From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Michael Turquette <mturquette@baylibre.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-clk <linux-clk@vger.kernel.org>,
Stephen Boyd <sboyd@codeaurora.org>,
Lee Jones <lee.jones@linaro.org>,
Maxime Ripard <maxime.ripard@free-electrons.com>,
Sascha Hauer <s.hauer@pengutronix.de>,
Sekhar Nori <nsekhar@ti.com>, Kevin Hilman <khilman@kernel.org>,
Santosh Shilimkar <ssantosh@kernel.org>,
Tony Lindgren <tony@atomide.com>,
"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Linux-sh list <linux-sh@vger.kernel.org>,
Linux PM list <linux-pm@vger.kernel.org>
Subject: Re: [PATCH RFC RFT 2/3] clk: clk_put WARNs if user has not disabled clk
Date: Wed, 21 Oct 2015 18:46:35 +0200 [thread overview]
Message-ID: <CAMuHMdWgf8DOhaDLcQ=qJx0r7G0zK_yfWRpVOPBV--SW2Rw1kA@mail.gmail.com> (raw)
In-Reply-To: <20151021155057.20687.14055@quantum>
Hi Mike,
On Wed, Oct 21, 2015 at 5:50 PM, Michael Turquette
<mturquette@baylibre.com> wrote:
> Quoting Russell King - ARM Linux (2015-10-21 03:59:32)
>> On Wed, Oct 21, 2015 at 11:50:07AM +0200, Geert Uytterhoeven wrote:
>> > On Tue, Oct 20, 2015 at 2:40 PM, Michael Turquette
>> > <mturquette@baylibre.com> wrote:
>> > > Why not keep the reference to the struct clk after get'ing it the first
>> > > time?
>> >
>> > And store it where?
>>
>> Not my problem :)
>>
>> Users are supposed to hold on to the reference obtained via clk_get()
>> while they're making use of the clock: in some implementations, this
>> increments the module use count if the clock driver is a module, and
>> may have other effects too.
>>
>> Dropping that while you're still requiring the clock to be enabled is
>> unsafe: if it is provided by a module, then removing and reinserting
>> the module may very well change the enabled state of the clock, it
>> most certainly will disrupt the enable count.
>>
>> It's always been this way, right from the outset, and when I've seen
>> people doing this bollocks, I've always pointed out that it's wrong.
>> Generally, people will fix it once they become aware of it, so it's
>> really that people just don't like reading and conforming to published
>> API requirements.
>>
>> I think the root cause is that people just don't like reading what
>> other people write in terms of documentation, and they prefer to go
>> off and do their own thing, provided it works for them.
>
> Right, so in other words this problem must be solved by the caller of
> clk_get, as it should be. I have never much looked at the pm clk code in
> question, but I gave it a quick look and came up with some example code
> that does not compile, in an effort to be as helpful as possible.
>
> Basically I added a flex array to struct pm_clk_notifier_block, so that
> now there are two flex arrays which is stupid. But I am too lazy to
> replace the nbclk->clks thing with a malloc after walking all of the
> clk_id's to figure out the number of clocks. Or we could just add
> .num_clk to the struct, fix up all 4 users of it and drop the NULL
> sentinel used the .clk_id's... Hmm that would have been better.
Thanks for trying.
> index 25266c6..45e58fe 100644
> --- a/include/linux/pm_clock.h
> +++ b/include/linux/pm_clock.h
> @@ -16,6 +16,7 @@ struct pm_clk_notifier_block {
> struct notifier_block nb;
> struct dev_pm_domain *pm_domain;
> char *con_ids[];
> + struct clk *clks[];
> };
>
> struct clk;
Unfortunately that won't work: while the .con_ids[] array is per-platform,
the .clks[] array should be per-device. I.e. it should be tied to the struct
device, not to the struct pm_clk_notifier_block.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2015-10-21 16:46 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-07 19:09 [PATCH RFC RFT 0/3] clk: detect per-user enable imbalances and implement hand-off Michael Turquette
2015-08-07 19:09 ` [PATCH RFC RFT 1/3] clk: per-user clk prepare & enable ref counts Michael Turquette
2015-08-10 13:47 ` Maxime Coquelin
2015-08-10 19:31 ` Michael Turquette
2015-08-07 19:09 ` [PATCH RFC RFT 2/3] clk: clk_put WARNs if user has not disabled clk Michael Turquette
2015-09-30 15:38 ` Geert Uytterhoeven
[not found] ` <20151020124000.20687.60752@quantum>
2015-10-20 12:52 ` Russell King - ARM Linux
2015-10-21 9:50 ` Geert Uytterhoeven
2015-10-21 10:59 ` Russell King - ARM Linux
2015-10-21 15:50 ` Michael Turquette
2015-10-21 16:46 ` Geert Uytterhoeven [this message]
2015-08-07 19:09 ` [PATCH RFC RFT 3/3] clk: introduce CLK_ENABLE_HAND_OFF flag Michael Turquette
2015-08-10 14:48 ` Lee Jones
[not found] ` <20150810185516.2416.32293@quantum>
2015-08-11 8:43 ` Lee Jones
2015-08-11 10:02 ` Maxime Coquelin
2015-08-11 10:11 ` Geert Uytterhoeven
2015-08-11 11:36 ` Maxime Coquelin
2015-08-11 11:41 ` Maxime Coquelin
2015-08-11 11:49 ` Geert Uytterhoeven
2015-08-11 12:03 ` Maxime Coquelin
2015-08-11 12:34 ` Geert Uytterhoeven
2015-08-11 12:03 ` Lee Jones
2015-08-11 17:09 ` Michael Turquette
2015-08-11 18:17 ` Lee Jones
2015-08-12 7:27 ` Geert Uytterhoeven
2015-08-12 7:51 ` Lee Jones
2015-08-11 17:09 ` Michael Turquette
2015-08-11 18:20 ` Lee Jones
[not found] ` <20150811170904.2416.43354@quantum>
2015-08-11 18:33 ` Lee Jones
[not found] ` <20150811185827.31346.68194@quantum>
2015-08-18 15:52 ` Maxime Ripard
[not found] ` <20150818163356.31346.15075@quantum>
2015-08-20 15:11 ` Maxime Ripard
2015-08-18 15:58 ` Maxime Ripard
[not found] ` <20150818163931.31346.78267@quantum>
2015-08-20 15:39 ` Maxime Ripard
2015-08-10 15:36 ` [PATCH RFC RFT 0/3] clk: detect per-user enable imbalances and implement hand-off Lee Jones
[not found] ` <20150810192810.2416.25672@quantum>
2015-08-11 9:11 ` Lee Jones
2015-08-11 9:20 ` Geert Uytterhoeven
[not found] ` <20150811164151.2416.33353@quantum>
2015-08-11 17:42 ` Geert Uytterhoeven
2015-08-18 15:45 ` Maxime Ripard
[not found] ` <20150818164356.31346.80341@quantum>
2015-08-20 15:15 ` Maxime Ripard
[not found] ` <20150825215051.31346.56261@quantum>
2015-08-26 6:54 ` Lee Jones
2015-08-26 8:42 ` Maxime Coquelin
2015-08-26 9:09 ` Lee Jones
2015-08-26 9:37 ` Maxime Coquelin
2015-08-26 20:41 ` Lee Jones
2015-08-29 3:49 ` Maxime Ripard
2015-08-29 3:55 ` Maxime Ripard
[not found] ` <20150930123649.3201.75689@quantum>
2015-10-01 19:56 ` Maxime Ripard
2015-11-24 9:48 ` Heiko Stübner
2015-12-05 0:46 ` Michael Turquette
2016-02-11 21:33 ` Michael Turquette
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