• Grygorii Strashko's avatar
    driver core: correct device's shutdown order · 52cdbdd4
    Grygorii Strashko authored
    Now device's shutdown sequence is performed in reverse order of their
    registration in devices_kset list and this sequence corresponds to the
    reverse device's creation order. So, devices_kset data tracks
    "parent<-child" device's dependencies only.
    
    Unfortunately, that's not enough and causes problems in case of
    implementing board's specific shutdown procedures. For example [1]:
    "DRA7XX_evm uses PCF8575 and one of the PCF output lines feeds to
    MMC/SD and this line should be driven high in order for the MMC/SD to
    be detected. This line is modelled as regulator and the hsmmc driver
    takes care of enabling and disabling it. In the case of 'reboot',
    during shutdown path as part of it's cleanup process the hsmmc driver
    disables this regulator. This makes MMC boot not functional."
    
    To handle this issue the .shutdown() callback could be implemented
    for PCF8575 device where corresponding GPIO pins will be configured to
    states, required for correct warm/cold reset. This can be achieved
    only when all .shutdown() callbacks have been called already for all
    PCF8575's consumers. But devices_kset is not filled correctly now:
    
    devices_kset: Device61 4e000000.dmm
    devices_kset: Device62 48070000.i2c
    devices_kset: Device63 48072000.i2c
    devices_kset: Device64 48060000.i2c
    devices_kset: Device65 4809c000.mmc
    ...
    devices_kset: Device102 fixedregulator-sd
    ...
    devices_kset: Device181 0-0020 // PCF8575
    devices_kset: Device182 gpiochip496
    devices_kset: Device183 0-0021 // PCF8575
    devices_kset: Device184 gpiochip480
    
    As can be seen from above .shutdown() callback for PCF8575 will be called
    before its consumers, which, in turn means, that any changes of PCF8575
    GPIO's pins will be or unsafe or overwritten later by GPIO's consumers.
    The problem can be solved if devices_kset list will be filled not only
    according device creation order, but also according device's probing
    order to track "supplier<-consumer" dependencies also.
    
    Hence, as a fix, lets add devices_kset_move_last(),
    devices_kset_move_before(), devices_kset_move_after() and call them
    from device_move() and also add call of devices_kset_move_last() in
    really_probe(). After this change all entries in devices_kset will
    be sorted according to device's creation ("parent<-child") and
    probing ("supplier<-consumer") order.
    
    devices_kset after:
    devices_kset: Device121 48070000.i2c
    devices_kset: Device122 i2c-0
    ...
    devices_kset: Device147 regulator.24
    devices_kset: Device148 0-0020
    devices_kset: Device149 gpiochip496
    devices_kset: Device150 0-0021
    devices_kset: Device151 gpiochip480
    devices_kset: Device152 0-0019
    ...
    devices_kset: Device372 fixedregulator-sd
    devices_kset: Device373 regulator.29
    devices_kset: Device374 4809c000.mmc
    devices_kset: Device375 mmc0
    
    [1] http://www.spinics.net/lists/linux-mmc/msg29825.html
    
    Cc: Sekhar Nori <nsekhar@ti.com>
    Signed-off-by: default avatarGrygorii Strashko <grygorii.strashko@ti.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    52cdbdd4
dd.c 19.9 KB