Hello Marek, On Thu, Jan 29, 2015 at 10:15 AM, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: >> Also, I wonder whether we could extend the mmc-pwrseq to cover your >> case? Did you consider that as an option? > > > I didn't consider mmc-pwrseq yet. For me it looked straightforward to I agree with Ulf that using mmc-pwrseq would be a good solution and in fact I think the pwrseq_simple [0] driver will fit your use case since it supports a reset GPIO pin which is what many WLAN chips attached to a SDIO interface use. > implement > it just like card detect or write-protection gpio pins. I already noticed > that > there is code for some mmc host driver, which perform mmc hardware reset. If > you > think that extending pwrseq is the better approach, I will try to update my > patches. This will add reboot handler to mmc-pwrseq then. The only question > is I don't think that adding a reboot handler to mmc-pwrseq is needed. AFAICT the call chain is: sys_reboot() -> kernel_restart() -> device_shutdown() -> mmc_bus_shutdown() -> _mmc_suspend() -> mmc_power_off() -> mmc_pwrseq_power_off() -> struct mmc_pwrseq_ops .power_off So since the pwrseq_simple already asserts the reset GPIO in .power_off, it should be enough to ensure the eMMC will be reset to its default configuration for the iROM to work properly. It also asserts the GPIO pin in .pre_power_on and de-asserts in .post_power_on which should be needed as well for the other case you mentioned when a broken bootloader left the emmc card in some unknown state. > weather to use it always when mmc-pwrseq has been enabled or only if some > additional property like 'reset-on-reboot' has been provided. > Having a reset GPIO is optional AFAIK so I don't think there is a need for an additional "reset-on-reboot" propery. > Best regards > -- > Marek Szyprowski, PhD > Samsung R&D Institute Poland > Best regards, Javier [0]: FYI, these are the relevant commits in linux-next: fe1922d5d4d0 mmc: pwrseq_simple: Add support for a reset GPIO pin ec2017f2491f mmc: pwrseq: Initial support for the simple MMC power sequence provider fe1686658f9c mmc: pwrseq: Document DT bindings for the simple MMC power sequence 1b745e8a4627 mmc: core: Initial support for MMC power sequences -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
