From patchwork Tue Aug 31 07:14:56 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Billy Tsai X-Patchwork-Id: 12466587 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C600BC432BE for ; Tue, 31 Aug 2021 07:14:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9E1A61008 for ; Tue, 31 Aug 2021 07:14:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239338AbhHaHPl (ORCPT ); Tue, 31 Aug 2021 03:15:41 -0400 Received: from twspam01.aspeedtech.com ([211.20.114.71]:54503 "EHLO twspam01.aspeedtech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239265AbhHaHPk (ORCPT ); Tue, 31 Aug 2021 03:15:40 -0400 Received: from mail.aspeedtech.com ([192.168.0.24]) by twspam01.aspeedtech.com with ESMTP id 17V6sd4O028281; Tue, 31 Aug 2021 14:54:39 +0800 (GMT-8) (envelope-from billy_tsai@aspeedtech.com) Received: from BillyTsai-pc.aspeed.com (192.168.2.149) by TWMBX02.aspeed.com (192.168.0.24) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 31 Aug 2021 15:13:36 +0800 From: Billy Tsai To: , , , , , , , , , , , , , CC: Subject: [v5 13/15] iio: adc: aspeed: Add compensation phase. Date: Tue, 31 Aug 2021 15:14:56 +0800 Message-ID: <20210831071458.2334-14-billy_tsai@aspeedtech.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210831071458.2334-1-billy_tsai@aspeedtech.com> References: <20210831071458.2334-1-billy_tsai@aspeedtech.com> MIME-Version: 1.0 X-Originating-IP: [192.168.2.149] X-ClientProxiedBy: TWMBX02.aspeed.com (192.168.0.24) To TWMBX02.aspeed.com (192.168.0.24) X-DNSRBL: X-MAIL: twspam01.aspeedtech.com 17V6sd4O028281 Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org This patch adds a compensation phase to improve the accuracy of ADC measurement. This is the built-in function through input half of the reference voltage to get the ADC offset. Signed-off-by: Billy Tsai --- drivers/iio/adc/aspeed_adc.c | 54 +++++++++++++++++++++++++++++++++++- 1 file changed, 53 insertions(+), 1 deletion(-) diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c index 1333d7a88427..121c96de03bd 100644 --- a/drivers/iio/adc/aspeed_adc.c +++ b/drivers/iio/adc/aspeed_adc.c @@ -103,6 +103,7 @@ struct aspeed_adc_data { struct reset_control *rst; int vref_mv; u32 sample_period_ns; + int cv; }; #define ASPEED_CHAN(_idx, _data_reg_addr) { \ @@ -112,7 +113,8 @@ struct aspeed_adc_data { .address = (_data_reg_addr), \ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \ - BIT(IIO_CHAN_INFO_SAMP_FREQ), \ + BIT(IIO_CHAN_INFO_SAMP_FREQ) | \ + BIT(IIO_CHAN_INFO_OFFSET), \ } static const struct iio_chan_spec aspeed_adc_iio_channels[] = { @@ -134,6 +136,51 @@ static const struct iio_chan_spec aspeed_adc_iio_channels[] = { ASPEED_CHAN(15, 0x2E), }; +static int aspeed_adc_compensation(struct iio_dev *indio_dev) +{ + struct aspeed_adc_data *data = iio_priv(indio_dev); + u32 index, adc_raw = 0; + u32 adc_engine_control_reg_val; + + adc_engine_control_reg_val = + readl(data->base + ASPEED_REG_ENGINE_CONTROL); + adc_engine_control_reg_val &= ~ASPEED_ADC_OP_MODE; + adc_engine_control_reg_val |= + (FIELD_PREP(ASPEED_ADC_OP_MODE, ASPEED_ADC_OP_MODE_NORMAL) | + ASPEED_ADC_ENGINE_ENABLE); + /* + * Enable compensating sensing: + * After that, the input voltage of ADC will force to half of the reference + * voltage. So the expected reading raw data will become half of the max + * value. We can get compensating value = 0x200 - ADC read raw value. + * It is recommended to average at least 10 samples to get a final CV. + */ + writel(adc_engine_control_reg_val | ASPEED_ADC_CTRL_COMPENSATION | + ASPEED_ADC_CTRL_CHANNEL_ENABLE(0), + data->base + ASPEED_REG_ENGINE_CONTROL); + /* + * After enable compensating sensing mode need to wait some time for ADC stable + * Experiment result is 1ms. + */ + mdelay(1); + + for (index = 0; index < 16; index++) { + /* + * Waiting for the sampling period ensures that the value acquired + * is fresh each time. + */ + ndelay(data->sample_period_ns); + adc_raw += readw(data->base + aspeed_adc_iio_channels[0].address); + } + adc_raw >>= 4; + data->cv = BIT(ASPEED_RESOLUTION_BITS - 1) - adc_raw; + writel(adc_engine_control_reg_val, + data->base + ASPEED_REG_ENGINE_CONTROL); + dev_dbg(data->dev, "Compensating value = %d\n", data->cv); + + return 0; +} + static int aspeed_adc_set_sampling_rate(struct iio_dev *indio_dev, u32 rate) { struct aspeed_adc_data *data = iio_priv(indio_dev); @@ -163,6 +210,10 @@ static int aspeed_adc_read_raw(struct iio_dev *indio_dev, *val = readw(data->base + chan->address); return IIO_VAL_INT; + case IIO_CHAN_INFO_OFFSET: + *val = data->cv; + return IIO_VAL_INT; + case IIO_CHAN_INFO_SCALE: *val = data->vref_mv; *val2 = ASPEED_RESOLUTION_BITS; @@ -466,6 +517,7 @@ static int aspeed_adc_probe(struct platform_device *pdev) return ret; } + aspeed_adc_compensation(indio_dev); /* Start all channels in normal mode. */ adc_engine_control_reg_val = readl(data->base + ASPEED_REG_ENGINE_CONTROL);