On Monday, July 20, 2015 at 11:23:39 AM, Cyrille Pitchen wrote: > Hi Marek, Hi! > Le 16/07/2015 19:44, Marek Vasut a écrit : > > On Thursday, July 16, 2015 at 05:27:51 PM, Cyrille Pitchen wrote: > > > > Hi! > > > >> Both the SPI controller and the NOR flash memory need to agree on the > >> number of dummy cycles to use for Fast Read commands. For Spansion > >> memories, this number of dummy cycles is not given directly but through > >> a so called "latency code". > >> The latency code can be found into the memory datasheet and depends on > >> the SPI clock frequency, the Fast Read op code and the Single/Dual Data > >> Rate mode. > > > > Shouldn't you be able to derive the latency code from the above > > information, which you already know then ? > > Yes I agree with you; this could have been done adding static tables inside > the driver instead of creating a new DT property dedicated to Spansion > memories. OK, I see now. The latency code can not be calculed from "SPI clock frequency, the Fast Read op code and the Single/Dual Data Rate mode" easily, you need to index into some table to obtain some ad-hoc value. Got it. Sorry for the noise! > When I wrote this patch, I had a close look at the s25fl512s datasheet but > only overviewed few datasheets for other Spansion QSPI flash memories. So > I don't know whether a single latency code table could be shared among all > Spansion memories or many tables should be added to support different > memory models. > > That's why I've chosen to add a dedicated DT property to support Spansion > memories as it avoids to add tables to guess the proper latency code to be > used. I thought it would be more flexible. > > Maybe I will remove the support of Spansion QSPI memories from this series > for now. Their support can still be implemented later. > > Anyway, thanks for your review :) Let's wait for more comments :) Best regards, Marek Vasut -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
