On 1/15/2013 9:02 PM, Mike Turquette wrote: > Quoting Afzal Mohammed (2013-01-15 05:44:36) >> LCDC IP has a clock divider to adjust pixel clock, this limits pixel >> clock range to fck/255 - fck/2(fck - rate of input clock to LCDC IP). >> In the case of AM335x, where this IP is present, default fck is not >> sufficient to provide normal pixel clock rates, hence rendering this >> driver unusable on AM335x. >> >> If input clock too is configurable, allowable range of pixel clock >> would increase. Here initially it is checked whether with present fck, >> divider in IP could be configured to obtain required rate, if not, >> fck is adjusted. This makes it usable on AM335x. >> >> Note: >> A better (if allowable) solution may be to represent clock divider in >> LCDC IP as a basic divider clock - the one defined in common clock >> framework. But for this to happen, all the platform's using this driver >> should be using common clock framework (DaVinci is yet to be converted >> to use common clock framework). And it has to be determined whether >> common clock framework allows this kind of a clock modelling inside a >> driver and for this to be part of clock tree. Advantage of doing so >> would be better resolution for pixel clock, even though without this >> existing use cases are working properly. Or another extreme alternative >> would be to replicate clk-divider of common clock framework inside the >> driver, but that probably is not preferred and not worth as it would be >> duplication and without much advantage to existing users. >> > > Afzal, > > Modeling the divider inside your IP block as a clock is supported in the > common clock framework. Linking up these sorts of clocks to the clock > tree was one of the original design goals of CCF. > > Regarding DaVinci: converting that platform over to use CCF would be the > best approach. This is work in progress. There are patches that have been posted. Work has been slow on this though due to lack of bandwidth. > An alternative would be that you could break > single-image boot for AM335x and DaVinci, by having AM335x use CCF and > DaVinci use the legacy clock framework. From the LCDC driver's Single image for DaVinci and AM335x is not possible anyway since ARMv5 and ARMv6+ cannot be supported in a single image. > perspective this should not matter and is indeed the purpose of the > clk.h api and clkdev interfaces, however looking at this driver I can > see there would still be a lot ifdef-ery going on... better to just > convert everything over to CCF. Waiting for DaVinci CCF to complete will be too long a wait. Probably convert to CCF just for AM335x ATM. There would be some ifdef'ry but hopefully that need not be inside function bodies. Would have to see the implementation, I guess. Thanks, Sekhar -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
