Re: [Freedreno] [PATCH 5/5] drm/msm/dpu1: Handle the reg bus ICC path

[Jeykumar Sankaran <quic_jeykumar@quicinc.com>]

On 4/19/2023 12:48 PM, Konrad Dybcio wrote:
> 
> 
> On 19.04.2023 21:06, Jeykumar Sankaran wrote:
>>
>>
>> On 4/17/2023 8:30 AM, Konrad Dybcio wrote:
>>> Apart from the already handled data bus (MAS_MDP_Pn<->DDR), there's
>>> another path that needs to be handled to ensure MDSS functions properly,
>>> namely the "reg bus", a.k.a the CPU-MDSS interconnect.
>>>
>>> Gating that path may have a variety of effects.. from none to otherwise
>>> inexplicable DSI timeouts..
>>>
>>> On the DPU side, we need to keep the bus alive. The vendor driver
>>> kickstarts it to max (300Mbps) throughput on first commit, but in
>>> exchange for some battery life in rare DPU-enabled-panel-disabled
>>> usecases, we can request it at DPU init and gate it at suspend.
>>>
>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>>> ---
>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 22 ++++++++++++++++++++--
>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h |  1 +
>>>    2 files changed, 21 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>> index dd6c1c40ab9e..d1f77faebbc0 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>> @@ -384,15 +384,17 @@ static int dpu_kms_global_obj_init(struct dpu_kms *dpu_kms)
>>>        return 0;
>>>    }
>>>    -static int dpu_kms_parse_data_bus_icc_path(struct dpu_kms *dpu_kms)
>>> +static int dpu_kms_parse_icc_paths(struct dpu_kms *dpu_kms)
>>>    {
>>>        struct icc_path *path0;
>>>        struct icc_path *path1;
>>> +    struct icc_path *reg_bus_path;
>>>        struct drm_device *dev = dpu_kms->dev;
>>>        struct device *dpu_dev = dev->dev;
>>>          path0 = msm_icc_get(dpu_dev, "mdp0-mem");
>>>        path1 = msm_icc_get(dpu_dev, "mdp1-mem");
>>> +    reg_bus_path = msm_icc_get(dpu_dev, "cpu-cfg");
>>>          if (IS_ERR_OR_NULL(path0))
>>>            return PTR_ERR_OR_ZERO(path0);
>>> @@ -404,6 +406,10 @@ static int dpu_kms_parse_data_bus_icc_path(struct dpu_kms *dpu_kms)
>>>            dpu_kms->mdp_path[1] = path1;
>>>            dpu_kms->num_mdp_paths++;
>>>        }
>>> +
>>> +    if (!IS_ERR_OR_NULL(reg_bus_path))
>>> +        dpu_kms->reg_bus_path = reg_bus_path;
>>> +
>>>        return 0;
>>>    }
>>>    @@ -1039,7 +1045,7 @@ static int dpu_kms_hw_init(struct msm_kms *kms)
>>>            DPU_DEBUG("REG_DMA is not defined");
>>>        }
>>>    -    dpu_kms_parse_data_bus_icc_path(dpu_kms);
>>> +    dpu_kms_parse_icc_paths(dpu_kms);
>>>          rc = pm_runtime_resume_and_get(&dpu_kms->pdev->dev);
>>>        if (rc < 0)
>>> @@ -1241,6 +1247,9 @@ static int __maybe_unused dpu_runtime_suspend(struct device *dev)
>>>        for (i = 0; i < dpu_kms->num_mdp_paths; i++)
>>>            icc_set_bw(dpu_kms->mdp_path[i], 0, 0);
>>>    +    if (dpu_kms->reg_bus_path)
>>> +        icc_set_bw(dpu_kms->reg_bus_path, 0, 0);
>>> +
>>>        return 0;
>>>    }
>>>    @@ -1261,6 +1270,15 @@ static int __maybe_unused dpu_runtime_resume(struct device *dev)
>>>            return rc;
>>>        }
>>>    +    /*
>>> +     * The vendor driver supports setting 76.8 / 150 / 300 Mbps on this
>> How do you arrive at these distint BW values? Are they provided by the ICC fwk for the given path?
> They're hardcoded in the SDE driver.
> 
> Konrad
These bandwidths are derived from the scaling frequencies of all the 
buses participating in the icc-path. So they cannot be constants. 
Ideally they should be read from the hw catalog data of the respective 
platform.

Jeykumar S.
>>> +     * path, but it seems to go for the highest level when display output
>>> +     * is enabled and zero otherwise. For simplicity, we can assume that
>>> +     * DPU being enabled and running implies that.
>>> +     */
>>> +    if (dpu_kms->reg_bus_path)
>>> +        icc_set_bw(dpu_kms->reg_bus_path, 0, MBps_to_icc(300));
>>> +
>>>        dpu_vbif_init_memtypes(dpu_kms);
>>>          drm_for_each_encoder(encoder, ddev)
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
>>> index d5d9bec90705..c332381d58c4 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
>>> @@ -111,6 +111,7 @@ struct dpu_kms {
>>>        atomic_t bandwidth_ref;
>>>        struct icc_path *mdp_path[2];
>>>        u32 num_mdp_paths;
>>> +    struct icc_path *reg_bus_path;
>>>    };
>>>      struct vsync_info {
>>>