Message-ID: <20130809045349.5348.29829@quantum>
Date:	Thu, 08 Aug 2013 21:53:49 -0700
From:	Mike Turquette <mturquette@...aro.org>
To:	James Hogan <james.hogan@...tec.com>,
	<linux-arm-kernel@...ts.infradead.org>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	<linux-kernel@...r.kernel.org>,
	Saravana Kannan <skannan@...eaurora.org>,
	Doug Anderson <dianders@...omium.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	"James Hogan" <james.hogan@...tec.com>
Subject: Re: [PATCH v6 0/5] clk: implement remuxing during set_rate

Quoting James Hogan (2013-07-29 04:24:57)
> This patchset adds support for automatic selection of the best parent
> for a clock mux, i.e. the one which can provide the closest clock rate
> to that requested. It can be disabled by a new CLK_SET_RATE_NO_REPARENT
> flag (which is set for all uses of clk_register_mux().
> 
> This works by way of adding a new op, determine_rate, similar to
> round_rate but with an extra parameter to allow the clock driver to
> optionally select a different parent clock. This is used in
> clk_calc_new_rates to decide whether to initiate a set_parent operation.

Hi James,

I'm performing some testing on this series now. If I don't spot any
regressions than I'll take it into clk-next. Thanks a lot for the rework
you've done.

I think that work on re-muxing is not yet complete. There are still
unresolved issues about picking "best parents", and likely some other
loose ends. We can fix those up later.

Regards,
Mike

> 
> Changes in v6:
> 
> * Rebased on v3.11-rc1.
> * Added changes to samsung/clk-exynos-audss.c, zynq/clkc.c.
> 
> Changes in v5:
> 
> * Rebased on latest clk-next ("clk: tegra: Use common of_clk_init
>   function")
> * Updated clock hardware characteristics table in documentation.
> 
> Changes in v4:
> 
> * rebased on clk-next ("clk: sun5i: Add compatibles for Allwinner A13").
> * replace __clk_set_parent_no_recalc with __clk_set_parent.
> * never pass NULL to determine_rate's best_parent_clk parameter, and
>   slight refactor of __clk_round_rate to use local copy of clk->parent.
> * a few new comments around use of clk::new_child.
> * new patch (patch 2) split out of patch 3 to avoid having to declare
>   static __clk_set_parent() at the top of clk.c, and to ease readability
>   of patch 3.
> 
> Changes in v3:
> 
> * rebased on v3.10-rc1.
> * remove double underscore prefix from clk_get_parent_by_index()
> * store new_parent_index in struct clk too (calculated from
>   clk_fetch_parent_index, and passed through __clk_set_parent_no_recalc
>   to __clk_set_parent).
> * allow determine_rate to satisfy recalc_rate check in __clk_init.
> * rename/invert CLK_SET_RATE_REMUX to CLK_SET_RATE_NO_REPARENT and move
>   to patch 3.
> * patch 3: add CLK_SET_RATE_NO_REPARENT flag to all callers of
>   clk_register_mux. If you don't mind your clocks being reparented in
>   response to set_rate please let me know and I'll drop the relevant
>   portion of the patch.
> 
> Changes in v2:
> 
> I've moved the mux determine_rate implementation into a core helper, but
> I haven't pushed it fully into the core, as I think it just wouldn't
> work correctly for more complex clocks, e.g. if you (theoretically) had
> a combined mux and divide, you'd want to intercept the determine_rate
> and ask for a larger rate from the parent clocks, then return the
> divided rate. This should be possible by wrapping the mux determine_rate
> helper.
> 
> Patch 1 still exports the __clk_get_parent_by_index as it seems like it
> might be a useful thing for clock implementations to have access to if
> they ever wanted to do something more fancy with changing clock parents.
> 
> I haven't made any attempt to implement the atomic set_parent+set_rate
> as I don't have hardware that could take proper advantage of it, but it
> shouldn't be too difficult for others to implement if they wanted since
> they're fairly close to one another (in clk_change_rate()).
> 
> * switched to using new determine_rate op rather than adding an argument
>   to round_rate.
> * moved mux implementation into a single helper which should be usable
>   from more complex clocks which can mux.
> * rewrite main implementation so that no changes are made until after
>   the PRE notifications have been sent, and in a way that should ensure
>   correct notifications without duplicates, and I think should be safe
>   in the event of a notification failing.
> * various tidy ups and fixes.
> 
> James Hogan (5):
>   clk: abstract parent cache
>   clk: move some parent related functions upwards
>   clk: add support for clock reparent on set_rate
>   clk: add CLK_SET_RATE_NO_REPARENT flag
>   clk: clk-mux: implement remuxing on set_rate
> 
>  Documentation/clk.txt                  |  46 ++--
>  arch/arm/mach-imx/clk.h                |   5 +-
>  drivers/clk/clk-mux.c                  |   1 +
>  drivers/clk/clk.c                      | 420 +++++++++++++++++++++------------
>  drivers/clk/mmp/clk-mmp2.c             |  39 ++-
>  drivers/clk/mmp/clk-pxa168.c           |  40 ++--
>  drivers/clk/mmp/clk-pxa910.c           |  31 ++-
>  drivers/clk/mxs/clk.h                  |   4 +-
>  drivers/clk/samsung/clk-exynos-audss.c |   6 +-
>  drivers/clk/samsung/clk.h              |   2 +-
>  drivers/clk/spear/spear1310_clock.c    | 179 +++++++-------
>  drivers/clk/spear/spear1340_clock.c    |  97 ++++----
>  drivers/clk/spear/spear3xx_clock.c     |  57 +++--
>  drivers/clk/spear/spear6xx_clock.c     |  35 +--
>  drivers/clk/sunxi/clk-sunxi.c          |   3 +-
>  drivers/clk/tegra/clk-tegra114.c       |  36 ++-
>  drivers/clk/tegra/clk-tegra20.c        |   6 +-
>  drivers/clk/tegra/clk-tegra30.c        |  33 ++-
>  drivers/clk/versatile/clk-vexpress.c   |   4 +-
>  drivers/clk/zynq/clkc.c                |  86 ++++---
>  include/linux/clk-private.h            |   3 +
>  include/linux/clk-provider.h           |  12 +
>  22 files changed, 692 insertions(+), 453 deletions(-)
> 
> -- 
> 1.8.1.2
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