On Thu, 2016-05-12 at 13:29 +0300, Adrian Hunter wrote: > On 12/05/16 10:00, Chaotian Jing wrote: > > On Wed, 2016-05-11 at 10:50 +0300, Adrian Hunter wrote: > >> On 04/05/16 09:54, Chaotian Jing wrote: > >>> Per JEDEC spec, it is not recommended to use CMD13 to get card status > >>> after speed mode switch. below are two reason about this: > >>> 1. CMD13 cannot be guaranteed due to the asynchronous operation. > >>> Therefore it is not recommended to use CMD13 to check busy completion > >>> of the timing change indication. > >>> 2. After switch to HS200, CMD13 will get response of 0x800, and even the > >>> busy signal gets de-asserted, the response of CMD13 is aslo 0x800. > >>> > >>> this patch drops CMD13 when doing speed mode switch, if host do not > >>> support MMC_CAP_WAIT_WHILE_BUSY and there is no ops->card_busy(), > >>> then the only way is to wait a fixed timeout. > >> > >> This looks like it should be 3 patches: > >> 1. Change __mmc_switch > >> 2. Change HS200 and HS400 selection > >> 3. Change HS selection > >> > >> However there is another problem: card_busy is not the same as busy signal - > >> see below. So that needs to be sorted out first. > >> > > We should make that card_busy() is the same with busy signal asserted. > > as you know, if card was not in busy state, all data pins should be high > > level as it is pull-up by default. so that's no conflict to check card > > busy signal by DAT0 or DAT0 ~ DAT3. > > Potentially SDIO uses DAT1 for card interrupt, so that is a conflict right > there. > > Also SDHCI does it backwards (don't ask me why) and considers 0000 to be > busy, so there's another conflict. > > Some of the language in the SD and SDHCI specifications seems to indicate > that checking all 4 DAT lines during voltage switch is optional i.e. only 1 > of the lines must be checked. If that is true then we could change all the > drivers over to check just DAT0, and expect that to work for both busy > signalling and SD voltage switch checks. > > So it seems to me card_busy still needs to be sorted out first. One thing must point out is that the __mmc_switch() is only for MMC card. SD/SDIO will never use this interface. by the way, Per JEDEC SD3.0 spec, below is the quote from spec: "Completion of voltage switch sequence is checked by high level of DAT[3:0]. Any bit of DAT[3:0] can be checked depends on ability of the host." So that the implement of ops->card_busy() can be changed from check DAT[3:0] to only check DAT[0]. In fact, for SD/SDIO voltage switch, if switch success, all DAT pins are high level and if switch failed, all data pins are low level. > -- 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
