>From ac594ad4aff30af6d65375df1a5e6c3b43134721 Mon Sep 17 00:00:00 2001 From: John Bonesio <bones@xxxxxxxxxxxx> Date: Tue, 21 Jul 2009 13:15:40 -0700 Subject: [PATCH] ASoC: MPC5200: Increase the delay time between resets Reset was failing with the original udelay(50) between the code in psc_ac97_cold_reset() and the call to psc_ac97_warm_reset(). Through testing it was found that a delay of 1ms was necessary for the cold_reset code to consistently complete successfully. Signed-off-by: John Bonesio <bones@xxxxxxxxxxxx> --- sound/soc/fsl/mpc5200_psc_ac97.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/sound/soc/fsl/mpc5200_psc_ac97.c b/sound/soc/fsl/mpc5200_psc_ac97.c index 7eb5499..c4ae3e0 100644 --- a/sound/soc/fsl/mpc5200_psc_ac97.c +++ b/sound/soc/fsl/mpc5200_psc_ac97.c @@ -12,6 +12,7 @@ #include <linux/module.h> #include <linux/of_device.h> #include <linux/of_platform.h> +#include <linux/delay.h> #include <sound/pcm.h> #include <sound/pcm_params.h> @@ -112,7 +113,7 @@ static void psc_ac97_cold_reset(struct snd_ac97 *ac97) out_8(®s->op1, MPC52xx_PSC_OP_RES); udelay(10); out_8(®s->op0, MPC52xx_PSC_OP_RES); - udelay(50); + msleep(1); psc_ac97_warm_reset(ac97); } -- 1.6.0.4 On Tue, 2009-07-21 at 10:01 +0100, Mark Brown wrote: > On Mon, Jul 20, 2009 at 04:29:11PM -0700, John Bonesio wrote: > > > AC97 link. The AC97 driver also calls warm_reset() after the cold reset > > is complete. Earlier the warm_reset() call was added in the AC97 > > cold_reset() routine to attempt to solve this bug, but it appears to not > > completely solve the issue. After the reset the wm9712 driver attempts > > No, the warm reset is an unrelated change. The warm reset is there > because the WM9712 can be strapped to not start up the AC97 link at > startup. > > > 2. Perhaps the cold_reset is not necessary and the warm_reset is all > > that is needed > > No, AC97 cold and warm resets do different things. A cold reset > restores the device to power on state while a warm reset will restart > the AC97 link if it was not already running without changing any > register settings in the device. A warm reset cannot substitute for a > cold reset. > > [Buggy GPIOs] > > might contain uninitialized values on power up. Should I still consider > > this as a potential problem, or is this pretty much a non-issue? > > Depends how much you trust your AC97 controller. > > > would go away. So instead I increased the length of time in the udelay() > > call right before the call to warm_reset(). I've empirically found that > > delaying 1ms (udelay(50) -> udelay(1000)) seems to avoid the problem. > > I'm not sure why this delay is necessary, or if it makes sense for the > > hardware to need this much time to come out of the cold reset. > > I'm not sure which delay you're talking about here (I'm guessing that > it's one of those in the PSC driver?) but this does sound entirely > plausible - if it resolves the issue could you produce a patch, please? > I'd suggest changing to use msleep() instead of udeley() since delay > will busy wait while sleep won't. > > Thanks for your work on this. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
