mmc: core: Prevent violation of specs while initializing cards
According to eMMC/SD/SDIO specs, the VDD (VCC) voltage level must be maintained during the initialization sequence. If we want/need to tune the voltage level, a complete power cycle of the card must be executed. Most host drivers conforms to the specifications by only allowing to change VDD voltage level at the MMC_POWER_UP state, but some also cares about MMC_POWER_ON state, which they should'nt. This patch will not break those drivers, but they could clean up code to better reflect what is expected from the protocol layer. A big re-work of the mmc_select_voltage function is done to only change VDD voltage level if the host supports MMC_CAP2_FULL_PWR_CYCLE. Otherwise only validation of the host and card ocr mask will be done. A very nice side-effect of this patch is that we now don't need to reset the negotiated ocr mask at the mmc_power_off function, since now it will actually reflect the present voltage level, which safely can be used at the next power up and re-initialization. Moreover, we then only need to execute mmc_select_voltage from the attach sequence. Signed-off-by:Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: