linux-kernel - Re: [PATCH 08/13] clk: qcom: hfpll: CLK_IGNORE

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Date:   Thu, 17 Jan 2019 15:38:07 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Jorge Ramirez <jorge.ramirez-ortiz@...aro.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>, robh+dt@...nel.org,
        mark.rutland@....com, andy.gross@...aro.org,
        david.brown@...aro.org, sboyd@...nel.org, will.deacon@....com,
        mturquette@...libre.com, jassisinghbrar@...il.com,
        vkoul@...nel.org, niklas.cassel@...aro.org, sibis@...eaurora.org,
        georgi.djakov@...aro.org, arnd@...db.de,
        horms+renesas@...ge.net.au, heiko@...ech.de,
        enric.balletbo@...labora.com, jagan@...rulasolutions.com,
        olof@...om.net, amit.kucheria@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH 08/13] clk: qcom: hfpll: CLK_IGNORE_UNUSED

On 17-01-19, 09:38, Jorge Ramirez wrote:
> COMMON_CLK_DISABLED_UNUSED relies on the enable_count reference counter
> to disable the clocks that were enabled by the firwmare and not by the
> drivers.
> 
> the cpufreq driver does not enable the cpu clock.
> 
> so when clk_change_rate is called, the enable_count counter is not
> incremented and therefore it just remains null since this was enabled by
> the firmware.
> 
> I tried doing:
> 
> diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
> index e58bfcb..5a9f83e 100644
> --- a/drivers/cpufreq/cpufreq-dt.c
> +++ b/drivers/cpufreq/cpufreq-dt.c
> @@ -124,6 +124,10 @@ static int resources_available(void)
>                 return ret;
>         }
> 
> + ret = clk_prepare_enable(cpu_clk);
> + if (ret)
> +         return ret;
> +
>         clk_put(cpu_clk);
> 
>         name = find_supply_name(cpu_dev);
> 
> 
> and that removed the need for CLK_IGNORE_UNUSED. But I am not sure of
> the system wide consequences of that change to cpufreq.

If the cpufreq driver enables it then it should disable it on exit as
well, right ? And in that case if you unload your driver's module, you
will hang the system as the clock will get disabled :)

Every other platform must either be marking it with CLK_IGNORE_UNUSED
or they must be doing clk_enable from somewhere, maybe the CPU online
path, not sure though.

-- 
viresh