linux-kernel - Re: [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS

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Message-ID: <c5cfc132-effb-8269-ac5d-ed8c988d1a16@quicinc.com>
Date:   Wed, 14 Jun 2023 12:54:54 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Marijn Suijten <marijn.suijten@...ainline.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC:     <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        "Jessica Zhang" <quic_jesszhan@...cinc.com>,
        Sean Paul <sean@...rly.run>
Subject: Re: [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS_WIDEN feature flag
 for DPU >= 5.0



On 6/14/2023 12:35 PM, Abhinav Kumar wrote:
> 
> 
> On 6/14/2023 5:23 AM, Marijn Suijten wrote:
>> On 2023-06-14 15:01:59, Dmitry Baryshkov wrote:
>>> On 14/06/2023 14:42, Marijn Suijten wrote:
>>>> On 2023-06-13 18:57:11, Jessica Zhang wrote:
>>>>> DPU 5.x+ supports a databus widen mode that allows more data to be 
>>>>> sent
>>>>> per pclk. Enable this feature flag on all relevant chipsets.
>>>>>
>>>>> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
>>>>> ---
>>>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c | 3 ++-
>>>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h | 2 ++
>>>>>    2 files changed, 4 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c 
>>>>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
>>>>> index 36ba3f58dcdf..0be7bf0bfc41 100644
>>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
>>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
>>>>> @@ -103,7 +103,8 @@
>>>>>        (BIT(DPU_INTF_INPUT_CTRL) | \
>>>>>         BIT(DPU_INTF_TE) | \
>>>>>         BIT(DPU_INTF_STATUS_SUPPORTED) | \
>>>>> -     BIT(DPU_DATA_HCTL_EN))
>>>>> +     BIT(DPU_DATA_HCTL_EN) | \
>>>>> +     BIT(DPU_INTF_DATABUS_WIDEN))
>>>>
>>>> This doesn't work.  DPU 5.0.0 is SM8150, which has DSI 6G 2.3.  In the
>>>> last patch for DSI you state and enable widebus for DSI 6G 2.5+ only,
>>>> meaning DPU and DSI are now desynced, and the output is completely
>>>> corrupted.
>>
>> Tested this on SM8350 which actually has DSI 2.5, and it is also
>> corrupted with this series so something else on this series might be
>> broken.
>>

Missed this response. That seems strange.

This series was tested on SM8350 HDK with a command mode panel.

We will fix the DPU-DSI handshake and post a v2 but your issue needs 
investigation in parallel.

So another bug to track that would be great.

>>>> Is the bound in dsi_host wrong, or do DPU and DSI need to communicate
>>>> when widebus will be enabled, based on DPU && DSI supporting it?
>>>
>>> I'd prefer to follow the second approach, as we did for DP. DPU asks the
>>> actual video output driver if widebus is to be enabled.
>>
> 
> I was afraid of this. This series was made on an assumption that the DPU 
> version of widebus and DSI version of widebus would be compatible but 
> looks like already SM8150 is an outlier.
> 
> Yes, I think we have to go with second approach.
> 
> DPU queries DSI if it supports widebus and enables it.
> 
> Thanks for your responses. We will post a v2.
> 
>> Doesn't it seem very strange that DPU 5.x+ comes with a widebus feature,
>> but the DSI does not until two revisions later?  Or is this available on
>> every interface, but only for a different (probably DP) encoder block?
>>
> 
> Yes its strange.
> 
>> - Marijn