On 10/02/17 09:12, Ulf Hansson wrote: > On 30 September 2017 at 17:39, Bernd Edlinger <bernd.edlinger@xxxxxxxxxx> wrote: >> >> Needs external logic to multiplex the clock signal, >> which is controlled by a GPIO output pin. >> >> Only the selected SD card receives the clock, >> while the other SD card's clock is forced to LOW. >> DATA and CMD lines can be connected to both SD cards. >> >> On warm-start UBOOT should use a sequence of >> CMD12 and CMD7 with RCA=0 to force any active SD card >> to stop transmission and release the DATA bus. > > I doubt that is sufficient to support multiple slots. > A hardware exists and AFAICT works as expected, with bus speeds up to 50 MHz. We have a use case with internal peripherals. > Sometimes the mmc core needs to perform a sequence of operations > towards *one* host/card and that must be done in guaranteed manner, to > that no other operations are performed for another card/host > in-between. > Could you please elaborate on this? > Perhaps if you are lucky you may get something that is very fragile to > work, but in the end I think the core needs to play along. Moreover, > dw_mmc has recently removed its multiple slot support - simply because > the complexity wasn't worth it. > I was not overly happy to see this removed, when I re-based to current master :-( Bernd-- 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
