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

From: Konrad Dybcio
Date: Mon May 29 2023 - 05:09:18 EST

On 29.05.2023 10:47, Dmitry Baryshkov wrote:
> 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@xxxxxxxxxx> 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
As in, "you need NUM_CLIENTS * MIN_VOTE" or as in "any client necessitates
a vote"?

> - SMMU also casts such vote, which I do not think should be necessary, unless there is a separate MDSS SMMU?
There's one on 8996, pre-845 SoCs often have a MMSS MMU, 845 and
later have a MMSS-specific TBU which (theoretically) requires a
vote for access to 0x400-0x7ff SIDs

> - PINGPONG cacsts high bw setting for the sake of speeding up the LUT tables if required.
Hm, I think is would be a separate topic.