On Thu, Mar 10, 2011 at 3:54 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Thursday 10 March 2011 21:45:07 Andrei Warkentin wrote: >> > We can pre-initialize the page size to some common value >> > (e.g. 16 KB for 4GB or larger cards, 4 KB for smaller than >> > 4 GB), and use quirks to override it for cards where we >> > know it's different. >> > >> >> Even better. We have the "super page size" in the EXT_CSD. For example >> for Sandisk it's 16KB, Toshiba is reporting 32KB, but we know that's >> not right... > > Ok, that sounds good. I don't think we have anything like this > for SD cards though, so we'd still need to make some reasonable > assumption there. > > The one thing we know is that all SD cards should support writes of > 32KB alignment, because that is the largest cluster size supported > by FAT16 and FAT32. I have experimentally shown that most cards > can reasonably do 16KB, and only few modern cards can do smaller > than that. > > I also don't know what the effect of setting physical_block_size > and/or io_min is, possibly it no longer works if they are larger > than the MMU page size. Need to try this. The other thing is figuring out the default size limit for when the page align should be performed. I suppose it's safe enough to set it to 1.5 size the super_page_size. But that number came from the Toshiba card tests. Or it could be unbounded by default. I'd rather do the later. 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
