linux-kernel - Re: [RFC PATCH v3 1/2] clk: samsung: Add a clock lookup function

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Date:	Tue, 31 Mar 2015 01:02:29 +0900
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	Mike Turquette <mturquette@...aro.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Kukjin Kim <kgene@...nel.org>, Olof Johansson <olof@...om.net>,
	Doug Anderson <dianders@...omium.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Kevin Hilman <khilman@...aro.org>,
	Tyler Baker <tyler.baker@...aro.org>,
	Abhilash Kesavan <kesavan.abhilash@...il.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 1/2] clk: samsung: Add a clock lookup function

Hi Javier,

2015-03-31 0:53 GMT+09:00 Javier Martinez Canillas
<javier.martinez@...labora.co.uk>:
> The Samsung helpers functions to register clocks, add the clock instance
> returned by the common clock framework to a lookup table that is used by
> OF to lookup the clocks.
>
> But this table could also be useful to clock drivers if they need to get
> a clock instance since the helper functions don't return them.
>
> The common clock framework __clk_lookup() function from the clk provider
> API could be used by drivers as well. But it's more efficient to use the
> Samsung specific lookup table that returns the clock instance in constant
> time, than using the __clk_lookup() function that uses the clock name as
> an index so it has a linear search time.

Is this really something we should be concerned about? If so, maybe
the generic look-up function should be rewritten to use something
faster, such as tree or hash table?

Best regards,
Tomasz
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