Dinh, On Fri, Apr 10, 2015 at 6:56 AM, <dinguyen@xxxxxxxxxxxxxxxxxxxxx> wrote: > From: Dinh Nguyen <dinguyen@xxxxxxxxxxxxxxxxxxxxx> > > The ciu_clk(Card Interface Unit Clock) on the SoCFPGA platform has a fixed > divider of 4. Add the fixed clock divide code in the platform's clock > setup code. It might actually be better to do this a different way for SoCFPGA. I sorta wish we had done it differently for Rockchip as well, but at this point you end up with the complexity of changing device tree bindings in conjunction with code and it gets ugly. Specifically, you've probably got the following clocks: SD_prediv = 400MHz -> SD postdiv = 100MHz -> SD sample = 100MHz, shifted -> SD drive = 100MHz, shifted Right now you're specifying "SD_prediv" as the SD card clock. If you instead expose "SD postdiv" as a new clock (from your clock driver) that is "SD prediv" divided by 4 then you'll magically get all the behavior that you want with no modifications to dw_mmc. Just make sure that "SD postdiv" passes on rate changes to its parent (that's just a flag in the common clock framework). At some point in time you'll also want to expose the sample and drive clocks once you get UHS modes working. Alexandru posted some patches for this a while ago to support tuning in dw_mmc using just drive and sample clocks, but the patch still needed some more work. Either he or I will probably pick it up again soon. -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
