Hein_Tibosch <hein_tibosch@xxxxxxxx> wrote: > >> We've now submitted one fix each, mine was similar to yours [1] but there's been movement on Hein's more comprehensive patch recently [2]. I don't know who's supposed to be merging MMC patches atm, Chris Ball added on CC on a hunch. > > Thanks for the references. IMO Hein's patch is overkill. There is > > absolutely no reason why 200 kHz should be a problem on any setup, and > > I haven't found any indication in any discussions that it is. > > > > I have also seen situations in which the SD will only start up at 180 Khz > or lower. Ok, so my patch would obviously not fix those. Could you tell me more about those situations? What kind of board are you running at, etc? > IMO my patch is indeed a bit of an overkill (the amount of code changed), > I'd rather see a patch like yours or Ben's, but settings fOD at 100 or 50 Khz. I guess 100 kHz would make sense. 50 kHz is not allowed according to the SD card spec. Another solution might be to introduce a new field, f_max_od, which the host controller driver could use to limit the bus frequency in open drain mode. > It was Pierre who suggested to try several frequencies[1]: most systems will start > using 400 Khz (so they won't suffer any loss of performance) and in some rare > cases, the SD will only be identified at 100 Khz (which does happen, sometimes) I think any performance hit in open drain mode is not likely to be noticeable, as it is only used for a couple of commands. The only thing that really matters for performance is push-pull mode, where too strong pull-ups might cause problems at high speed. But if there really are cards that have problems at 100 kHz, I guess your patch might be the best bet. Haavard -- 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
