linux-kernel - Re: [PATCH v3 4/7] clk: qcom: hfpll: CLK_IGNORE

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Message-Id: <20191219062521.9CDAD21582@mail.kernel.org>
Date:   Wed, 18 Dec 2019 22:25:20 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Niklas Cassel <niklas.cassel@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, amit.kucheria@...aro.org,
        Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/7] clk: qcom: hfpll: CLK_IGNORE_UNUSED

Quoting Niklas Cassel (2019-11-25 05:59:06)
> From: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
> 
> When COMMON_CLK_DISABLED_UNUSED is set, in an effort to save power and
> to keep the software model of the clock in line with reality, the
> framework transverses the clock tree and disables those clocks that
> were enabled by the firmware but have not been enabled by any device
> driver.
> 
> If CPUFREQ is enabled, early during the system boot, it might attempt
> to change the CPU frequency ("set_rate"). If the HFPLL is selected as
> a provider, it will then change the rate for this clock.
> 
> As boot continues, clk_disable_unused_subtree will run. Since it wont
> find a valid counter (enable_count) for a clock that is actually
> enabled it will attempt to disable it which will cause the CPU to
> stop. Notice that in this driver, calls to check whether the clock is
> enabled are routed via the is_enabled callback which queries the
> hardware.
> 
> The following commit, rather than marking the clock critical and
> forcing the clock to be always enabled, addresses the above scenario
> making sure the clock is not disabled but it continues to rely on the
> firmware to enable the clock.
> 
> Co-developed-by: Niklas Cassel <niklas.cassel@...aro.org>
> Signed-off-by: Niklas Cassel <niklas.cassel@...aro.org>
> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---

Applied to clk-next