Messages in this thread | | | Date | Tue, 1 Feb 2011 16:18:46 +0100 | From | Uwe Kleine-König <> | Subject | Re: Locking in the clk API, part 2: clk_prepare/clk_unprepare |
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On Tue, Feb 01, 2011 at 02:39:32PM +0000, Russell King - ARM Linux wrote: > On Tue, Feb 01, 2011 at 03:18:37PM +0100, Uwe Kleine-König wrote: > > On Tue, Feb 01, 2011 at 01:15:12PM +0000, Russell King - ARM Linux wrote: > > > On Tue, Feb 01, 2011 at 11:54:49AM +0100, Uwe Kleine-König wrote: > > > > Alternatively don't force the sleep in clk_prepare (e.g. by protecting > > > > prepare_count by a spinlock (probably enable_lock)) and call clk_prepare > > > > before calling clk->ops->enable? > > > > > > That's a completely bad idea. I assume you haven't thought about this > > > very much. > > Right, but I thought it a bit further than you did. Like the following: > > > > int clk_prepare(struct clk *clk) > > { > > int ret = 0, first; > > unsigned long flags; > > > > spin_lock_irqsave(&clk->enable_lock, flags); > > if (clk->flags & CLK_BUSY) { > > /* > > * this must not happen, please serialize calls to > > * clk_prepare/clk_enable > > */ > > How do different drivers serialize calls to clk_prepare? Are you > really suggesting that we should have a global mutex somewhere to > prevent this? yeah, didn't thought about multiple consumers, so (as Jeremy suggested) the right thing is to sleep until CLK_BUSY is cleared.
Best regards Uwe
-- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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