linux-kernel - Re: [PATCH] opp: Provide a function for just setting bandwidth

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Date:   Mon, 29 May 2023 10:28:54 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] opp: Provide a function for just setting bandwidth

On 26-05-23, 12:59, Konrad Dybcio wrote:
> There are some users which have tight power sequencing requirements,
> like the Qualcomm Adreno GPU.
> 
> Dropping the entire OPP kills clocks, bw and required-opps at once,
> but on certain Adrenos we need something like:
> 
> 
> disable memory clock (clk)
> disable all other clocks, including the opp-managed core clock (clk_bulk)
> kill one, fully manually controlled genpd (manual runtime pm)
> remove bus vote (func proposed in this patch)
> kill another genpd (manual runtime pm)
> kill the opp-managed genpd (automatic pm calls)
> 
> Changing the order kills the chip until you reboot the whole board and
> setting freq=0 using dev_pm_opp_set_rate doesn't drop the bw vote.

I am a bit confused now.

What's the exact problem with dev_pm_opp_set_rate(dev, 0) ? It does set the
bandwidth too, from what I can see.

-- 
viresh