mmc: sdhci: Make signal voltage support explicit
Signal voltage support is not a quirk, it is a capability. According to the SDHCI specification, support for 1.8V signaling is determined by the presence of one of the capability bits SDHCI_SUPPORT_SDR50, SDHCI_SUPPORT_SDR104, or SDHCI_SUPPORT_DDR50. This is complicated by also supporting eMMC which has 1.8V modes and 1.2V modes. It would be possible to use the transfer mode to determine signal voltage support, except for eMMC DDR52 mode which uses the same capability (MMC_CAP_1_8V_DDR) for 1.8V signaling and 3V signaling. In addition, the mmc core will fail over from one signaling voltage to the next (refer mmc_power_up()) which means SDHCI really needs to validate which voltages are actually supported. Introduce SDHCI flags for signal voltage support and set them based on the supported transfer modes. In general, drivers should prefer to set the supported transfer modes correctly rather than change the signal voltage capability, except in the case where 3V DDR52 is supported but 1.8V is not. Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com> Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
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