From: "Sanil, Shruthi" <shruthi.sanil@intel.com>
To: Daniel Lezcano <daniel.lezcano@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
"robh+dt@kernel.org" <robh+dt@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>
Cc: "andriy.shevchenko@linux.intel.com"
<andriy.shevchenko@linux.intel.com>,
"kris.pan@linux.intel.com" <kris.pan@linux.intel.com>,
"mgross@linux.intel.com" <mgross@linux.intel.com>,
"Thokala, Srikanth" <srikanth.thokala@intel.com>,
"Raja Subramanian,
Lakshmi Bai" <lakshmi.bai.raja.subramanian@intel.com>,
"Sangannavar,
Mallikarjunappa" <mallikarjunappa.sangannavar@intel.com>
Subject: RE: [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer support
Date: Fri, 24 Dec 2021 09:40:53 +0000 [thread overview]
Message-ID: <BN9PR11MB554543CAACA5FD468B6692F9F17F9@BN9PR11MB5545.namprd11.prod.outlook.com> (raw)
In-Reply-To: <f8af5711-4cc4-7513-5ad3-0f17ce04b346@linaro.org>
> -----Original Message-----
> From: Daniel Lezcano <daniel.lezcano@linaro.org>
> Sent: Thursday, December 23, 2021 7:46 PM
> To: Sanil, Shruthi <shruthi.sanil@intel.com>; Thomas Gleixner
> <tglx@linutronix.de>; robh+dt@kernel.org; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org
> Cc: andriy.shevchenko@linux.intel.com; kris.pan@linux.intel.com;
> mgross@linux.intel.com; Thokala, Srikanth <srikanth.thokala@intel.com>;
> Raja Subramanian, Lakshmi Bai <lakshmi.bai.raja.subramanian@intel.com>;
> Sangannavar, Mallikarjunappa <mallikarjunappa.sangannavar@intel.com>
> Subject: Re: [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer support
>
> On 11/11/2021 11:42, Sanil, Shruthi wrote:
> >> -----Original Message-----
> >> From: Thomas Gleixner <tglx@linutronix.de>
> >> Sent: Monday, September 27, 2021 3:11 AM
> >> To: Sanil, Shruthi <shruthi.sanil@intel.com>;
> >> daniel.lezcano@linaro.org;
> >> robh+dt@kernel.org; linux-kernel@vger.kernel.org;
> >> devicetree@vger.kernel.org
> >> Cc: andriy.shevchenko@linux.intel.com; kris.pan@linux.intel.com;
> >> mgross@linux.intel.com; Thokala, Srikanth
> >> <srikanth.thokala@intel.com>; Raja Subramanian, Lakshmi Bai
> >> <lakshmi.bai.raja.subramanian@intel.com>;
> >> Sangannavar, Mallikarjunappa
> <mallikarjunappa.sangannavar@intel.com>;
> >> Sanil, Shruthi <shruthi.sanil@intel.com>
> >> Subject: Re: [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer
> >> support
> >>
> >> On Tue, Sep 07 2021 at 00:06, shruthi sanil wrote:
> >>> +
> >>> +/* Provides a unique ID for each timer */ static
> >>> +DEFINE_IDA(keembay_timer_ida);
> >>
> >>> +
> >>> + timer_id = ida_alloc(&keembay_timer_ida, GFP_KERNEL);
> >>> + if (timer_id < 0) {
> >>> + ret = timer_id;
> >>> + goto err_keembay_ce_to_free;
> >>> + }
> >>
> >> May I ask what the purpose of the IDA, which is backed by a full
> >> blown xarray, is here?
> >>
> >> AFAICT all you want is a unique number for the timer name for up to 8
> >> timers.
> >>
> >>> + timer_name = kasprintf(GFP_KERNEL, "keembay_timer%d",
> >> timer_id);
> >>
> >> So what's wrong about:
> >>
> >> static unsigned int keembay_timer_id;
> >>
> >> timer_name = kasprintf(GFP_KERNEL, "keembay_timer%d",
> >> keembay_timer_id++);
> >>
> >> Hmm?
> >
> > Yes, we had initially implemented it in the similar way, but in the
> > course of review it got changed to use IDA.
> >
> >>
> >>> +
> >>> + clockevents_config_and_register(&keembay_ce_to->clkevt,
> >>> + timer_of_rate(keembay_ce_to),
> >>> + 1,
> >>> + U32_MAX);
> >>
> >> Aside of that what's the point of registering more than one of those
> >> timers as clock event? The core will only use one and the rest is
> >> just going to use memory for no value.
> >
> > Instead of
> > keembay_ce_to->clkevt.cpumask = cpumask_of(0); can I update it as
> > keembay_ce_to->clkevt.cpumask = cpu_possible_mask; so that each timer
> > would be associated with different cores?
>
> Let me try to clarify:
>
> The Intel Keem bay Soc is a 4 x Cortex-A53
>
> The arch ARM timer is per CPU on this platform.
>
> Case 1:
> -------
> - the architected timer is not desired and this timer is wanted to be used
> instead (but rating tells the opposite) => rewrite per cpu code
>
> Case 2:
> -------
> - the architected timer are desired and this timer is used as a broadcast
> timer when a core is going done with cpuidle. One timer is needed.
>
> - In order to prevent useless wakeup, the timer uses the flag DYNIRQ.
> However, cpumask_of(0) is set and makes inoperative this flag. In order to
> make full use of it, clkevt.cpumask must be cpu_possible_mask
>
> Hope that helps
>
> -- Daniel
>
Thank You Daniel for the explanation.
In case of KMB, we are using the ARM architecture timer.
We would be using the timer for case2. So I need to register Just 1 timer.
I'll check and make the changes accordingly and submit the next patch.
Thank You!
Regards,
Shruthi
>
>
>
>
>
>
>
> --
> <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
>
> Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
> <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-
> blog/> Blog
next prev parent reply other threads:[~2021-12-24 9:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-06 18:36 [PATCH v6 0/2] Add the driver for Intel Keem Bay SoC timer block shruthi.sanil
2021-09-06 18:36 ` [PATCH v6 1/2] dt-bindings: timer: Add bindings for Intel Keem Bay SoC Timer shruthi.sanil
2021-09-07 11:49 ` Rob Herring
2021-09-06 18:36 ` [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer support shruthi.sanil
2021-09-26 21:41 ` Thomas Gleixner
2021-11-11 10:42 ` Sanil, Shruthi
2021-12-23 14:16 ` Daniel Lezcano
2021-12-24 9:40 ` Sanil, Shruthi [this message]
2021-11-25 17:29 ` Sanil, Shruthi
2021-12-15 16:23 ` Sanil, Shruthi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=BN9PR11MB554543CAACA5FD468B6692F9F17F9@BN9PR11MB5545.namprd11.prod.outlook.com \
--to=shruthi.sanil@intel.com \
--cc=andriy.shevchenko@linux.intel.com \
--cc=daniel.lezcano@linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=kris.pan@linux.intel.com \
--cc=lakshmi.bai.raja.subramanian@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mallikarjunappa.sangannavar@intel.com \
--cc=mgross@linux.intel.com \
--cc=robh+dt@kernel.org \
--cc=srikanth.thokala@intel.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).