• Mike Dunn's avatar
    ALSA: pxa27x: fix ac97 warm reset · 3b4bc7bc
    Mike Dunn authored
    This patch fixes some code that implements a work-around to a hardware bug in
    the ac97 controller on the pxa27x.  A bug in the controller's warm reset
    functionality requires that the mfp used by the controller as the AC97_nRESET
    line be temporarily reconfigured as a generic output gpio (AF0) and manually
    held high for the duration of the warm reset cycle.  This is what was done in
    the original code, but it was broken long ago by commit fb1bf8cd
        ([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset())
    which changed the mfp to a GPIO input instead of a high output.
    
    The fix requires the ac97 controller to obtain the gpio via gpio_request_one(),
    with arguments that configure the gpio as an output initially driven high.
    
    Tested on a palm treo 680 machine.  Reportedly, this broken code only prevents a
    warm reset on hardware that lacks a pull-up on the line, which appears to be the
    case for me.
    Signed-off-by: default avatarMike Dunn <mikedunn@newsguy.com>
    Signed-off-by: default avatarIgor Grinberg <grinberg@compulab.co.il>
    Signed-off-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
    Cc: stable@vger.kernel.org
    3b4bc7bc
mfp-pxa27x.h 21.4 KB