Messages in this thread Patch in this message |  | | From | "Rafael J. Wysocki" <> | Date | Tue, 10 Mar 2020 09:37:14 +0100 | Subject | Re: [PATCH v3] intel_idle: Add Comet Lake support |
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On Mon, Mar 9, 2020 at 10:07 AM Pan, Harry <harry.pan@intel.com> wrote: > > Hi Rafael, > > Thanks for the comments. > I have some questions, I am wondering if you can share upstream thought w.r.t the future development of intel_idle. > > - It looks to me since v5.6 intel_idle will prefer _CST of ACPI rather than the general table embedded in this driver.
Not exactly.
The rules are as follows: * If there is a built-in table for the given processor in the driver, it will be used, but the C-states that are not exposed in _CST will be disabled by default (the state parameters come from the built-in table for all C-states). * Otherwise (i.e. the driver does not recognized the given processor), C-state definitions will be based on the _CST data.
See https://www.kernel.org/doc/html/latest/admin-guide/pm/intel_idle.html for details.
> - Any pros and cons of using the tables of _CST in firmware and embedded one in the kernel?
Both can be used at the same time (see above).
The built-in table in the kernel must be suitable for all of the platforms shipped with the given processor (SoC).
Obviously, the _CST table allows intel_idle to work if the processor included in the platform is not recognized by it.
Generally, our planned strategy is to provide built-in C-state tables for all new "mainstream" processors with the use_acpi flag set to avoid enabling C-states that may have not been validated on a given platform by default.
> - Can the table in _CST archive more optimal idle states management?
Possibly, but not likely.
> If there is already any reference, documents I missed, kindly enlighten me then I would like to read it first before refining the questions.
See above. :-)
Thanks!
___________________________________ > 從: Rafael J. Wysocki [rafael@kernel.org] > 寄件日期: 2020年3月5日 上午 05:14 > 至: Pan, Harry > 副本: Rafael J. Wysocki; LKML; Harry Pan; Jacob Pan; Len Brown; Linux PM > 主旨: Re: [PATCH v3] intel_idle: Add Comet Lake support > > On Wed, Mar 4, 2020 at 12:57 PM Pan, Harry <harry.pan@intel.com> wrote: > > > > Hi Rafael, > > > > Yes, I skipped it considering to align CML-U V0 and A0 stepping w/ the same table; I sent v4 for your review. > > Skipping that flag is risky, because it may cause some C-states to be > enabled on systems where they have not been validated (e.g. systems > shipping with other OSes which only use _CST C-states). There were > problems related to that in the past which is one of the reasons for > adding _CST support to intel_idle. use_acpi should be set for all new > platforms going forward as a rule. > > > In the other hand, I am proposing using _CST as long term plan in CrOS dev teams. > > That I obviously agree with. :-) > > > > > On Mar 4, 2020, at 17:53, Rafael J. Wysocki <rafael@kernel.org> wrote: > > > > > > On Tue, Mar 3, 2020 at 10:10 AM Harry Pan <harry.pan@intel.com> wrote: > > >> > > >> Add a general C-state table in order to support Comet Lake. > > >> > > >> Signed-off-by: Harry Pan <harry.pan@intel.com> > > >> > > >> --- > > >> > > >> drivers/idle/intel_idle.c | 7 +++++++ > > >> 1 file changed, 7 insertions(+) > > >> > > >> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c > > >> index d55606608ac8..05bce595fafe 100644 > > >> --- a/drivers/idle/intel_idle.c > > >> +++ b/drivers/idle/intel_idle.c > > >> @@ -1067,6 +1067,11 @@ static const struct idle_cpu idle_cpu_dnv = { > > >> .use_acpi = true, > > >> }; > > >> > > >> +static const struct idle_cpu idle_cpu_cml = { > > >> + .state_table = skl_cstates, > > >> + .disable_promotion_to_c1e = true, > > > > > > .use_acpi = true, > > > > > > missing? Otherwise you can just use idle_cpu_skl as is, can't you? > > > > > >> +}; > > >> + > > >> static const struct x86_cpu_id intel_idle_ids[] __initconst = { > > >> INTEL_CPU_FAM6(NEHALEM_EP, idle_cpu_nhx), > > >> INTEL_CPU_FAM6(NEHALEM, idle_cpu_nehalem), > > >> @@ -1105,6 +1110,8 @@ static const struct x86_cpu_id intel_idle_ids[] __initconst = { > > >> INTEL_CPU_FAM6(ATOM_GOLDMONT_PLUS, idle_cpu_bxt), > > >> INTEL_CPU_FAM6(ATOM_GOLDMONT_D, idle_cpu_dnv), > > >> INTEL_CPU_FAM6(ATOM_TREMONT_D, idle_cpu_dnv), > > >> + INTEL_CPU_FAM6(COMETLAKE_L, idle_cpu_cml), > > >> + INTEL_CPU_FAM6(COMETLAKE, idle_cpu_cml), > > >> {} > > >> }; > > >> > > >> -- > > >> 2.24.1 > > >>
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