From: Liam Girdwood <liam.girdwood@wolfsonmicro.com>
To: Jeff Garzik <jgarzik@pobox.com>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: [BUG] unsafe reset in ac97_codec.c
Date: Tue, 03 Feb 2004 15:42:28 +0000 [thread overview]
Message-ID: <1075822947.5204.506.camel@cearnarfon> (raw)
Hi
Does anyone know why ac97_codec.c does a register reset of the codec
during device probing. i.e.
/* probing AC97 codec, AC97 2.0 says that bit 15 of register 0x00
(reset) should
* be read zero.
*
* FIXME: is the following comment outdated? -jgarzik
* Probing of AC97 in this way is not reliable, it is not even SAFE !!
*/
codec->codec_write(codec, AC97_RESET, 0L);
IMO, this is unsafe because it can also reset the codec into it's
default power state which can be "power down". This is not normally a
problem for PC's, but some battery powered devices have the default
codec state as "power down" to conserve power.
Was this introduced as a workaround for some buggy device ?
If no one objects I'll submit a patch.
Liam
next reply other threads:[~2004-02-03 15:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-03 15:42 Liam Girdwood [this message]
2004-02-04 21:24 ` [BUG] unsafe reset in ac97_codec.c Jeff Garzik
2004-02-05 16:31 ` Liam Girdwood
2004-02-05 17:59 ` Alan Cox
2004-02-26 15:55 ` Liam Girdwood
2004-02-29 18:38 ` Jeff Garzik
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