• Julius Werner's avatar
    vboot: Update block devices from VbExKeyboardRead() to fix SD detection · 6b4baa85
    Julius Werner authored
    The problem with SD cards is that you need to keep track of removals and
    reinsertions so that you know when you have to fully reinitialize it. In
    depthcharge, we do that by maintaining a 'present' member in the MMC
    controller object. On every update() call to the controller, we check if
    the previously known 'present' state still matches the current
    card_detect pin value, and if it doesn't we handle the respective
    insertion or removal.
    This works fine in recovery mode: vboot keeps checking for new media
    automatically every second, so we regularly call update() on all our
    removable block device controllers. But in dev mode, vboot only asks us
    to do that when it reads an explicit Ctrl+U from the user. This creates
    a problem when the user inserts an SD card with an invalid image,
    presses Ctrl+U (vboot sees that the image is invalid and beeps),
    replaces the SD card with a different one and presses Ctrl+U again. We
    only call update() twice on the block device controller in this case,
    and in both cases there is a card present. The driver has no chance to
    notice that it is no longer the same card and has to be reinitialized.
    It's hard to solve this in a good way: we could make it the
    responsibility of the individual MMC controller driver to track this
    (through some sort of controller-internal hardware latch), but it's
    unclear whether all controllers could support that, and it would have to
    be fixed in every single controller driver individually. We could also
    change the vboot API to add an explicit polling function that tells
    depthcharge to update this state, but that seems overkill at a time
    where we're thinking about moving away from depthcharge at some point
    anyway (towards a solution that probably wouldn't have this problem).
    This patch implements the quick and dirty fix of updating removable
    block device controllers in the only continuously polled vboot callback
    we have in dev mode, which is VbExKeyboardRead(). It's not exactly a
    clean solution from a design standpoint, but it'll work. USB storage
    devices essentially get the same treatment already because libpayload
    unconditionally calls usb_poll() as part of havechar()... so it's not
    really any worse than what we already have, just in a different place.
    TEST=Boot an Elm, plug in a uSD card without a good image, press Ctrl+U,
    replace SD card with one that has a good image, press Ctrl+U again,
    watch it boot.
    Change-Id: I729a37028140f354478422078804e750079a4c23
    Signed-off-by: default avatarJulius Werner <jwerner@chromium.org>
    Reviewed-on: https://chromium-review.googlesource.com/750321
    Reviewed-by: default avatarAaron Durbin <adurbin@chromium.org>
    Reviewed-by: default avatarFurquan Shaikh <furquan@chromium.org>