From mboxrd@z Thu Jan 1 00:00:00 1970 From: Charles Keepax Subject: Re: [PATCH] ASoC: wm_hubs: Fix DC Servo readback Date: Wed, 13 Aug 2014 13:39:00 +0100 Message-ID: <20140813123900.GL15833@opensource.wolfsonmicro.com> References: <1407926840-8576-1-git-send-email-nikesh@opensource.wolfsonmicro.com> <20140813110844.GF15833@opensource.wolfsonmicro.com> <20140813113841.GP17528@sirena.org.uk> <20140813121637.GH15833@opensource.wolfsonmicro.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20140813121637.GH15833@opensource.wolfsonmicro.com> Sender: linux-kernel-owner@vger.kernel.org To: Mark Brown Cc: alsa-devel@alsa-project.org, tiwai@suse.de, patches@opensource.wolfsonmicro.com, lgirdwood@gmail.com, Nikesh Oswal , linux-kernel@vger.kernel.org, perex@perex.cz List-Id: alsa-devel@alsa-project.org On Wed, Aug 13, 2014 at 01:16:37PM +0100, Charles Keepax wrote: > On Wed, Aug 13, 2014 at 12:38:41PM +0100, Mark Brown wrote: > > On Wed, Aug 13, 2014 at 12:08:44PM +0100, Charles Keepax wrote: > > > On Wed, Aug 13, 2014 at 11:47:20AM +0100, Nikesh Oswal wrote: > > > > > > case 2: > > > > dcs_reg = WM8994_DC_SERVO_4E; > > > > break; > > > > - case 1: > > > > - dcs_reg = WM8994_DC_SERVO_READBACK; > > > > - break; > > > > default: > > > > dcs_reg = WM8993_DC_SERVO_3; > > > > break; > > > > > This doesn't look right, firstly if it is the same register for > > > all versions then surely we should change the code that sets > > > dcs_readback_mode rather than setting that to different values > > > but treating them the same. Although obviously if nothing still > > > uses this case we could remove it as well. > > > > > Also I think the situation is more complex for example on version > > > 4.4 of the datasheet for wm8994 the WR_VAL fields appear to be in > > > register 59h. Which is not consistent with this. > > > > There was a change in the DC servo between revisions of the WM8994 (at > > revision E from the look of the code). This isn't documented in the > > datasheets as they only document current silicon. > > Indeed, but this patch sets all revs of wm8994 to use register 57h. > The lastest version of the datasheet has this register at 59h > although some of the older versions of the datasheet (which likely > match some older revs of the chip although no way to tell which one > just from the datasheet) have it at 57h. > > I think basically we need to get some clarity from hardware here > on which revs use which address and update this patch to match, > but either way it looks likely that this patch doesn't address > the whole picture. Sorry no ignore me I am talking non-sense here. It still treats the newer revs correctly, I suspect this might be a nice change though: --- a/sound/soc/codecs/wm_hubs.c +++ b/sound/soc/codecs/wm_hubs.c @@ -209,7 +209,7 @@ static int wm_hubs_read_dc_servo(struct snd_soc_codec *codec, dcs_reg = WM8994_DC_SERVO_4E; break; case 1: - dcs_reg = WM8994_DC_SERVO_READBACK; + dcs_reg = WM8994_DC_SERVO_4; break; Thanks, Charles