linux-kernel - RE: [PATCH v3 3/8] cpufreq: amd-pstate: change driver to be built-in type

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Message-ID: <DM4PR12MB52781ED15FCD6409D4EA6AFD9C029@DM4PR12MB5278.namprd12.prod.outlook.com>
Date:   Sun, 13 Nov 2022 16:21:36 +0000
From:   "Yuan, Perry" <Perry.Yuan@....com>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>,
        "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "Huang, Ray" <Ray.Huang@....com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "Karny, Wyes" <Wyes.Karny@....com>
CC:     "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Huang, Shimmer" <Shimmer.Huang@....com>,
        "Du, Xiaojian" <Xiaojian.Du@....com>,
        "Meng, Li (Jassmine)" <Li.Meng@....com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 3/8] cpufreq: amd-pstate: change driver to be built-in
 type

[AMD Official Use Only - General]



> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@....com>
> Sent: Tuesday, November 8, 2022 2:30 AM
> To: Yuan, Perry <Perry.Yuan@....com>; rafael.j.wysocki@...el.com; Huang,
> Ray <Ray.Huang@....com>; viresh.kumar@...aro.org; Karny, Wyes
> <Wyes.Karny@....com>
> Cc: Sharma, Deepak <Deepak.Sharma@....com>; Fontenot, Nathan
> <Nathan.Fontenot@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Huang, Shimmer
> <Shimmer.Huang@....com>; Du, Xiaojian <Xiaojian.Du@....com>; Meng,
> Li (Jassmine) <Li.Meng@....com>; linux-pm@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH v3 3/8] cpufreq: amd-pstate: change driver to be built-in
> type
> 
> + wyes.karny@....com
> 
> You should sync with Wyes Karny on this patch, I think he had some different
> ideas that you guys should fold together for v4 of this series.  I'll leave some
> direct comments on your implementation below.
> 
> Also, include him in on CC for your v4.
> 
> On 11/7/2022 11:57, Perry Yuan wrote:
> > Change the `amd-pstate` driver as the built-in type which can help to
> > load the driver before the acpi_cpufreq driver as the default pstate
> > driver for the AMD processors.
> >
> > for the processors do not have the dedicated MSR functions, add
> > `amd-pstate=legacy_cppc` to grub which enable shared memmory interface
> > to communicate with cppc_acpi module to control pstate hints.
> 
> 1) s/memmory/memory/
> 2) Although many users will use GRUB to configure their kernel command
> line you should not assume it in the commit message.

Fixed in V4. 

> 
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> > ---
> >   drivers/cpufreq/amd-pstate.c | 23 +++++++++++++----------
> >   1 file changed, 13 insertions(+), 10 deletions(-)
> 
> You need to document the new early parameter support in kernel-
> parameters.txt, and should also put it in amd-pstate.rst.
> 
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index ace7d50cf2ac..14906431dc15
> 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -59,10 +59,7 @@
> >    * we disable it by default to go acpi-cpufreq on these processors and add
> a
> >    * module parameter to be able to enable it manually for debugging.
> >    */
> > -static bool shared_mem = false;
> > -module_param(shared_mem, bool, 0444); -
> MODULE_PARM_DESC(shared_mem,
> > -		 "enable amd-pstate on processors with shared memory
> solution (false = disabled (default), true = enabled)");
> > +static bool shared_mem __read_mostly;
> >
> >   static struct cpufreq_driver amd_pstate_driver;
> >
> > @@ -653,16 +650,22 @@ static int __init amd_pstate_init(void)
> >
> >   	return ret;
> >   }
> > +device_initcall(amd_pstate_init);
> >
> > -static void __exit amd_pstate_exit(void)
> > +static int __init amd_pstate_param(char *str)
> >   {
> > -	cpufreq_unregister_driver(&amd_pstate_driver);
> > +	if (!str)
> > +		return -EINVAL;
> >
> > -	amd_pstate_enable(false);
> > -}
> > +	/* enable shared memory type CPPC ,if you processor has no MSR,
> you have to add this
> > +	 * to your grub to make cppc driver loaded successfully.
> 
> Don't reference GRUB here, it should be referenced from the kernel
> command line.
> 
> > +	 */
> > +	if (!strcmp(str, "legacy_cppc"))
> > +		shared_mem = true;
> Sync with Wyes about this.  He had some different strings and flow in mind
> which I think would be more preferable.

Aligned with Wyes, 
Some new changes brought  into V4.
Please help to take a look at the new patch.
Thanks

Perry. 


> 
> >
> > -module_init(amd_pstate_init);
> > -module_exit(amd_pstate_exit);
> > +	return 0;
> > +}
> > +early_param("amd-pstate", amd_pstate_param);
> >
> >   MODULE_AUTHOR("Huang Rui <ray.huang@....com>");
> >   MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");