linux-kernel - Re: [PATCH v6 4/7] drm/msm: adreno: find bandwidth index of OPP and set it along freq index

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Message-ID: <b1a313b0-fe0e-4612-b555-5708b854ecc2@oss.qualcomm.com>
Date: Mon, 23 Dec 2024 15:50:46 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 4/7] drm/msm: adreno: find bandwidth index of OPP and
 set it along freq index

On 17.12.2024 3:51 PM, Neil Armstrong wrote:
> The Adreno GPU Management Unit (GMU) can also scale the DDR Bandwidth
> along the Frequency and Power Domain level, until now we left the OPP
> core scale the OPP bandwidth via the interconnect path.
> 
> In order to enable bandwidth voting via the GPU Management
> Unit (GMU), when an opp is set by devfreq we also look for
> the corresponding bandwidth index in the previously generated
> bw_table and pass this value along the frequency index to the GMU.
> 
> The GMU also takes another vote called AB which is a 16bit quantized
> value of the floor bandwidth against the maximum supported bandwidth.
> 
> The AB is calculated with a default 25% of the bandwidth like the
> downstream implementation too inform the GMU firmware the minimal
> quantity of bandwidth we require for this OPP. Only pass the AB
> vote starting from A750 GPUs.
> 
> Since we now vote for all resources via the GMU, setting the OPP
> is no more needed, so we can completely skip calling
> dev_pm_opp_set_opp() in this situation.
> 
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Reviewed-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---

Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>

Konrad

>  
> +#define AB_VOTE_MASK		GENMASK(31, 16)
> +#define MAX_AB_VOTE		(FIELD_MAX(AB_VOTE_MASK) - 1)

I'm just not 1000% sure about this -1 here

Konrad