From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Stephen Boyd <sboyd@codeaurora.org>, Rob Herring <robh@kernel.org>
Cc: linux-clk <linux-clk@vger.kernel.org>,
Michael Turquette <mturquette@baylibre.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: of_clk_add_(hw_)providers multipule times for one node?
Date: Mon, 8 Aug 2016 01:54:23 +0900 [thread overview]
Message-ID: <CAK7LNAQfwh3Z_=VWHvDi6EXFtVLuRMFVYzKMq8qCaZ30jfCq8g@mail.gmail.com> (raw)
In-Reply-To: <20160804212553.GB15690@codeaurora.org>
Hi Stephen,
2016-08-05 6:25 GMT+09:00 Stephen Boyd <sboyd@codeaurora.org>:
> +Rob in case he has any insight
>
> On 07/09, Masahiro Yamada wrote:
>> Hi.
>>
>> I think the current code allows to add
>> clk_providers multiple times against one DT node.
>>
>> Are there cases that really need to do so?
>
> If we have clk drivers that have a device driver structure and
> also use CLK_OF_DECLARE then we could get into a situation where
> they register two providers for the same device node. I can't
> think of any other situation where this would happen though.
What is the benefit for splitting one clock device
into CLK_OF_DECLARE() and a platform_driver?
If we go this way, I think we need to fix the current code.
of_clk_add_provider() calls of_clk_del_provider()
in its failure path.
Notice of_clk_del_provider() unregister
all the providers associated with the device node.
So, if of_clk_add_provider() fails to register a platform driver,
it may unregister another provider added by OF_CLK_DECLARE().
Some platform drivers call of_clk_del_provider() in a .remove callback,
so the same problem could happen.
Why does of_clk_del_provider() take (struct device_node *np) ?
Shouldn't it take (struct of_clk_provider *cp)?
> It used to return the last provider's error, but I accidentally
> changed that behavior when adding clk_hw providers in commit
> 0861e5b8cf80 (clk: Add clk_hw OF clk providers, 2016-02-05).
> Nobody seems to have complained though, so you're the first to
> have reported this.
If we allow multiple OF-providers for one device node,
I think any error should be treated as EPROBE_DEFER,
i.e. the current code is good.
The scenario is:
- Clocks with ID 0 thru 3 are provided by CLK_OF_DECLARE()
- Clocks with ID 4 thru 9 are provided by a platform driver.
What if a clock consumer requests the clk ID 5
after CLK_OF_DECLARE(), but before the clk platform driver is registered?
If the clock consumer gets the last provider's error
(-EINVAL returned from CLK_OR_DECLARE one in this case)
it will lose a chance to retry it after clocks from a platform driver
are registered.
A bit nasty...
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2016-08-07 16:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-08 17:23 of_clk_add_(hw_)providers multipule times for one node? Masahiro Yamada
2016-08-04 21:25 ` Stephen Boyd
2016-08-04 22:02 ` Rob Herring
2016-08-07 16:54 ` Masahiro Yamada [this message]
2016-08-08 9:00 ` Geert Uytterhoeven
2016-08-08 23:37 ` Stephen Boyd
2016-08-10 7:59 ` Masahiro Yamada
2016-08-10 23:08 ` Stephen Boyd
2016-08-12 7:04 ` Masahiro Yamada
2016-08-24 7:11 ` Masahiro Yamada
2016-08-24 18:08 ` Stephen Boyd
2016-08-25 2:36 ` Masahiro Yamada
2016-08-25 20:30 ` Stephen Boyd
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