On 16 September 2013 22:57, Guennadi Liakhovetski <g.liakhovetski@xxxxxx> wrote: > Hi Ulf > > On Mon, 16 Sep 2013, Ulf Hansson wrote: > >> According to the eMMC/SD/SDIO specs the VDD voltage level must not be changed >> during the initialization, without a complete power cycle of the card. >> >> Before this patchset, some host drivers were trying to change voltage level >> at MMC_POWER_ON state, which is also what the protocol layer advised them to. >> This was not correctly done and is the reason to why quite messy code in >> the protocol layer has been needed, to handle a re-initialization sequence, >> typically triggered from a power_restore or resume. >> >> I have tried to make each patch in the patchset as small and separate as >> possible, surely the is room for improvments. Any suggestions are appreciated. >> >> An important note; MMC_CAP2_FULL_PWR_CYCLE, will need to be set by a host >> to tell the protocol layer that the host is able to perform a complete power >> cycle. Thus the protocol layer will try to negotiate the lowest possible VDD >> voltage level between the card and host. Hi Guennadi, > > I've got a question to this one. You mean a power cycle of a card, right? Correct! > What if the card power is supplied by a regulator. How do you tell whether > you can power cycle it or not? Maybe you can theoretically switch that > regulator - sometimes. On other occasions other users might be preventing > it from really powering off. Do you really need a guarantee, that every > time you issue a power down .set_ios() the card will really be switched > off? I don't see how this can be possible in my example? Yes, we need a guarantee to be able to conform to the specs. In one of my cases I am also using a regulator, but from a board configuration point of view I know I am the only user on this regulator, thus I can be sure I can switch it off when I want. I see your point though, and I am not sure how to adapt to this configuration. I suggest you to not set the MMC_CAP2_FULL_PWR_CYCLE for that mmc host - unless you can find a way to make sure you can cut and restore power when needed. Kind regards Ulf Hansson > > Thanks > Guennadi > >> >> >> Ulf Hansson (7): >> mmc: core: Let mmc_power_up|cycle take ocr as parameter >> mmc: core: Let mmc_set_signal_voltage take ocr as parameter >> mmc: core: Remove unnecessary retry mechanism at SDIO attach >> mmc: core: Cleanup code for setting ocr mask for SDIO >> mmc: core: Move cached value of the negotiated ocr mask to card >> struct >> mmc: core: Prevent violation of specs while initializing cards >> mmc: core: Collect common code for card ocr validation >> >> drivers/mmc/core/core.c | 66 +++++++++++++++++-------------------- >> drivers/mmc/core/core.h | 6 ++-- >> drivers/mmc/core/mmc.c | 29 +++++----------- >> drivers/mmc/core/sd.c | 41 +++++++---------------- >> drivers/mmc/core/sdio.c | 82 ++++++++++++++-------------------------------- >> include/linux/mmc/card.h | 1 + >> include/linux/mmc/host.h | 1 - >> 7 files changed, 79 insertions(+), 147 deletions(-) >> >> -- >> 1.7.9.5 >> >> -- >> 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 >> > > --- > Guennadi Liakhovetski, Ph.D. > Freelance Open-Source Software Developer > http://www.open-technology.de/ -- 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
