linux-kernel - Re: [PATCH v6 3/7] drm/msm: adreno: dynamically generate GMU bw table

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Message-ID: <f07d9efc-fa3d-44e2-83f5-621ffeaa9f91@oss.qualcomm.com>
Date: Mon, 23 Dec 2024 16:02:15 +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 3/7] drm/msm: adreno: dynamically generate GMU bw table

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, but for
> now we statically fill the bw_table with values from the
> downstream driver.
> 
> Only the first entry is used, which is a disable vote, so we
> currently rely on scaling via the linux interconnect paths.
> 
> Let's dynamically generate the bw_table with the vote values
> previously calculated from the OPPs.
> 
> Those entries will then be used by the GMU when passing the
> appropriate bandwidth level while voting for a gpu frequency.
> 
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---

[...]

> +	/*
> +	 * These are the CX (CNOC) votes - these are used by the GMU
> +	 * The 'CN0' BCM is used on all targets, and votes are basically
> +	 * 'off' and 'on' states with first bit to enable the path.
> +	 */
> +
> +	msg->cnoc_cmds_addrs[0] = cmd_db_read_addr("CN0");
> +	msg->cnoc_cmds_num = 1;
> +
> +	msg->cnoc_cmds_data[0][0] = BCM_TCS_CMD(true, false, 0, 0);
> +	msg->cnoc_cmds_data[1][0] = BCM_TCS_CMD(true, true, 0, BIT(0));
> +
> +	/* Compute the wait bitmask with each BCM having the commit bit */
> +	msg->cnoc_wait_bitmask = 0;
> +	for (j = 0; j < msg->cnoc_cmds_num; j++)
> +		if (msg->cnoc_cmds_data[0][j] & BCM_TCS_CMD_COMMIT_MASK)
> +			msg->cnoc_wait_bitmask |= BIT(j);

Still very much not a fan of this.

I think this would be equally telling:

/* Always flush on/off commands */
msg->cnoc_wait_bitmask = BIT(0);

with or without that:

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

Konrad