From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Cc: sboyd@kernel.org, david.brown@linaro.org,
jassisinghbrar@gmail.com, mark.rutland@arm.com,
mturquette@baylibre.com, robh+dt@kernel.org, will.deacon@arm.com,
arnd@arndb.de, horms+renesas@verge.net.au, heiko@sntech.de,
sibis@codeaurora.org, enric.balletbo@collabora.com,
jagan@amarulasolutions.com, olof@lixom.net, vkoul@kernel.org,
niklas.cassel@linaro.org, georgi.djakov@linaro.org,
amit.kucheria@linaro.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
linux-arm-msm@vger.kernel.org, khasim.mohammed@linaro.org
Subject: Re: [PATCH v3 08/14] clk: qcom: hfpll: CLK_IGNORE_UNUSED
Date: Thu, 11 Jul 2019 08:16:31 -0700 [thread overview]
Message-ID: <20190711151631.GI7234@tuxbook-pro> (raw)
In-Reply-To: <20190625164733.11091-9-jorge.ramirez-ortiz@linaro.org>
On Tue 25 Jun 09:47 PDT 2019, Jorge Ramirez-Ortiz wrote:
> 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.
But if CPUfreq has acquired the CPU clock and the hfpll is the currently
selected input, why does the clock framework not know about this clock
being used?
> 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@linaro.org>
> Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>
> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
I can see that we have a real issue in the case where CPUfreq is not
enabled and hence there are no clients, according to Linux. And that I
don't know another way to guard against.
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Regards,
Bjorn
> ---
> drivers/clk/qcom/hfpll.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/clk/qcom/hfpll.c b/drivers/clk/qcom/hfpll.c
> index 0ffed0d41c50..d5fd27938e7b 100644
> --- a/drivers/clk/qcom/hfpll.c
> +++ b/drivers/clk/qcom/hfpll.c
> @@ -58,6 +58,13 @@ static int qcom_hfpll_probe(struct platform_device *pdev)
> .parent_names = (const char *[]){ "xo" },
> .num_parents = 1,
> .ops = &clk_ops_hfpll,
> + /*
> + * rather than marking the clock critical and forcing the clock
> + * to be always enabled, we make sure that the clock is not
> + * disabled: the firmware remains responsible of enabling this
> + * clock (for more info check the commit log)
> + */
> + .flags = CLK_IGNORE_UNUSED,
> };
>
> h = devm_kzalloc(dev, sizeof(*h), GFP_KERNEL);
> --
> 2.21.0
>
next prev parent reply other threads:[~2019-07-11 15:15 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 16:47 [PATCH v3 00/14] Support CPU frequency scaling on QCS404 Jorge Ramirez-Ortiz
2019-06-25 16:47 ` [PATCH v3 01/14] clk: qcom: gcc: limit GPLL0_AO_OUT operating frequency Jorge Ramirez-Ortiz
2019-07-11 15:30 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 02/14] mbox: qcom: add APCS child device for QCS404 Jorge Ramirez-Ortiz
2019-07-11 14:44 ` Bjorn Andersson
2019-07-31 14:10 ` Jorge Ramirez
2019-06-25 16:47 ` [PATCH v3 03/14] mbox: qcom: replace integer with valid macro Jorge Ramirez-Ortiz
2019-07-11 14:37 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 04/14] dt-bindings: mailbox: qcom: Add clock-name optional property Jorge Ramirez-Ortiz
2019-07-11 14:45 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 05/14] clk: qcom: apcs-msm8916: get parent clock names from DT Jorge Ramirez-Ortiz
2019-07-11 14:58 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 06/14] clk: qcom: hfpll: " Jorge Ramirez-Ortiz
2019-07-11 15:07 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 07/14] clk: qcom: hfpll: register as clock provider Jorge Ramirez-Ortiz
2019-07-11 15:07 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 08/14] clk: qcom: hfpll: CLK_IGNORE_UNUSED Jorge Ramirez-Ortiz
2019-07-11 15:16 ` Bjorn Andersson [this message]
2019-07-31 14:30 ` Jorge Ramirez
2019-06-25 16:47 ` [PATCH v3 09/14] arm64: dts: qcom: msm8916: Add the clocks for the APCS mux/divider Jorge Ramirez-Ortiz
2019-07-11 15:24 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 10/14] arm64: dts: qcom: qcs404: Add OPP table Jorge Ramirez-Ortiz
2019-07-11 15:25 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 11/14] arm64: dts: qcom: qcs404: Add HFPLL node Jorge Ramirez-Ortiz
2019-07-11 15:25 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 12/14] arm64: dts: qcom: qcs404: Add the clocks for APCS mux/divider Jorge Ramirez-Ortiz
2019-07-11 15:27 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 13/14] arm64: dts: qcom: qcs404: Add DVFS support Jorge Ramirez-Ortiz
2019-06-26 9:08 ` Niklas Cassel
2019-06-26 9:10 ` Niklas Cassel
2019-07-11 15:29 ` Bjorn Andersson
2019-06-25 16:47 ` [PATCH v3 14/14] arm64: defconfig: Enable HFPLL Jorge Ramirez-Ortiz
2019-07-11 15:27 ` Bjorn Andersson
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