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

[Abhinav Kumar]

On 6/15/2022 11:42 AM, Dmitry Baryshkov wrote:
> 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.
> 
Alright, agreed

Reviewed-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
>>
>> 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);
> 
>