Hi Ulf, 2014-11-06 10:38 GMT+01:00 Ulf Hansson <ulf.hansson@xxxxxxxxxx>: > [...] > >>> >>> Earlier we used always used MMC_BUSMODE_PUSHPULL, now it will depend on "spi". >> >> The JEDEC spec says that in device identification mode the bus should >> be open-drain and not push-pull. So this way should be compliant to >> the spec, right? Unfortunately, I will require help in testing this on >> a proper eMMC. > > For MMC yes, but you will break SD/SDIO in this patch. > > The default bus mode at initialization needs to be > MMC_BUSMODE_PUSHPULL, since that's required by the SD/SDIO spec. > > The MMC cards are being initialized after SD and SDIO, which means a > switch to MMC_BUSMODE_OPENDRAIN is done in mmc_attach_mmc(). > Additionally, to handle resume of MMC cards, mmc_init_card() also do a > switch to MMC_BUSMODE_OPENDRAIN. > >> >> I can't find anything in the JEDEC or the SD spec about bus mode in >> SPI mode though. However, this behavior is not changed by this patch, >> so we should be safe. > > SPI mode has been removed from the eMMC spec. > > The SD spec doesn't have open drain mode but do support SPI mode. That > tells me that we should keep using MMC_BUSMODE_PUSHPULL for SPI mode. Thank you for explaining this. So I think we should be OK by always choosing MMC_BUSMODE_PUSHPULL, because for MMC cards mmc_init_card is called from mmc_power_restore which is called after the hw_reset. Will post a v3 of this patch. //Johan -- 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
