Messages in this thread | | | Date | Thu, 31 May 2012 12:09:46 -0700 | From | Mike Turquette <> | Subject | Re: [RFC PATCH] clk: add extension API |
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On 20120530-13:28, Stephen Boyd wrote: > On 05/30/12 12:40, Mike Turquette wrote: > > I also wonder if exposing some of these knobs should be done in the > > basic clock types. Meaning that instead of having additional calls in > > the clk.h API those calls could be exposed by the basic clock types that > > map to the actions. > > What do you mean by basic clock types that map to actions? Perhaps an > example? >
No exmaples to give, just tossing out ideas.
> > > > The question that needs to be answered is this: do generic drivers need > > access to these additional functions (clk.h) or just the platform code > > which implements some of the clock logic (basic clock types & > > platform-speciic clock types). > > At least for tegra it looks like they need reset assertion and > deassertion in generic drivers. > > $ git grep tegra_periph_reset_assert > arch/arm/mach-tegra/clock.c:void tegra_periph_reset_assert(struct clk *c) > arch/arm/mach-tegra/clock.c:EXPORT_SYMBOL(tegra_periph_reset_assert); > arch/arm/mach-tegra/include/mach/clk.h:void tegra_periph_reset_assert(struct clk *c); > arch/arm/mach-tegra/pcie.c: tegra_periph_reset_assert(tegra_pcie.pcie_xclk); > arch/arm/mach-tegra/pcie.c: tegra_periph_reset_assert(tegra_pcie.afi_clk); > arch/arm/mach-tegra/pcie.c: tegra_periph_reset_assert(tegra_pcie.pex_clk); > arch/arm/mach-tegra/pcie.c: tegra_periph_reset_assert(tegra_pcie.pcie_xclk); > arch/arm/mach-tegra/pcie.c: tegra_periph_reset_assert(tegra_pcie.afi_clk); > arch/arm/mach-tegra/powergate.c: tegra_periph_reset_assert(clk); > drivers/i2c/busses/i2c-tegra.c: tegra_periph_reset_assert(i2c_dev->clk); > drivers/input/keyboard/tegra-kbc.c: tegra_periph_reset_assert(kbc->clk); > drivers/staging/nvec/nvec.c: tegra_periph_reset_assert(nvec->i2c_clk); >
Ok, this is good to know. The same sort of thing is achieved via runtime pm and the hwmod framework in OMAP code. I had given similar feedback to Andrew Lunn for using clk_prepare/clk_unprepare to power down the PHY for some of his IP blocks. I don't think that the clock framework should be used for that and this clk_reset(...) stuff seems similar.
Like Benoit, I am partial to associating these actions to module-level APIs, not necessarily clock-level APIs.
A yardstick to determine whether or not the clock framework is the right place for a _reset() function might be whether or not it will change the values of struct clk's members. If we had a clk_reset(...) call it would clearly bang some bits in a register via clk->ops->reset ... but what data would it change in struct clk? Adjust the rate to 0? Reset prepare_count and enable_count to 0?
If it doesn't actually change any of the bookkeeping or accounting in the clock framework then it might be a clue that the clock framework isn't the best place for this API.
Thanks, Mike
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