Hi , We planned to use the standard Linux MMC driver for our FPGA based SD Host controller hardware. I am having couple of doubts regarding SDIO voltage change (sdhci_do_start_signal_voltage_switch()), please clarify me on this. The MMC driver sets and clears bit 3 of the HOST_CONTROL_2 register, when an IO voltage change is required (1=1.8v, 0=3.3v). Our hardware detects a change in this bit value, and generates a new interrupt when a change is seen. This interrupt will be controlled by some new registers, outside of the standard Host Controller register set. The interrupt handling routine shall, when seeing this interrupt, program the desired SDIO IO voltage change. MMC driver expects the voltage change to complete within 5ms - there is a fixed 5ms wait in the MMC driver’s sdhci_do_start_signal_voltage_switch() function. But our hardware is nowhere near capable of conducting a voltage change in 5ms. Instead it’s of the order of ~300ms. Does it causes any issues later during testing? If so what should be the best possible solution? -- Thanks, Sekhar -- 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
