| Message ID | 20190826164510.6425-5-jorge.ramirez-ortiz@linaro.org (mailing list archive) |
|---|---|
| State | Awaiting Upstream, archived |
| Headers | show |
| Series | [1/5] clk: qcom: gcc: limit GPLL0_AO_OUT operating frequency | expand |
Quoting Jorge Ramirez-Ortiz (2019-08-26 09:45:10) > 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@linaro.org> > Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org> > Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org> > Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> > --- Also this one. Seems fine to merge immediately vs the ones that do some DT trickery.
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);
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@linaro.org> Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> --- drivers/clk/qcom/hfpll.c | 7 +++++++ 1 file changed, 7 insertions(+)