From: Stephen Boyd <sboyd@kernel.org>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>,
<u.kleine-koenig@pengutronix.de>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>,
Claudiu Beznea <claudiu.beznea@microchip.com>,
Michael Turquette <mturquette@baylibre.com>,
linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] clk: at91: avoid sleeping early
Date: Tue, 24 Sep 2019 13:20:15 -0700 [thread overview]
Message-ID: <20190924202015.EFEBF20640@mail.kernel.org> (raw)
In-Reply-To: <20190924122147.fojcu5u44letrele@pengutronix.de>
Quoting Uwe (2019-09-24 05:21:47)
> On Fri, Sep 20, 2019 at 05:39:06PM +0200, Alexandre Belloni wrote:
> > Note that this was already discussed a while ago and Arnd said this approach was
> > reasonable:
> > https://lore.kernel.org/lkml/6120818.MyeJZ74hYa@wuerfel/
> >
> > drivers/clk/at91/clk-main.c | 5 ++++-
> > drivers/clk/at91/sckc.c | 20 ++++++++++++++++----
> > 2 files changed, 20 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/clk/at91/clk-main.c b/drivers/clk/at91/clk-main.c
> > index f607ee702c83..ccd48e7a3d74 100644
> > --- a/drivers/clk/at91/clk-main.c
> > +++ b/drivers/clk/at91/clk-main.c
> > @@ -293,7 +293,10 @@ static int clk_main_probe_frequency(struct regmap *regmap)
> > regmap_read(regmap, AT91_CKGR_MCFR, &mcfr);
> > if (mcfr & AT91_PMC_MAINRDY)
> > return 0;
> > - usleep_range(MAINF_LOOP_MIN_WAIT, MAINF_LOOP_MAX_WAIT);
> > + if (system_state < SYSTEM_RUNNING)
> > + udelay(MAINF_LOOP_MIN_WAIT);
> > + else
> > + usleep_range(MAINF_LOOP_MIN_WAIT, MAINF_LOOP_MAX_WAIT);
>
> Given that this construct is introduced several times, I wonder if we
> want something like:
>
> static inline void early_usleep_range(unsigned long min, unsigned long max)
> {
> if (system_state < SYSTEM_RUNNING)
> udelay(min);
> else
> usleep_range(min, max);
> }
>
Maybe, but I think the intent is to not encourage this behavior? So
providing a wrapper will make it "easy" and then we'll have to tell
users to stop calling it. Another idea would be to make usleep_range()
"do the right thing" and call udelay if the system isn't running. And
another idea from tlgx[1] is to pull the delay logic into another clk op
that we can call to see when the enable or prepare is done. That may be
possible by introducing another clk_ops callback that when present
indicates we should sleep or delay for so much time while waiting for
the prepare or enable to complete.
[1] https://lkml.kernel.org/r/alpine.DEB.2.11.1606061448010.28031@nanos
next prev parent reply other threads:[~2019-09-24 20:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-20 15:39 [PATCH] clk: at91: avoid sleeping early Alexandre Belloni
[not found] ` <20190923165848.3108A20882@mail.kernel.org>
2019-09-23 21:34 ` Alexandre Belloni
2019-09-24 12:21 ` Uwe Kleine-König
2019-09-24 20:20 ` Stephen Boyd [this message]
2019-10-05 20:05 ` Alexandre Belloni
2019-10-28 14:54 ` Stephen Boyd
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=20190924202015.EFEBF20640@mail.kernel.org \
--to=sboyd@kernel.org \
--cc=alexandre.belloni@bootlin.com \
--cc=claudiu.beznea@microchip.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-clk@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mturquette@baylibre.com \
--cc=nicolas.ferre@microchip.com \
--cc=u.kleine-koenig@pengutronix.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).