linux-kernel - Re: [PATCH 0/5] MDSS reg bus interconnect

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Message-ID: <254cd131-4ad1-44c9-2653-862580503c15@linaro.org>
Date:   Mon, 29 May 2023 11:47:17 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Krishna Manikandan <quic_mkrishn@...cinc.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] MDSS reg bus interconnect

On 29/05/2023 10:42, Konrad Dybcio wrote:
> 
> 
> On 29.05.2023 04:42, Dmitry Baryshkov wrote:
>> On Mon, 17 Apr 2023 at 18:30, Konrad Dybcio <konrad.dybcio@...aro.org> 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..
>>>
>>> This series tries to address the lack of that.
>>>
>>> Example path:
>>>
>>> interconnects = <&bimc MASTER_AMPSS_M0 0 &config_noc SLAVE_DISPLAY_CFG 0>;
>>
>> If we are going to touch the MDSS interconnects, could you please also
>> add the rotator interconnect to the bindings?
>> We do not need to touch it at this time, but let's not have to change
>> bindings later again.
>>
> Ack

Also, several points noted from the mdss fbdev driver:

- All possible clents vote for the low bw setting. This includes DSI, 
HDMI, MDSS itself and INTF
- SMMU also casts such vote, which I do not think should be necessary, 
unless there is a separate MDSS SMMU?
- PINGPONG cacsts high bw setting for the sake of speeding up the LUT 
tables if required.

-- 
With best wishes
Dmitry