linux-kernel - Re: [v1 1/2] clk: qcom: gdsc: Use the default transition delay for GDSCs

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Message-Id: <20220217231916.E944BC340E8@smtp.kernel.org>
Date:   Thu, 17 Feb 2022 15:19:15 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Taniya Das <tdas@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [v1 1/2] clk: qcom: gdsc: Use the default transition delay for GDSCs

Quoting Bjorn Andersson (2022-02-10 11:32:03)
> On Thu 10 Feb 01:28 CST 2022, Stephen Boyd wrote:
> 
> > I'd prefer we invert the logic so that we don't need to litter this flag
> > all over the place. I recall that the wait values were incorrect a long
> > time ago on early gdsc using designs but hopefully they've been fixed
> > now and we can simply use the default power on reset (POR) values.
> 
> Are you suggesting that we make it the default to not update the values
> and then provide means to specify it where needed?

Sure!

> 
> I like that suggestion.
> 
> But as mentioned in my reply yesterday, GPU_CX on several platforms
> needs a different CLK_DIS_WAIT_VAL - and not the same value.
> 
> Are these values ever 0? Or could we simply add the three numbers to
> struct gdsc and have 0 denote "use hw default"?

I don't think they're ever set to zero. That would most likely just
break things because they need a few clk cycles to wait between
transitioning states. Otherwise the GDSC gets stuck and the clks don't
work.