On 30 January 2015 at 11:37, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: > Hello, > > On 2015-01-29 11:56, Javier Martinez Canillas wrote: >> >> 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. > > > Ok, I've checked mmc-prwseq and mmc-pwrseq-simple. I also checked the > hardware and it mmc-pwrseq-simple cannot be used directly. > > Although the signal is called RSTN (on Odroid U3 schema), the eMMC card > gets resetted not on low line level, but during the rising edge. This RSTN > line is also pulled up by the external resistor. However, the strangest > thing is the fact that the default SoC configuration (which is applied > during hw reset) for this GPIO line is input, pulled-down. The SoC > internal pull-down is stronger than the external pull up, so in the end, > during the SoC reboot the RSTN signal is set to zero. Later bootloader > disables the internal pull-down. > > To sum up - to perform proper reboot on Odroid U3/XU3, one need to set > RSTN to zero, wait a while and the set it back to 1. > > To achieve this with mmc-pwrseq-simple, I would need to modify the power_off > callback to toggle reset line to zero and back to one. This however might > not be desired to other sd/mmc cards used with mmc-pwrseq-simple. > > I can also provide separate mmc-pwrsrq-odroid driver, which will be very > similar to mmc-pwrseq-simple. > > Ulf - which approach would you prefer? To me this seems like a quite generic eMMC hw-reset thing, thus we should maybe add a new pwrseq "driver" for it. In principle you need to toogle a GPIO in the ->pre_power_on() callback, right? And you are also proposing to register a restart handler from the ->alloc() callback!? I suppose this should work nicely. Kind regards Uffe > > >> >>> 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. > > > emergency_restart() doesn't call device_shutdown(), so I think it still > makes > sense to add real reset handler to mmc-pwrseq to ensure that power_off will > be called even during emergency_restart(). > > > Best regards > -- > Marek Szyprowski, PhD > Samsung R&D Institute Poland > -- 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
