On 09/03/2014 02:13 AM, Mike Turquette wrote:
Quoting Tomeu Vizoso (2014-09-01 08:34:34)@@ -1633,6 +1636,13 @@ int clk_provider_set_rate(struct clk_core *clk, unsigned long rate) /* prevent racing with updates to the clock topology */ clk_prepare_lock();+ hlist_for_each_entry(clk_user, &clk->per_user_clks, child_node) { + rate = max(rate, clk_user->floor_constraint); + + if (clk_user->ceiling_constraint > 0) + rate = min(rate, clk_user->ceiling_constraint);A ceiling_constraint from consumer_A could be less than a floor_constraint from consumer_B. What should we do in this case? In the code above the ceiling_constraint will always win. Is that by design? We should document that behavior in Documentation/clk.txt. This is the right place to check for the aforementioned corner case, since we not only care about a single consumer having sane constraints (e.g. min < max) but also mixing constraints across consumers.
Yeah. I think I lean towards first applying all floors, then applying all ceilings. Because hardware damage could happen if a ceiling from thermal isn't applied because of a bug in some other driver.
This also has the advantage of being deterministic, when with the current approach the result depends on the order in which the per-user clocks are iterated.
However ...+ } + /* bail early if nothing to do */ if (rate == clk_provider_get_rate(clk)) goto out; @@ -1699,6 +1709,24 @@ int clk_set_rate(struct clk *clk_user, unsigned long rate) } EXPORT_SYMBOL_GPL(clk_set_rate); +int clk_set_floor_rate(struct clk *clk_user, unsigned long rate) +{ + struct clk_core *clk = clk_to_clk_core(clk_user); + + clk_user->floor_constraint = rate; + return clk_provider_set_rate(clk, clk_provider_get_rate(clk)); +} +EXPORT_SYMBOL_GPL(clk_set_floor_rate); + +int clk_set_ceiling_rate(struct clk *clk_user, unsigned long rate) +{ + struct clk_core *clk = clk_to_clk_core(clk_user); + + clk_user->ceiling_constraint = rate; + return clk_provider_set_rate(clk, clk_provider_get_rate(clk)); +} +EXPORT_SYMBOL_GPL(clk_set_ceiling_rate);... we should probably sanity-check constraints here to make sure that ceiling_rates for a given consumer are higher than floor_constraints for that same consumer. It's a bit extra overhead but a WARN would probably be helpful in this case.
Sounds like a good idea to me, will do. Thanks, Tomeu
Rest of the patch looks good. Regards, Mike
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