[PATCH 1/2] clk: bcm: Support rate change propagation on bcm2835 clocks

Eric Anholt eric at anholt.net
Fri Dec 2 11:01:09 PST 2016

Boris Brezillon <boris.brezillon at free-electrons.com> writes:

> Some peripheral clocks, like the VEC (Video EnCoder) clock need to be set
> to a precise rate (in our case 108MHz). With the current implementation,
> where peripheral clocks are not allowed to forward rate change requests
> to their parents, it is impossible to match this requirement unless the
> bootloader has configured things correctly, or a specific rate has been
> assigned through the DT (with the assigned-clk-rates property).
> Add a new field to struct bcm2835_clock_data to specify which parent
> clocks accept rate change propagation, and support set rate propagation
> in bcm2835_clock_determine_rate().
> Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>

A possible simplification would be to limit VEC to only PLLH_AUX, since
that was how the HW designers intended it to be used.  Then you could
just have SET_RATE_PARENT flag, rather than the bitfield.

Still, this seems to be correct and fixes the bug.  Both patches are:

Reviewed-by: Eric Anholt <eric at anholt.net>
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