Hi Mike et al,
El 15/12/13 01:51, Mike Turquette escribió:
clk_set_phase has been proposed before and now may be the time to add
it. There are two things that need to be addressed:
1) what are the values for the phase? This needs to work for others that
must set clk phase, so we need to consider all those requirements before
making a new function declaration in clk.h
2) is setting a clock's phase something done dynamically? Put another
way, does the same clock has it's phase set multiple times while the
system is running? For static configuration that only happens during
initialization we do not need a new API. The clock driver can handle it
privately. For dynamic operations though we likely need a new API.
We on sunxi also need this for our (not yet merged) MMC driver; we
currently have it implemented as an exported
void clk_sunxi_mmc_phase_control(struct clk_hw *hw, u8 sample, u8 output)
that takes the MMC clock (and only the MMC clock) and does the setup
(it's basically configuring two values, "sample" and "output", into the
clock register). I really don't know what does this do/why is it
required/when is it used; I'm cc'ing Hans and David who can hopefully
explain that part.
I also saw a similar requirement from the gmac people (on cc too), who
needed to set the phy type (or something like that) on one of the clock
registers; so I'm thinking maybe a generic "tune something" approach
that lets users configure some clock-dependent, arbitrary aspect of the
clock is the way forward. Otherwise, we're going to end up bloating the
clock framework with a lot of callback pointers that are going to be
used in one or two clocks out of potentially hundreds on the whole system.
Cheers,
Emilio
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