On 1/22/19 19:47, Stephen Boyd wrote: > Quoting Jorge Ramirez (2019-01-17 02:46:21) >> On 1/17/19 11:08, Viresh Kumar wrote: >>> 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 :) >> >> ah, of course, sorry was over-thinking this thing :) >> >>> >>> 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. >>> >> >> since this clock is enabled by the firmware, it seems to me that using >> CLK_IGNORE_UNUSED remains the best option. >> > > What do you do about CPUs being offlined? Presumably when the CPU is > gone the system doesn't need to keep the clk enabled anymore. > > the kernel does not take any action - it is under firmware control; and since the clock is shared between all cores I there will have to be some involvement not only at TF-A/firmware level but also at the TrustedOS level for when the last core is offlined. I dont have visibility on either of those projects though.
