On Mon, Feb 24, 2014 at 05:22:43PM +0100, Maxime Ripard wrote:
> Right now, AHB is an indirect child clock of the CPU clock. If that happens to
> change, since the CPU clock has no other consumers declared in Linux, it would
> be shut down, which is not really a good idea.
>
> Prevent this by forcing it enabled.
>
> Signed-off-by: Maxime Ripard <maxime.rip...@free-electrons.com>
> ---
> drivers/clk/sunxi/clk-sunxi.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/clk/sunxi/clk-sunxi.c b/drivers/clk/sunxi/clk-sunxi.c
> index 23baad9..cedaf4b 100644
> --- a/drivers/clk/sunxi/clk-sunxi.c
> +++ b/drivers/clk/sunxi/clk-sunxi.c
> @@ -1301,6 +1301,14 @@ static void __init sunxi_clock_protect(void)
> clk_prepare_enable(clk);
> clk_put(clk);
> }
> +
> + /* CPU clocks - sun6i */
> + clk = clk_get(NULL, "cpu");
> + if (!IS_ERR(clk)) {
> + clk_prepare_enable(clk);
> + clk_put(clk);
> + }
This is broken. I'm not sure what's difficult to grasp about the concept
of "while a clock is in use, you should keep a reference to that clock".
That implies that if you get a clock, and then enable it, you don't
put the clock until you've disabled it.
The only reason the core doesn't check for this kind of thing is that
a clock may be shared, so it's entirely possible for a correctly written
driver to have a clock which is still enabled at put time - but enabled
by an entirely different driver.
However, that's no excuse for this kind of sloppiness.
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