linux-kernel - Re: [PATCH v6 2/7] drm/msm: adreno: add plumbing to generate bandwidth vote table for GMU

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Message-ID: <5b1fa9a3-de58-4ad2-aaf4-f239f7c60ec8@oss.qualcomm.com>
Date: Mon, 23 Dec 2024 15:54:14 +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 2/7] drm/msm: adreno: add plumbing to generate
 bandwidth vote table for GMU

On 17.12.2024 3:51 PM, Neil Armstrong wrote:
> The Adreno GPU Management Unit (GMU) can also scale DDR Bandwidth along
> the Frequency and Power Domain level, but by default we leave the
> OPP core scale the interconnect ddr path.
> 
> While scaling via the interconnect path was sufficient, newer GPUs
> like the A750 requires specific vote paremeters and bandwidth to
> achieve full functionality.
> 
> In order to calculate vote values used by the GPU Management
> Unit (GMU), we need to parse all the possible OPP Bandwidths and
> create a vote value to be sent to the appropriate Bus Control
> Modules (BCMs) declared in the GPU info struct.
> 
> This vote value is called IB, while on the other side 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 vote will be calculated later when setting the frequency.
> 
> The vote array will then be used to dynamically generate the GMU
> bw_table sent during the GMU power-up.
> 
> 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