On Wed, Jan 11, 2017 at 2:55 PM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: > On 9 January 2017 at 05:53, Matt Ranostay <matt@ranostay.consulting> wrote: >> On Fri, Dec 30, 2016 at 12:05 AM, Linus Walleij >> <linus.walleij@xxxxxxxxxx> wrote: >>> On Mon, Dec 19, 2016 at 1:01 AM, Matt Ranostay <matt@ranostay.consulting> wrote: >>> >>>> * SD8787 has a "powerdown" line, and CW1200 has a "powerup" line.. I >>>> know this is a simple logic inversion. >>> >>> If this is a GPIO line, the GPIO subsystem can flag a line for >>> inverted logic. GPIO_ACTIVE_LOW from device tree for example. >> >> Slight ping on Ulf on this thread :). > > Thanks, sorry for the delay! > >> >> I do understand the inverted logic flag but that doesn't help if there >> are different logic states between various chipsets. > > For cw1200 (I looked at code from an old ST-Ericsson vendor tree), the > sequence is as follows: > > 1) Enable clock/power to the card/chip. > 2) Assert GPIO pin. I assume this also can be done before the > clock/power is enabled. > 3) Wait some time (~50ms). > 4) De-assert GPIO pin. > 5) Wait some time (~20ms) > 6) Assert GPIO pin. > 7) Wait some time (~32ms). > > At power off, the GPIO pin is de-asserted and of course also the > clock/power is disabled. Just to make sure we have all the relevant > logic. > > Looking at mmc pwrseq simple, perhaps we can extend this to deal with > GPIOs that needs to be *toggled*, as this is not just reset GPIOs. > Then we also need to deal with the delays in-between the toggling. Wouldn't we need to have a per chip function for each device supported? As well document gpios? I suspect we'd need an array of gpios defined in device tree since different devices will likely have various numbers of pins to toggle - Matt > > Thoughts? > > Kind regards > Uffe -- 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
