Messages in this thread | | | From | Jeremy Kerr <> | Subject | Re: Locking in the clk API, part 2: clk_prepare/clk_unprepare | Date | Tue, 1 Feb 2011 22:40:37 +0800 |
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Hi Uwe,
Thanks for the feedback, I'm not sure I like the more complex approach though:
> 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 > */ > ret = -EBUSY; > goto out_unlock;
Why is this an error? Two separate drivers may be clk_prepare()-ing at the same time, which should be acceptable. Both calls should block until the prepare is complete.
> } > first = clk->prepare_count++ == 0; > if (first) > clk->flags |= CLK_BUSY; > spin_unlock_irqrestore(&clk->enable_lock, flags); > > if (!first) > return 0; > > if (clk->ops->prepare) { > might_sleep(); > ret = clk->ops->prepare(clk); > } > > spin_lock_irqsave(&clk->enable_lock, flags); > clk->flags &= ~CLK_BUSY; > if (ret) > clk->prepare_count--; > out_unlock: > spin_unlock_irqrestore(&clk->enable_lock, flags); > > return ret; > }
Cheers,
Jeremy
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