>>>  {
>>>  	int irq, start, ret = 0;
>>>  	unsigned long ias, oas;
>>> @@ -770,6 +771,15 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
>>>  		ret = -EINVAL;
>>>  		goto out_unlock;
>>>  	}
>>> +
>>> +	/*
>>> +	 * Use the last context bank for identity mappings during boot, to
>>> +	 * avoid overwriting in-use bank configuration while we're setting up
>>> +	 * the new mappings.
>>> +	 */
>>> +	if (boot_domain)
>>> +		start = smmu->num_context_banks - 1;
>>> +
>>>  	ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,
>>>  				      smmu->num_context_banks);
>>>  	if (ret < 0)
>>> @@ -1149,7 +1159,10 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>>>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>>>  	struct arm_smmu_master_cfg *cfg;
>>>  	struct arm_smmu_device *smmu;
>>> +	bool free_identity_domain = false;
>>> +	int idx;
>>>  	int ret;
>>> +	int i;
>>>  
>>>  	if (!fwspec || fwspec->ops != &arm_smmu_ops) {
>>>  		dev_err(dev, "cannot attach to SMMU, is it on the same bus?\n");
>>> @@ -1174,7 +1187,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>>>  		return ret;
>>>  
>>>  	/* Ensure that the domain is finalised */
>>> -	ret = arm_smmu_init_domain_context(domain, smmu);
>>> +	ret = arm_smmu_init_domain_context(domain, smmu, false);
>>>  	if (ret < 0)
>>>  		goto rpm_put;
>>>  
>>> @@ -1190,9 +1203,34 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>>>  		goto rpm_put;
>>>  	}
>>>  
>>> +	/* Decrement use counter for any references to the identity domain */
>>> +	mutex_lock(&smmu->stream_map_mutex);
>>> +	if (smmu->identity) {
>>> +		struct arm_smmu_domain *identity = to_smmu_domain(smmu->identity);
>>> +
>>> +		for_each_cfg_sme(cfg, fwspec, i, idx) {
>>> +			dev_err(smmu->dev, "%s() %#x\n", __func__, smmu->smrs[idx].id);
>>
>> Debug leftovers?
>>
> 
> Indeed.
> 
>> Apart from that I plan to give this a go on some NXP chips. Will keep
>> you updated.
>>
> 
> Thanks, I'm expecting that all you need is the first patch in the series
> and some impl specific cfg_probe that sets up (or read back) the
> relevant SMRs and mark them valid.
> 

I finally managed to give a go to the v2 of this patchset and tested it
on a NXP LS2088A chip with the diff [1] below, so please feel free to add:

Tested-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>

Now a question for the SMMU folks: would the approach in the diff below
be acceptable?

[1]

--- a/drivers/iommu/arm-smmu-impl.c
+++ b/drivers/iommu/arm-smmu-impl.c
@@ -102,6 +102,32 @@ static struct arm_smmu_device
*cavium_smmu_impl_init(struct arm_smmu_device *smm
        return &cs->smmu;
 }

+static int nxp_cfg_probe(struct arm_smmu_device *smmu)
+{
+       int i, cnt = 0;
+       u32 smr;
+
+       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;
+
+                       cnt++;
+               }
+       }
+
+       dev_notice(smmu->dev, "\tpreserved %d boot mapping%s\n", cnt,
+                  cnt == 1 ? "" : "s");
+
+       return 0;
+}
+
+static const struct arm_smmu_impl nxp_impl = {
+       .cfg_probe = nxp_cfg_probe,
+};

 #define ARM_MMU500_ACTLR_CPRE          (1 << 1)

@@ -171,6 +197,9 @@ struct arm_smmu_device *arm_smmu_impl_init(struct
arm_smmu_device *smmu)
        if (of_property_read_bool(np, "calxeda,smmu-secure-config-access"))
                smmu->impl = &calxeda_impl;

+       if (of_property_read_bool(np, "nxp,keep-bypass-mappings"))
+               smmu->impl = &nxp_impl;
+
        if (of_device_is_compatible(np, "qcom,sdm845-smmu-500") ||
            of_device_is_compatible(np, "qcom,sc7180-smmu-500"))
                return qcom_smmu_impl_init(smmu);

---
Thanks & Best Regards, Laurentiu
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