Re: [PATCH RESEND v17 3/5] iommu/arm-smmu: add support for PRR bit setup

[Bibek Kumar Patro <quic_bibekkum@quicinc.com>]

On 11/20/2024 10:47 PM, Rob Clark wrote:
> On Thu, Nov 14, 2024 at 8:10 AM Bibek Kumar Patro
> <quic_bibekkum@quicinc.com> wrote:
>>
>> Add an adreno-smmu-priv interface for drm/msm to call
>> into arm-smmu-qcom and initiate the PRR bit setup or reset
>> sequence as per request.
>>
>> This will be used by GPU to setup the PRR bit and related
>> configuration registers through adreno-smmu private
>> interface instead of directly poking the smmu hardware.
>>
>> Suggested-by: Rob Clark <robdclark@gmail.com>
>> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@quicinc.com>
>> ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 37 ++++++++++++++++++++++
>>   drivers/iommu/arm/arm-smmu/arm-smmu.h      |  2 ++
>>   include/linux/adreno-smmu-priv.h           | 14 ++++++++
>>   3 files changed, 53 insertions(+)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> index d26f5aea248e..0e4f3fbda961 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> @@ -16,6 +16,8 @@
>>
>>   #define QCOM_DUMMY_VAL -1
>>
>> +#define GFX_ACTLR_PRR          (1 << 5)
>> +
>>   static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
>>   {
>>          return container_of(smmu, struct qcom_smmu, smmu);
>> @@ -99,6 +101,32 @@ static void qcom_adreno_smmu_resume_translation(const void *cookie, bool termina
>>          arm_smmu_cb_write(smmu, cfg->cbndx, ARM_SMMU_CB_RESUME, reg);
>>   }
>>
>> +static void qcom_adreno_smmu_set_prr_bit(const void *cookie, bool set)
>> +{
>> +       struct arm_smmu_domain *smmu_domain = (void *)cookie;
>> +       struct arm_smmu_device *smmu = smmu_domain->smmu;
>> +       struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
>> +       u32 reg = 0;
>> +
>> +       reg =  arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_ACTLR);
>> +       reg &= ~GFX_ACTLR_PRR;
>> +       if (set)
>> +               reg |= FIELD_PREP(GFX_ACTLR_PRR, 1);
>> +       arm_smmu_cb_write(smmu, cfg->cbndx, ARM_SMMU_CB_ACTLR, reg);
>> +}
>> +
>> +static void qcom_adreno_smmu_set_prr_addr(const void *cookie, phys_addr_t page_addr)
>> +{
>> +       struct arm_smmu_domain *smmu_domain = (void *)cookie;
>> +       struct arm_smmu_device *smmu = smmu_domain->smmu;
>> +
>> +       writel_relaxed(lower_32_bits(page_addr),
>> +                               smmu->base + ARM_SMMU_GFX_PRR_CFG_LADDR);
>> +
>> +       writel_relaxed(upper_32_bits(page_addr),
>> +                               smmu->base + ARM_SMMU_GFX_PRR_CFG_UADDR);
>> +}
>> +
>>   #define QCOM_ADRENO_SMMU_GPU_SID 0
>>
>>   static bool qcom_adreno_smmu_is_gpu_device(struct device *dev)
>> @@ -210,6 +238,7 @@ static bool qcom_adreno_can_do_ttbr1(struct arm_smmu_device *smmu)
>>   static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>>                  struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
>>   {
>> +       const struct device_node *np = smmu_domain->smmu->dev->of_node;
>>          struct adreno_smmu_priv *priv;
>>
>>          smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;
>> @@ -239,6 +268,14 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>>          priv->get_fault_info = qcom_adreno_smmu_get_fault_info;
>>          priv->set_stall = qcom_adreno_smmu_set_stall;
>>          priv->resume_translation = qcom_adreno_smmu_resume_translation;
>> +       priv->set_prr_bit = NULL;
>> +       priv->set_prr_addr = NULL;
>> +
>> +       if (of_device_is_compatible(np, "qcom,smmu-500") &&
>> +                       of_device_is_compatible(np, "qcom,adreno-smmu")) {
> 
> fwiw, it seems like PRR actually works on sc7180, which is _not_
> mmu-500, so I guess the support actually goes back further.
> 

As I checked sc7180 was on previous variant of SMMU,
so targets on this variant have different steps to set PRR bit.
<Do not have both prr bit and PRR page registers>.

It's MMU-500 targets only where PRR support is with both PRR bit
and PRR page addr registers. As I was re-visiting our discussions on v13
regarding this - I remember that's why we started using the SMMU-
compatible string based PRR procedure selection instead of the reserved-
memory node. [1] i.e Based on SMMU variant (as selected by compatible
string), specific sequence will be selected.

So for now only MMU-500 based selection has been supported as part of
this series and will add subsequent support for other SMMU-variants
thereafter.

> I'm curious if we can just rely on this being supported by any hw that
> has a6xx or newer?
> 

I'd need to check on targets which will be based on a6xx onwards, on
what will be the procedure planned to support PRR feature. I'll update
the information over this space.

[1]: 
https://lore.kernel.org/all/5790afa3-f9c0-4720-9804-8a7ff3d91854@quicinc.com/#:~:text=%3E%20I%20guess%20if,part%20as%20well.

Thanks & regards,
Bibek

> BR,
> -R
> 
>> +               priv->set_prr_bit = qcom_adreno_smmu_set_prr_bit;
>> +               priv->set_prr_addr = qcom_adreno_smmu_set_prr_addr;
>> +       }
>>
>>          return 0;
>>   }
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
>> index e2aeb511ae90..2dbf3243b5ad 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
>> @@ -154,6 +154,8 @@ enum arm_smmu_cbar_type {
>>   #define ARM_SMMU_SCTLR_M               BIT(0)
>>
>>   #define ARM_SMMU_CB_ACTLR              0x4
>> +#define ARM_SMMU_GFX_PRR_CFG_LADDR     0x6008
>> +#define ARM_SMMU_GFX_PRR_CFG_UADDR     0x600C
>>
>>   #define ARM_SMMU_CB_RESUME             0x8
>>   #define ARM_SMMU_RESUME_TERMINATE      BIT(0)
>> diff --git a/include/linux/adreno-smmu-priv.h b/include/linux/adreno-smmu-priv.h
>> index c637e0997f6d..614665153b3e 100644
>> --- a/include/linux/adreno-smmu-priv.h
>> +++ b/include/linux/adreno-smmu-priv.h
>> @@ -50,6 +50,18 @@ struct adreno_smmu_fault_info {
>>    *                 the GPU driver must call resume_translation()
>>    * @resume_translation: Resume translation after a fault
>>    *
>> + * *CAUTION* : PRR callbacks (set_prr_bit/set_prr_addr) are NULL terminated for
>> + *             targets without PRR support. Exercise caution and verify target
>> + *             capabilities before invoking these callbacks to prevent potential
>> + *             runtime errors or unexpected behavior.
>> + *
>> + * @set_prr_bit:   Extendible interface to be used by GPU to modify the
>> + *                ACTLR register bits, currently used to configure
>> + *                Partially-Resident-Region (PRR) bit for feature's
>> + *                setup and reset sequence as requested.
>> + * @set_prr_addr:  Configure the PRR_CFG_*ADDR register with the
>> + *                physical address of PRR page passed from
>> + *                GPU driver.
>>    *
>>    * The GPU driver (drm/msm) and adreno-smmu work together for controlling
>>    * the GPU's SMMU instance.  This is by necessity, as the GPU is directly
>> @@ -67,6 +79,8 @@ struct adreno_smmu_priv {
>>       void (*get_fault_info)(const void *cookie, struct adreno_smmu_fault_info *info);
>>       void (*set_stall)(const void *cookie, bool enabled);
>>       void (*resume_translation)(const void *cookie, bool terminate);
>> +    void (*set_prr_bit)(const void *cookie, bool set);
>> +    void (*set_prr_addr)(const void *cookie, phys_addr_t page_addr);
>>   };
>>
>>   #endif /* __ADRENO_SMMU_PRIV_H */
>> --
>> 2.34.1
>>