Hi MMC team, I've spent some time trying to add a regulator to control power to an SD card (vmmc-supply) on an SDHCI-equipped system. After a few false starts and red herrings I found that powering up the regulator during the boot process was effectively disabling the SDHCI controller. Note that this was despite having regulator-boot-on set in the device tree. The problem seems to be in sdhci_set_power_reg: mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, vdd); if (mode != MMC_POWER_OFF) sdhci_writeb(host, SDHCI_POWER_ON, SDHCI_POWER_CONTROL); else sdhci_writeb(host, 0, SDHCI_POWER_CONTROL); This looks plausible for the MMC_POWER_OFF case, but setting the SDHCI_POWER_CONTROL register to SDHCI_POWER_ON (0x01) has the side effect of settings the SD Bus Voltage Select bits to 0b000 (a reserved value). sdhci_set_power_noreg() includes logic to calculate the correct values for the voltage select bits, so I found that (in my limited test cases) replacing the if/else above with a chain call to sdhci_set_power_noreg() was sufficient to get everything working. Can anyone tell me what I've been doing wrong, or suggest a better "fix"? Thanks for your time, Phil Elwell
