On Sat, May 15, 2010 at 3:02 AM, Dmitry Shmidt <[email protected]> wrote: > Hi Andrew, > > wl1251 has some HW problem for ELP register that demands to do > something like "write during read" in order > not to loose bits from this register during simple read. > Fortunately it was enough just to add low 8 bits previous register > value to the cmd.args during read operation > and SD Controller will behave as needed. And it was tested on real > wl1251 device that is used in G1 and MyTouch. > > However, patch author for some reason is using WRITE operation instead of > READ. >>>> ret = mmc_io_rw_direct(func->card, 1, func->num, addr, b, &val); >>>> 1 means WRITE > > Maybe in case of wl1251 HW it is not important - to write during read, > or to read during write, but the problem in wl1251 was during ELP > register READ operation, so I do not understand why author used WRITE > flag.
Well like you said, 'wl1251 [...] demands to do something like "write during read"', and SDIO spec provides exactly this functionality with the RAW flag (quoting SDIO spec): "If this bit [RAW] is set to 1 and the R/W flag is set to 1, then the command shall read the value of the register after the write. This is useful to allow writing to a control register and reading the status at the same address." If you pass WRITE flag and a pointer for read value to mmc_io_rw_direct(), it sets the R/W and RAW bits in the CMD52 request. According to my tests wl1251 actually ignores both R/W and RAW flags, but by the looks of it it is expecting the RAW request. With my patch we can add a function that both conforms the SDIO spec and suits wl1251 hardware. Does that make sense to you? -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
