Hello Russell, El 24/02/14 13:30, Russell King - ARM Linux escribió:
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.ripard@xxxxxxxxxxxxxxxxxx> --- 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.
Why is this so? Can't a clock be left enabled while nobody has a reference to it? I have looked around in Documentation/ (rather quickly I must say) and have not found any explicit mention that it is required to keep a reference to the clock while it's enabled. I'd appreciate it if you could explain this a bit more verbosely or point me to the relevant documents.
For what it's worth, I've seen this same pattern on enable/disable_clock() on drivers/base/power/clock_ops.c as well.
Cheers, Emilio -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
