Re: [RFC, PATCH 3/3] clk: add warnings for incorrect enable/prepare

On 02/07/2011 06:24 AM, Nicolas Pitre wrote:

On Mon, 7 Feb 2011, Jeremy Kerr wrote:

quoted

Hi Uwe,

quoted

This implies the warning is only issued on clocks that have a prepare
callback.  If we want to enforce the new API the warning here shouldn't
depend on clk->ops->prepare.  (clk_prepare and clk_unprepare need to
be changed then to adapt the prepare_count even in the absence of
clk->ops->prepare.)

Yeah, it's a decision about either adding a small cost to all clk_prepare()s
(ie, adding cost when there is no prepare callback), or checking for the
correct prepare/enable semantics for all clocks (even when it doesn't matter
for that particular clock). I chose the first as more important, but happy to
go either way here.

The prepare method being called from non-atomic context cannot be
considered to be in a speed critical path.  Most of the time, this is
going to be called on driver initialization or the like, and that's a
relatively rare event. Therefore this really small cost to clk_prepare()
is definitively worth it to help proper usage of the API.  If this ever
becomes a problem then this could be confined to some CONFIG_CLK_DEBUG
or the like.  But when introducing a new API it is best to be more
strict to help people get its usage right (without going overboard with
it of course).

Agree with Nicholas and Uwe. +1 for this request.

-Saravana

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