From: Mike Turquette <mturquette@linaro.org>
To: Viresh Kumar <viresh.kumar@linaro.org>,
"Sascha Hauer" <s.hauer@pengutronix.de>
Cc: "Pi-Cheng Chen" <pi-cheng.chen@linaro.org>,
"Stephen Boyd" <sboyd@codeaurora.org>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
"Rob Herring" <robh+dt@kernel.org>,
"Pawel Moll" <pawel.moll@arm.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"Ian Campbell" <ijc+devicetree@hellion.org.uk>,
"Kumar Gala" <galak@codeaurora.org>,
"Henry Chen" <henryc.chen@mediatek.com>,
"James Liao" <jamesjj.liao@mediatek.com>,
"Chen Fan" <fan.chen@mediatek.com>,
"Eddie Huang" <eddie.huang@mediatek.com>,
"Joe.C" <yingjoe.chen@mediatek.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"Linaro Kernel Mailman List" <linaro-kernel@lists.linaro.org>,
linux-mediatek@lists.infradead.org
Subject: Re: [PATCH] clk: mediatek: Export CPU mux clocks for CPU frequency control
Date: Tue, 10 Mar 2015 16:59:12 -0700 [thread overview]
Message-ID: <20150310235912.14952.99786@quantum> (raw)
In-Reply-To: <CAKohponSqLPcULA9-T8y9b_b44Torti0p6W3sJfRZ1oKUWqtTw@mail.gmail.com>
Quoting Viresh Kumar (2015-03-05 00:59:50)
> On 5 March 2015 at 13:12, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> > We have clk_set_parent for changing the parent and clk_set_rate to
> > change the rate. Use the former for changing the parent and the latter
> > for changing the rate. What you are interested in is changing the
> > parent, so use clk_set_parent for this and not abuse a side effect
> > of clk_set_rate.
>
> clk_set_rate() for CPUs clock is responsible to change clock rate
> of the CPU. Whether it plays with PLLs or muxes, its not that relevant.
Agreed.
>
> > My suggestion is to take another approach. Implement clk_set_rate for
> > these muxes and in the set_rate hook:
> >
> > - switch mux to intermediate PLL parent
> > - call clk_set_rate() for the real parent PLL
> > - switch mux back to real parent PLL
> >
> > This way the things happening behind the scenes are completely transparent
> > to the cpufreq driver and you can use cpufreq-dt as is without changes.
>
> CPUFreq wants to change to intermediate frequency by itself against
> some magic change behind the scene. The major requirement for that
> comes from the fact that we want to send PRE/POST freq notifiers on
> which loops-per-jiffie depends.
I assume you are saying that you want to update loops-per-jiffie while
at an intermediate frequency. Why? This operation should not take very
long.
Imagine a (hypothetical?) processor that changes frequency in many small
steps until it converges to the target rate. Would you want to update
lpj for every step?
Regards,
Mike
next prev parent reply other threads:[~2015-03-11 0:28 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-04 10:49 [PATCH] clk: mediatek: Export CPU mux clocks for CPU frequency control pi-cheng.chen
2015-03-04 11:21 ` Sascha Hauer
2015-03-05 2:43 ` Pi-Cheng Chen
2015-03-05 7:42 ` Sascha Hauer
2015-03-05 8:58 ` Pi-Cheng Chen
2015-03-05 8:59 ` Viresh Kumar
2015-03-05 9:19 ` Sascha Hauer
2015-03-05 9:39 ` Pi-Cheng Chen
2015-03-05 10:51 ` Sascha Hauer
2015-03-05 11:02 ` Viresh Kumar
2015-03-11 0:13 ` Mike Turquette
2015-03-12 9:21 ` Viresh Kumar
2015-03-12 10:36 ` Russell King - ARM Linux
2015-03-05 11:33 ` Pi-Cheng Chen
2015-03-05 10:23 ` Viresh Kumar
2015-03-05 10:59 ` Sascha Hauer
2015-03-10 23:59 ` Mike Turquette [this message]
2015-03-12 9:22 ` Viresh Kumar
2015-03-10 1:53 ` Pi-Cheng Chen
2015-03-10 7:55 ` Sascha Hauer
2015-03-11 7:00 ` Pi-Cheng Chen
2015-07-14 12:47 [PATCH v4] " Daniel Kurtz
2015-07-15 6:38 ` [PATCH] " Pi-Cheng Chen
2015-08-03 11:13 ` Pi-Cheng Chen
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=20150310235912.14952.99786@quantum \
--to=mturquette@linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=eddie.huang@mediatek.com \
--cc=fan.chen@mediatek.com \
--cc=galak@codeaurora.org \
--cc=henryc.chen@mediatek.com \
--cc=ijc+devicetree@hellion.org.uk \
--cc=jamesjj.liao@mediatek.com \
--cc=linaro-kernel@lists.linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=mark.rutland@arm.com \
--cc=matthias.bgg@gmail.com \
--cc=pawel.moll@arm.com \
--cc=pi-cheng.chen@linaro.org \
--cc=robh+dt@kernel.org \
--cc=s.hauer@pengutronix.de \
--cc=sboyd@codeaurora.org \
--cc=viresh.kumar@linaro.org \
--cc=yingjoe.chen@mediatek.com \
/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).