[Freedreno] [PATCH v2 1/5] drm/msm/dpu: check both DPU and MDSS devices for the IOMMU

[Dmitry Baryshkov]

On 15/06/2022 20:55, Abhinav Kumar wrote:
> 
> 
> On 5/4/2022 5:16 PM, Dmitry Baryshkov wrote:
>> Follow the lead of MDP5 driver and check both DPU and MDSS devices for
>> the IOMMU specifiers.
>>
>> Historically DPU devices had IOMMU specified in the MDSS device tree
>> node, but as some of MDP5 devices are being converted to the supported
>> by the DPU driver, the driver should adapt and check both devices.
>>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 14 +++++++++++---
>>   1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> index 143d6643be53..5ccda0766f6c 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> @@ -1004,14 +1004,22 @@ static int _dpu_kms_mmu_init(struct dpu_kms 
>> *dpu_kms)
>>       struct msm_mmu *mmu;
>>       struct device *dpu_dev = dpu_kms->dev->dev;
>>       struct device *mdss_dev = dpu_dev->parent;
>> +    struct device *iommu_dev;
>>       domain = iommu_domain_alloc(&platform_bus_type);
>>       if (!domain)
>>           return 0;
>> -    /* IOMMUs are a part of MDSS device tree binding, not the
>> -     * MDP/DPU device. */
>> -    mmu = msm_iommu_new(mdss_dev, domain);
>> +    /*
>> +     * IOMMUs can be a part of MDSS device tree binding, or the
>> +     * MDP/DPU device.
>> +     */
> 
> Can you please explain this a little more?
> 
> So even if some of the mdp5 devices are getting converted to use DPU 
> driver, their device trees are also updated right?

No. The DT describes the device, not the Linux drivers. So while 
updating the drivers we should not change the DT.

> 
> In other words, if DPU driver was using mdss_dev to initialize the 
> iommu, why should the new devices which are going to use DPU have the 
> binding in the dpu_dev?
> 
> 
>> +    if (dev_iommu_fwspec_get(dpu_dev))
>> +        iommu_dev = dpu_dev;
>> +    else
>> +        iommu_dev = mdss_dev;
>> +
>> +    mmu = msm_iommu_new(iommu_dev, domain);
>>       if (IS_ERR(mmu)) {
>>           iommu_domain_free(domain);
>>           return PTR_ERR(mmu);


-- 
With best wishes
Dmitry