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ALSA: pxa27x: fix ac97 warm reset

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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: Mike Dunn <mikedunn@newsguy.com>
Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Mike Dunn
2013-01-07 13:55:13 -08:00
committed by Mark Brown
parent 41b645c862
commit 3b4bc7bccc
3 changed files with 22 additions and 3 deletions
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4
arch/arm/mach-pxa/pxa27x.c
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@@ -47,9 +47,9 @@ void pxa27x_clear_otgph(void)
EXPORT_SYMBOL(pxa27x_clear_otgph);
static unsigned long ac97_reset_config[] = {
GPIO113_GPIO,
GPIO113_AC97_nRESET_GPIO_HIGH,
GPIO113_AC97_nRESET,
GPIO95_GPIO,
GPIO95_AC97_nRESET_GPIO_HIGH,
GPIO95_AC97_nRESET,
};