Hi Doug, [snip] >>>> I think you shall be able use MMC_CAP_NEEDS_POLL, to handle this >>>> broken card detect mechanism. We even have a DT binding for that, >>>> "broken-cd". >>> >>> I don't think this is possible, but let me explain why I think so and >>> you can correct me. >>> >>> The voltage domain of the "card detect" pin on the SoC is vqmmc, >>> right? That means that you won't be able to read the pin without >>> turning on vqmmc. Even if you could read the pin without turning on >>> vqmmc, the pullup on this line is connected to vqmmc too. ...so if >>> vqmmc is off then there's no pulup and you can't use card detect. >>> >>> Are you suggesting that we should flip the voltage of vqmmc (and thus >>> vmmc to prevent damaging the card) during polling? That seems ugly. >> >> I am not sure I follow to understand the problem. All I am saying is: >> From your ->set_ios() when you get MMC_POWER_UP, enable vcc and vccq. >> From your ->set_ios() when you get MMC_POWER_OFF, disable vccq and vcc. >> >> The rest is taken care of from mmc core, when trying to initialize the card. > > We must not be on the same page, so I'll put all my assumptions in > super detail and we can see what's different... > > > So if I have "MMC_CAP_NEEDS_POLL" set, the MMC core will poll things, > right? ...and you are suggesting that I could solve my vqmmc vs. card > detect problem by using MMC_CAP_NEEDS_POLL, right? Yes. > > > Let's think about the case when no card is inserted. When no card is > inserted the core will call set_ios() with MMC_POWER_OFF, right? > > ...and we want that to turn off vmmc. > ...and if we turn off vmmc, we should turn off vqmmc. Correct. At MMC_POWER_OFF, all host drivers shall turn off all the possible powers that goes to the card. I am just telling this to make sure, we don't think this is a dw_mmc specific thing. > > Now we've got vmmc off and vqmmc off and on this board we can't read > the card detect line, right? Got it. :-) > > Now, we've got MMC_CAP_NEEDS_POLL, so dw_mmc will periodically be > called to check the card detect line, but with vmmc and vqmmc off. It > will be unable to return a sensible value without actually turning on > vmmc and vqmmc. Currently MMC_CAP_NEEDS_POLL mean the mmc rescan work will reschedule itself with HZ interval. This to check for card insert/removal. Now, mmc_rescan() will, if present, invoke host's ->get_cd() callback to check whether it's worth to continue initialization sequence or if it should re-schedule itself again. If your host driver can distinguish whether a card is inserted, which in this the are when vccq is turned off, your ->get_cd() callback need to return 0. That will allow mmc_rescan() to continue it's initialization sequence and do mmc_power_up(). > > > ...so with that context, I'll ask my questoin again: > > Are you suggesting that we should flip the voltage of vqmmc (and thus > vmmc to prevent damaging the card) during polling? That seems ugly. Nope. Kind regards Uffe -- 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
