[PATCH v3 2/4] clk: add support for clock reparent on set_rate

On 05/15/13 06:41, James Hogan wrote:

Add core support to allow clock implementations to select the best
parent clock when rounding a rate, e.g. the one which can provide the
closest clock rate to that requested. This is by way of adding a new
clock op, determine_rate(), which is like round_rate() but has an extra
parameter to allow the clock implementation to optionally select a
different parent clock. The core then takes care of reparenting the
clock when setting the rate.

The parent change takes place with the help of two new private data
members. struct clk::new_parent specifies a clock's new parent (NULL
indicates no change), and struct clk::new_child specifies a clock's new
child (whose new_parent member points back to it). The purpose of these
are to allow correct walking of the future tree for notifications prior
to actually reparenting any clocks, specifically to skip child clocks
who are being reparented to another clock (they will be notified via the
new parent), and to include any new child clock. These pointers are set
by clk_calc_subtree(), and the new_child pointer gets cleared when a
child is actually reparented to avoid duplicate POST_RATE_CHANGE
notifications.

Each place where round_rate() is called, determine_rate is checked first
and called in preference, passing NULL to the new parent argument if not
needed (e.g. in __clk_round_rate).

That's annoying. Even if we don't care about the pointer in
clk_round_rate(), this requires the ops to check for NULL before
assigning the pointer. Why not just pass an unused pointer that the ops
can assign all the time?

 This restructures a few of the call
sites to simplify the logic into if/else blocks.

A new __clk_set_parent_no_recalc() is created similar to
clk_set_parent() but without calling __clk_recalc_rates(). This is for
clk_change_rate() to use, where rate recalculation and notifications are
already handled.

Signed-off-by: James Hogan <redacted>
Cc: Mike Turquette <redacted>
Cc: linux-arm-kernel at lists.infradead.org

With the above change you can add

Reviewed-by: Stephen Boyd <redacted>

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