Re: [Freedreno] [PATCH 2/2] drm/msm/a6xx: Create an A6XX GPU specific address space

[Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>]

On 2021-01-20 21:48, Rob Clark wrote:
> On Mon, Jan 11, 2021 at 4:04 AM Sai Prakash Ranjan
> <saiprakash.ranjan@codeaurora.org> wrote:
>> 
>> A6XX GPUs have support for last level cache(LLC) also known
>> as system cache and need to set the bus attributes to
>> use it. Currently we use a generic adreno iommu address space
>> implementation which are also used by older GPU generations
>> which do not have LLC and might introduce issues accidentally
>> and is not clean in a way that anymore additions of GPUs
>> supporting LLC would have to be guarded under ifdefs. So keep
>> the generic code separate and make the address space creation
>> A6XX specific. We also have a helper to set the llc attributes
>> so that if the newer GPU generations do support them, we can
>> use it instead of open coding domain attribute setting for each
>> GPU.
>> 
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
>> ---
>>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c   | 46 
>> ++++++++++++++++++++++++-
>>  drivers/gpu/drm/msm/adreno/adreno_gpu.c | 23 +++++--------
>>  drivers/gpu/drm/msm/adreno/adreno_gpu.h |  7 ++--
>>  3 files changed, 55 insertions(+), 21 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c 
>> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> index 3b798e883f82..3c7ad51732bb 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> @@ -1239,6 +1239,50 @@ static unsigned long a6xx_gpu_busy(struct 
>> msm_gpu *gpu)
>>         return (unsigned long)busy_time;
>>  }
>> 
>> +static struct msm_gem_address_space *
>> +a6xx_create_address_space(struct msm_gpu *gpu, struct platform_device 
>> *pdev)
>> +{
>> +       struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>> +       struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
>> +       struct iommu_domain *iommu;
>> +       struct msm_mmu *mmu;
>> +       struct msm_gem_address_space *aspace;
>> +       u64 start, size;
>> +
>> +       iommu = iommu_domain_alloc(&platform_bus_type);
>> +       if (!iommu)
>> +               return NULL;
>> +
>> +       /*
>> +        * This allows GPU to set the bus attributes required to use 
>> system
>> +        * cache on behalf of the iommu page table walker.
>> +        */
>> +       if (!IS_ERR_OR_NULL(a6xx_gpu->htw_llc_slice))
>> +               adreno_set_llc_attributes(iommu);
>> +
>> +       mmu = msm_iommu_new(&pdev->dev, iommu);
>> +       if (IS_ERR(mmu)) {
>> +               iommu_domain_free(iommu);
>> +               return ERR_CAST(mmu);
>> +       }
>> +
>> +       /*
>> +        * Use the aperture start or SZ_16M, whichever is greater. 
>> This will
>> +        * ensure that we align with the allocated pagetable range 
>> while still
>> +        * allowing room in the lower 32 bits for GMEM and whatnot
>> +        */
>> +       start = max_t(u64, SZ_16M, iommu->geometry.aperture_start);
>> +       size = iommu->geometry.aperture_end - start + 1;
>> +
>> +       aspace = msm_gem_address_space_create(mmu, "gpu",
>> +               start & GENMASK_ULL(48, 0), size);
>> +
>> +       if (IS_ERR(aspace) && !IS_ERR(mmu))
>> +               mmu->funcs->destroy(mmu);
>> +
>> +       return aspace;
>> +}
>> +
>>  static struct msm_gem_address_space *
>>  a6xx_create_private_address_space(struct msm_gpu *gpu)
>>  {
>> @@ -1285,7 +1329,7 @@ static const struct adreno_gpu_funcs funcs = {
>>                 .gpu_state_get = a6xx_gpu_state_get,
>>                 .gpu_state_put = a6xx_gpu_state_put,
>>  #endif
>> -               .create_address_space = 
>> adreno_iommu_create_address_space,
>> +               .create_address_space = a6xx_create_address_space,
>>                 .create_private_address_space = 
>> a6xx_create_private_address_space,
>>                 .get_rptr = a6xx_get_rptr,
>>         },
>> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c 
>> b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>> index b35914de1b27..0f184c3dd9d9 100644
>> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>> @@ -186,11 +186,18 @@ int adreno_zap_shader_load(struct msm_gpu *gpu, 
>> u32 pasid)
>>         return zap_shader_load_mdt(gpu, adreno_gpu->info->zapfw, 
>> pasid);
>>  }
>> 
>> +void adreno_set_llc_attributes(struct iommu_domain *iommu)
>> +{
>> +       struct io_pgtable_domain_attr pgtbl_cfg;
>> +
>> +       pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_ARM_OUTER_WBWA;
> 
> btw, since quirks is the only field in the struct currently, this is
> ok.  But better practice to do something like:
> 
>         struct io_pgtable_domain_attr pgtbl_cfg = {
>                 .quirks = IO_PGTABLE_QUIRK_ARM_OUTER_WBWA,
>         };
> 
> which will zero-initialize any additional fields which might be added
> later, rather than inherit random garbage from the stack.
> 

Right, I will correct this.

Thanks,
Sai

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