Hi Uffe, Could you please explain about the way to add a time suitable for my case? On Mon, Oct 5, 2015 at 4:26 PM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: > On 24 September 2015 at 14:21, Muni Sekhar <munisekharrms@xxxxxxxxx> wrote: >> 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? > > I guess this is related to a regulator ramp up time somehow. > I would advise you to model this IO voltage through a regulator and > thus you can take care of the ramp up time within the regulator > implementation. If that's not possible, we need a way to add a time > suitable for your case. > > Kind regards > Uffe -- 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
