Hi Stephen,
2016-08-05 6:25 GMT+09:00 Stephen Boyd <sb...@codeaurora.org>: > +Rob in case he has any insight > > On 07/09, Masahiro Yamada wrote: >> Hi. >> >> I think the current code allows to add >> clk_providers multiple times against one DT node. >> >> Are there cases that really need to do so? > > If we have clk drivers that have a device driver structure and > also use CLK_OF_DECLARE then we could get into a situation where > they register two providers for the same device node. I can't > think of any other situation where this would happen though. What is the benefit for splitting one clock device into CLK_OF_DECLARE() and a platform_driver? If we go this way, I think we need to fix the current code. of_clk_add_provider() calls of_clk_del_provider() in its failure path. Notice of_clk_del_provider() unregister all the providers associated with the device node. So, if of_clk_add_provider() fails to register a platform driver, it may unregister another provider added by OF_CLK_DECLARE(). Some platform drivers call of_clk_del_provider() in a .remove callback, so the same problem could happen. Why does of_clk_del_provider() take (struct device_node *np) ? Shouldn't it take (struct of_clk_provider *cp)? > It used to return the last provider's error, but I accidentally > changed that behavior when adding clk_hw providers in commit > 0861e5b8cf80 (clk: Add clk_hw OF clk providers, 2016-02-05). > Nobody seems to have complained though, so you're the first to > have reported this. If we allow multiple OF-providers for one device node, I think any error should be treated as EPROBE_DEFER, i.e. the current code is good. The scenario is: - Clocks with ID 0 thru 3 are provided by CLK_OF_DECLARE() - Clocks with ID 4 thru 9 are provided by a platform driver. What if a clock consumer requests the clk ID 5 after CLK_OF_DECLARE(), but before the clk platform driver is registered? If the clock consumer gets the last provider's error (-EINVAL returned from CLK_OR_DECLARE one in this case) it will lose a chance to retry it after clocks from a platform driver are registered. A bit nasty... -- Best Regards Masahiro Yamada
