From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Andersson Subject: Re: [PATCH 08/13] clk: qcom: hfpll: CLK_IGNORE_UNUSED Date: Wed, 16 Jan 2019 22:33:12 -0800 Message-ID: <20190117063312.GE25498@builder> References: <1545039990-19984-1-git-send-email-jorge.ramirez-ortiz@linaro.org> <1545039990-19984-9-git-send-email-jorge.ramirez-ortiz@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1545039990-19984-9-git-send-email-jorge.ramirez-ortiz@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: Jorge Ramirez-Ortiz Cc: robh+dt@kernel.org, mark.rutland@arm.com, andy.gross@linaro.org, david.brown@linaro.org, sboyd@kernel.org, will.deacon@arm.com, mturquette@baylibre.com, jassisinghbrar@gmail.com, vkoul@kernel.org, niklas.cassel@linaro.org, sibis@codeaurora.org, georgi.djakov@linaro.org, arnd@arndb.de, horms+renesas@verge.net.au, heiko@sntech.de, enric.balletbo@collabora.com, jagan@amarulasolutions.com, olof@lixom.net, amit.kucheria@linaro.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org List-Id: devicetree@vger.kernel.org On Mon 17 Dec 01:46 PST 2018, 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. Notice that in this driver, calls to check whether the clock is > enabled are routed via the is_enabled callback which queries the > hardware. > With the CPUFREQ referencing the CPU clock driver, that has decided to run off this clock, why is it not refcounted? Regards, Bjorn > 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 > Signed-off-by: Niklas Cassel > Signed-off-by: Jorge Ramirez-Ortiz > --- > drivers/clk/qcom/hfpll.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/clk/qcom/hfpll.c b/drivers/clk/qcom/hfpll.c > index 0ffed0d..9d92f5d 100644 > --- a/drivers/clk/qcom/hfpll.c > +++ b/drivers/clk/qcom/hfpll.c > @@ -58,6 +58,7 @@ static int qcom_hfpll_probe(struct platform_device *pdev) > .parent_names = (const char *[]){ "xo" }, > .num_parents = 1, > .ops = &clk_ops_hfpll, > + .flags = CLK_IGNORE_UNUSED, > }; > > h = devm_kzalloc(dev, sizeof(*h), GFP_KERNEL); > -- > 2.7.4 >