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Message-ID: <1981330.kGUrTurMy5@diego>
Date: Fri, 01 May 2015 21:59:55 +0200
From: Heiko Stübner <heiko@...ech.de>
To: Stephen Boyd <sboyd@...eaurora.org>
Cc: mturquette@...aro.org, dianders@...omium.org,
linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Boris Brezillon <boris.brezillon@...e-electrons.com>,
Alex Elder <elder@...aro.org>,
Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
Stephen Warren <swarren@...dotorg.org>,
Max Filippov <jcmvbkbc@...il.com>, kernel@...gutronix.de,
Zhangfei Gao <zhangfei.gao@...aro.org>,
Santosh Shilimkar <ssantosh@...nel.org>,
Chao Xie <chao.xie@...vell.com>,
Jason Cooper <jason@...edaemon.net>,
Stefan Wahren <stefan.wahren@...e.com>,
Andrew Bresticker <abrestic@...omium.org>,
Robert Jarzmik <robert.jarzmik@...e.fr>,
Georgi Djakov <georgi.djakov@...aro.org>,
Sylwester Nawrocki <s.nawrocki@...sung.com>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Barry Song <baohua@...nel.org>,
Dinh Nguyen <dinguyen@...nsource.altera.com>,
Viresh Kumar <viresh.linux@...il.com>,
Gabriel FERNANDEZ <gabriel.fernandez@...com>,
emilio@...pez.com.ar, Peter De Schrijver <pdeschrijver@...dia.com>,
Tero Kristo <t-kristo@...com>,
Ulf Hansson <ulf.hansson@...aro.org>,
Pawel Moll <pawel.moll@....com>,
Michal Simek <michal.simek@...inx.com>
Subject: Re: [PATCH v3 0/2] clk: improve handling of orphan clocks
Am Donnerstag, 30. April 2015, 17:19:01 schrieb Stephen Boyd:
> On 04/22, Heiko Stuebner wrote:
> > Using orphan clocks can introduce strange behaviour as they don't have
> > rate information at all and also of course don't track
> >
> > This v2/v3 takes into account suggestions from Stephen Boyd to not try to
> > walk the clock tree at runtime but instead keep track of orphan states
> > on clock tree changes and making it mandatory for everybody from the
> > start as orphaned clocks should not be used at all.
> >
> >
> > This fixes an issue on most rk3288 platforms, where some soc-clocks
> > are supplied by a 32khz clock from an external i2c-chip which often
> > is only probed later in the boot process and maybe even after the
> > drivers using these soc-clocks like the tsadc temperature sensor.
> > In this case the driver using the clock should of course defer probing
> > until the clock is actually usable.
> >
> >
> > As this changes the behaviour for orphan clocks, it would of course
> > benefit from more testing than on my Rockchip boards. To keep the
> > recipent-list reasonable and not spam to much I selected one (the topmost)
> > from the get_maintainer output of each drivers/clk entry.
> > Hopefully some will provide Tested-by-tags :-)
>
> <grumble> I don't see any Tested-by: tags yet </grumble>. I've
> put these two patches on a separate branch "defer-orphans" and
> pushed it to clk-next so we can give it some more exposure.
>
> Unfortunately this doesn't solve the orphan problem for non-OF
> providers. What if we did the orphan check in __clk_create_clk()
> instead and returned an error pointer for orphans? I suspect that
> will solve all cases, right?
hmm, clk_register also uses __clk_create_clk, which in turn would prevent
registering orphan-clocks at all, I'd think.
As on my platform I'm dependant on orphan clocks (the soc-level clock gets
registerted as part of the big clock controller way before the i2c-based
supplying clock), I'd rather not touch this :-) .
Instead I guess we could hook it less deep into clk_get_sys, like in the
following patch?
------------ 8< ------------------------- >8 -----------------
From: Heiko Stuebner <heiko@...ech.de>
Date: Fri, 1 May 2015 21:50:46 +0200
Subject: [PATCH] clk: prevent orphan access on non-devicetree platforms too
The orphan-check in __of_clk_get_from_provider only prevents orphan-access
on devicetree platforms. To bring non-dt platforms to the same level of
functionality let clk_get_sys (called from clk_get for non-dt platforms)
also check for orphans and return -EPROBE_DEFER in that case.
Signed-off-by: Heiko Stuebner <heiko@...ech.de>
---
drivers/clk/clk.c | 2 +-
drivers/clk/clk.h | 5 +++++
drivers/clk/clkdev.c | 5 +++++
3 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 36d1a01..167d0bf 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2220,7 +2220,7 @@ static inline void clk_debug_unregister(struct clk_core *core)
}
#endif
-static bool clk_is_orphan(const struct clk *clk)
+bool clk_is_orphan(const struct clk *clk)
{
if (!clk)
return false;
diff --git a/drivers/clk/clk.h b/drivers/clk/clk.h
index 00b35a1..b8a6061 100644
--- a/drivers/clk/clk.h
+++ b/drivers/clk/clk.h
@@ -20,6 +20,7 @@ struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec,
struct clk *__clk_create_clk(struct clk_hw *hw, const char *dev_id,
const char *con_id);
void __clk_free_clk(struct clk *clk);
+bool clk_is_orphan(const struct clk *clk);
#else
/* All these casts to avoid ifdefs in clkdev... */
static inline struct clk *
@@ -32,5 +33,9 @@ static struct clk_hw *__clk_get_hw(struct clk *clk)
{
return (struct clk_hw *)clk;
}
+static inline bool clk_is_orphan(const struct clk *clk)
+{
+ return false;
+}
#endif
diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
index 1fcb6ef..ad96775 100644
--- a/drivers/clk/clkdev.c
+++ b/drivers/clk/clkdev.c
@@ -177,6 +177,11 @@ struct clk *clk_get_sys(const char *dev_id, const char *con_id)
if (!cl)
goto out;
+ if (clk_is_orphan(cl->clk)) {
+ clk = ERR_PTR(-EPROBE_DEFER);
+ goto out;
+ }
+
clk = __clk_create_clk(__clk_get_hw(cl->clk), dev_id, con_id);
if (IS_ERR(clk))
goto out;
--
2.1.4
--
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