On Fri, Jul 6, 2018 at 10:36 AM, Lukas Wunner <lukas@xxxxxxxxx> wrote: > [cc += Kishon Vijay Abraham] > > On Thu, Jul 05, 2018 at 11:18:28AM +0200, Rafael J. Wysocki wrote: >> OK, so calling devices_kset_move_last() from really_probe() clearly is >> a mistake. >> >> I'm not really sure what the intention of it was as the changelog of >> commit 52cdbdd49853d doesn't really explain that (why would it be >> insufficient without that change?) > > It seems 52cdbdd49853d fixed an issue with boards which have an MMC > whose reset pin needs to be driven high on shutdown, lest the MMC > won't be found on the next boot. > > The boards' devicetrees use a kludge wherein the reset pin is modelled > as a regulator. The regulator is enabled when the MMC probes and > disabled on driver unbind and shutdown. As a result, the pin is driven > low on shutdown and the MMC is not found on the next boot. > > To fix this, another kludge was invented wherein the GPIO expander > driving the reset pin unconditionally drives all its pins high on > shutdown, see pcf857x_shutdown() in drivers/gpio/gpio-pcf857x.c > (commit adc284755055, "gpio: pcf857x: restore the initial line state > of all pcf lines"). > > For this kludge to work, the GPIO expander's ->shutdown hook needs to > be executed after the MMC expander's ->shutdown hook. > > Commit 52cdbdd49853d achieved that by reordering devices_kset according > to the probe order. Apparently the MMC probes after the GPIO expander, > possibly because it returns -EPROBE_DEFER if the vmmc regulator isn't > available yet, see mmc_regulator_get_supply(). > > Note, I'm just piecing the information together from git history, > I'm not responsible for these kludges. (I'm innocent!) Sure enough. :-) In any case, calling devices_kset_move_last() in really_probe() is plain broken and if its only purpose was to address a single, arguably kludgy, use case, let's just get rid of it in the first place IMO. > @Pingfan Liu, if you just remove the call to devices_kset_move_last() > from really_probe(), does the issue go away? I would think so from the description of the problem (elsewhere in this thread). Thanks, Rafael
