At Fri, 11 Mar 2011 11:24:52 +0100, Paul Bolle wrote:

At every resume a laptop I use prints this message (at KERN_ERR level): ALSA sound/pci/intel8x0m.c:904: AC'97 warm reset still in progress? [0x2]

The thing to note here is that 0x2 corresponds to ICH_AC97COLD. Ie, what seems to be happening is that the register involved indicated a warm reset for some time (as the ICH_AC97WARM bit was set) but by the time the warning is printed, and that same register is checked again, that bit is already cleared and only the ICH_AC97COLD bit is still set.

It turns out a warm reset needs some time to settle, but it is currently checked right away. The test therefore fails the first time it is done and schedule_timeout_uninterruptible() will be called. Once we return from that jiffies is already (far) past end_time on this laptop, so we exit the loop, print a warning, and exit the function while the warm reset actually succeeded.

A way to fix this is to call usleep_range() after writing to the register involved. A handful of tests suggest 500 usecs is a safe value. (This might punish the "finish cold reset" case, but on this laptop such a cold reset apparently never happens, so I can't say for sure.)

While we're at it drop the extra single tick from end_time, as it looks rather silly.

Signed-off-by: Paul Bolle pebolle@tiscali.nl

Applied now. Thanks.

Takashi

---

changes in v3:

• add comment
• use usleep_range()

sound/pci/intel8x0m.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/sound/pci/intel8x0m.c b/sound/pci/intel8x0m.c index 13cec1e..b1c926c 100644 --- a/sound/pci/intel8x0m.c +++ b/sound/pci/intel8x0m.c @@ -894,7 +894,8 @@ static int snd_intel8x0m_ich_chip_init(struct intel8x0m *chip, int probing) /* finish cold or do warm reset */ cnt |= (cnt & ICH_AC97COLD) == 0 ? ICH_AC97COLD : ICH_AC97WARM; iputdword(chip, ICHREG(GLOB_CNT), cnt);

• end_time = (jiffies + (HZ / 4)) + 1;

• usleep_range(500, 1000); /* give warm reset some time */
• end_time = jiffies + HZ / 4; do { if ((igetdword(chip, ICHREG(GLOB_CNT)) & ICH_AC97WARM) == 0) goto __ok;

-- 1.7.4.1