On Thu, 28 Oct 2010, Paul Mundt wrote: > On Wed, Oct 27, 2010 at 06:24:26PM +0200, Guennadi Liakhovetski wrote: > > On ap4evb PLLC2 is used as a parent clock for the HDMI clock. To configure the > > HDMI clock with the highest precision this patch scans all available PLLC2 > > frequencies and picks up the best one. > > > > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx> > > So, what exactly does ap4evb_clk_optimize() do that you can't already do > with either clk_rate_table_round() or clk_rate_div_range_round()? No, it does something pretty different: it selects the best _parent_ frequency to optimize that of the _child_. So, it actually tells you "to configure your clock as close as possible to frequency X you have to reconfigure its parent with frequency Y." Which I don't think any of the aforementioned functions does. > I really don't want to see this sort of rate table access going on > outside of the clock framework itself, so if we need to add or extend an > existing helper for a new usecase then that is highly preferable to > constantly reinventing things. Well, there is a reason, why this is marked an "RFC":-) I also don't like very much touching clock internals in platform code, but in a way it is specific for each case. This implementation only works for clocks, whose divisors are integer numbers in a certain range (without holes). Ok, with clk_get_parent() the other two callbacks .clk_set_rate_parent() and .clk_get_rate_parent() are automatically not needed, which is good! And I would be happy to try to convert the ap4evb_clk_optimize() function into a generic helper too, if we reach such an agreement. Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
