From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755132AbdL1SH2 (ORCPT ); Thu, 28 Dec 2017 13:07:28 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:59076 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754177AbdL1RNY (ORCPT ); Thu, 28 Dec 2017 12:13:24 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Mark Brown" , "Ricard Wanderlof" , "Ricard Wanderlof" Date: Thu, 28 Dec 2017 17:05:44 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 002/204] ASoC: adau17x1: Workaround for noise bug in ADC In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Ricard Wanderlof commit 1e6f4fc06f6411adf98bbbe7fcd79442cd2b2a75 upstream. The ADC in the ADAU1361 (and possibly other Analog Devices codecs) exhibits a cyclic variation in the noise floor (in our test setup between -87 and -93 dB), a new value being attained within this range whenever a new capture stream is started. The cycle repeats after about 10 or 11 restarts. The workaround recommended by the manufacturer is to toggle the ADOSR bit in the Converter Control 0 register each time a new capture stream is started. I have verified that the patch fixes this problem on the ADAU1361, and according to the manufacturer toggling the bit in question in this manner will at least have no detrimental effect on other chips served by this driver. Signed-off-by: Ricard Wanderlof Signed-off-by: Mark Brown Signed-off-by: Ben Hutchings --- sound/soc/codecs/adau17x1.c | 24 +++++++++++++++++++++++- sound/soc/codecs/adau17x1.h | 2 ++ 2 files changed, 25 insertions(+), 1 deletion(-) --- a/sound/soc/codecs/adau17x1.c +++ b/sound/soc/codecs/adau17x1.c @@ -88,6 +88,27 @@ static int adau17x1_pll_event(struct snd return 0; } +static int adau17x1_adc_fixup(struct snd_soc_dapm_widget *w, + struct snd_kcontrol *kcontrol, int event) +{ + struct snd_soc_codec *codec = snd_soc_dapm_to_codec(w->dapm); + struct adau *adau = snd_soc_codec_get_drvdata(codec); + + /* + * If we are capturing, toggle the ADOSR bit in Converter Control 0 to + * avoid losing SNR (workaround from ADI). This must be done after + * the ADC(s) have been enabled. According to the data sheet, it is + * normally illegal to set this bit when the sampling rate is 96 kHz, + * but according to ADI it is acceptable for this workaround. + */ + regmap_update_bits(adau->regmap, ADAU17X1_CONVERTER0, + ADAU17X1_CONVERTER0_ADOSR, ADAU17X1_CONVERTER0_ADOSR); + regmap_update_bits(adau->regmap, ADAU17X1_CONVERTER0, + ADAU17X1_CONVERTER0_ADOSR, 0); + + return 0; +} + static const char * const adau17x1_mono_stereo_text[] = { "Stereo", "Mono Left Channel (L+R)", @@ -119,7 +140,8 @@ static const struct snd_soc_dapm_widget SND_SOC_DAPM_MUX("Right DAC Mode Mux", SND_SOC_NOPM, 0, 0, &adau17x1_dac_mode_mux), - SND_SOC_DAPM_ADC("Left Decimator", NULL, ADAU17X1_ADC_CONTROL, 0, 0), + SND_SOC_DAPM_ADC_E("Left Decimator", NULL, ADAU17X1_ADC_CONTROL, 0, 0, + adau17x1_adc_fixup, SND_SOC_DAPM_POST_PMU), SND_SOC_DAPM_ADC("Right Decimator", NULL, ADAU17X1_ADC_CONTROL, 1, 0), SND_SOC_DAPM_DAC("Left DAC", NULL, ADAU17X1_DAC_CONTROL0, 0, 0), SND_SOC_DAPM_DAC("Right DAC", NULL, ADAU17X1_DAC_CONTROL0, 1, 0), --- a/sound/soc/codecs/adau17x1.h +++ b/sound/soc/codecs/adau17x1.h @@ -120,5 +120,7 @@ bool adau17x1_has_dsp(struct adau *adau) #define ADAU17X1_CONVERTER0_CONVSR_MASK 0x7 +#define ADAU17X1_CONVERTER0_ADOSR BIT(3) + #endif