Messages in this thread | | | Date | Sat, 28 Jan 2017 23:39:11 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH] clk: add more managed APIs |
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On Sat, Jan 28, 2017 at 01:44:35PM -0800, Guenter Roeck wrote: > On 01/28/2017 11:22 AM, Dmitry Torokhov wrote: > >Guenter, I know you are a coccinelle wizard, can you cook a script that > >can find current users of clk_enable() in probe paths? Then we can make > >informed decision on devm_clk_enable. > > > > Questionable use: > drivers/input/keyboard/st-keyscan.c
clk_enable() without preceding clk_prepare() - buggy.
> > clk_enable() in probe, clk_disable() in remove: > drivers/i2c/busses/i2c-tegra.c
Could be converted to use clk_prepare_enable() or clk_prepare() depending on i2c_dev->is_multimaster_mode in the initialisation path (and their devm_* equivalents.)
> drivers/media/platform/exynos4-is/fimc-core.c > drivers/media/platform/exynos4-is/mipi-csis.c
Looks like it does a sequence of:
devm_clk_get() clk_prepare() clk_set_rate() clk_enable()
which seems a little wrong - clk_set_rate() should be before clk_prepare() if you care about not having the clock output. Remember that clk_prepare() _may_ result in the clock output being enabled. So these two look buggy, and when fixed could use devm_clk_prepare_enable().
> drivers/thermal/spear_thermal.c
clk_enable() without a preceding clk_prepare(). Buggy driver.
> drivers/usb/musb/am35x.c
Ditto.
> drivers/usb/musb/davinci.c
Ditto.
> Not that many. A quick browse suggests that clk_enable()/clk_disable() > is more commonly used to temporarily enable the clock while needed.
So out of all those, there's probably only _one_ which is legit - the rest are all technically buggy.
Given that, I'd say there's real reason _not_ to provide devm_clk_enable() to persuade people to use the correct interfaces in the probe path.
-- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
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