On Tue, Apr 19, 2011 at 2:39 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Tuesday 19 April 2011, Andrei Warkentin wrote: > >> So maybe this should be a blacklist for known bad cards. And the >> entire support should be a "default-N" compile option for MMCs (not >> SDs). That way someone who just does an "make oldconfig" will see >> "CONFIG_MMC_BLK_CMD23 - I/O performance improvement for newer eMMC >> cards, may cause degradation on older cards". What do you think? > > I'm not sure if I understand the distinction between MMC and SD > here. Do you suggest we always enable it for SD but make it compile-time > selected for MMC? I did, because CMD23 support on SDs is a new feature mandatory on UHS104 cards. However, I guess no matter what you do, it's going to break something. Right now I'm only aware of Toshiba perf regressions. > > I generally argue against compile time options. A distribution > integrator needs to choose a reasonable default, and giving them > an option makes it possible to get it wrong. > > I believe the best way would be trying to warn people against > regressions while going forward with this enabled unconditionally, > unless we hear back from people that actually got regressions. Alright. Then I'll just blacklist the known-affected Toshiba cards for now, and we'll keep it enabled by default. > > We could perhaps key enabling the feature by the production date > on the card, so it only gets turned on for new cards. > Unfortunately, date by itself is meaningless too (current Toshiba eMMCs) A -- 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
