netdev - Re: [PATCH] net/irda: add clk_prepare/clk_unprepare to pxaficp

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Date:	Sat, 17 Mar 2012 11:43:09 +0100
From:	Philipp Zabel <philipp.zabel@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, eric.y.miao@...il.com,
	haojian.zhuang@...vell.com, samuel@...tiz.org
Subject: Re: [PATCH] net/irda: add clk_prepare/clk_unprepare to pxaficp_ir

On Sat, Mar 17, 2012 at 7:10 AM, David Miller <davem@...emloft.net> wrote:
> From: Philipp Zabel <philipp.zabel@...il.com>
> Date: Thu, 15 Mar 2012 19:19:29 +0100
>
>> This patch adds clk_prepare/clk_unprepare calls to the pxaficp_ir
>> driver by using the helper functions clk_prepare_enable and
>> clk_disable_unprepare.
>>
>> Signed-off-by: Philipp Zabel <philipp.zabel@...il.com>
>
> This is terrible.
>
> So the problem was that clk_enable can't be invoked from atomic
> context, because it wants to take a mutex for some implementation.
>
> Therefore an existing routine with well defined semantics,
> clk_enable(), was turned into a NOP.
>
> And this silently breaks drivers.
>
> Instead of silently breaking things, make direct
> clk_enable()/clk_disable() invocations either result in a compile
> error or a run-time BUG_ON().

I expect that anybody who turns clk_enable/clk_disable into
no-ops for their platform will be sensible enough to take care of this.
The common struct clk framework already keeps a prepare_count
variable and clk_enable does WARN_ON(clk->prepare_count == 0).

In case of PXA, it's the clk_prepare/clk_unprepare calls that are the
no-ops anyway, so thanks for applying.

regards
Philipp
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