On 11 April 2017 at 10:17, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > On Tue, Apr 11, 2017 at 9:31 AM, Richard Leitner > <richard.leitner@xxxxxxxxxxx> wrote: > >> Some eMMCs disable their hardware reset line (RST_N) by default. To enable >> it the host must set the corresponding bit in ECSD. An example for such >> a device is the Micron MTFCxGACAANA-4M. >> >> This patch adds a new mmc-card devicetree property to let the host enable >> this feature during card initialization. >> >> Signed-off-by: Richard Leitner <richard.leitner@xxxxxxxxxxx> > > Do we know *WHY* these cards disable their hardware reset lines? Allow me to make a guess. In case the reset isn't enabled, the internal eMMC card firmware don't monitor the pin for the reset. I guess that could makes sense if SoC vendors has failed to properly connect the pin, avoiding the eMMC card to be reset when it shouldn't. > > If it is just some random over-cautious panic thing we might consider > just force re-enableing it, maybe with a warning in the dmesg, so we can > always reset the card. No DT property needed. There is actually already a DT property "cap-mmc-hw-reset" (MMC_CAP_HW_RESET), which tells whether the eMMC reset is supported by the host. Perhaps we can consider to force-enabling it for the eMMC card, when this property is set for the mmc host!? At least, inventing yet another binding doesn't make sense to me. > > Putting some people who work for eMMC vendors in the To: line so they > can say if they know about this. Yes, let's see what they say about it. > > Yours, > Linus Walleij Kind regards Uffe -- 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
