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.
--
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