From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B331DC32774 for ; Tue, 23 Aug 2022 12:33:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241824AbiHWMdT (ORCPT ); Tue, 23 Aug 2022 08:33:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348860AbiHWMbf (ORCPT ); Tue, 23 Aug 2022 08:31:35 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64FA1101D04 for ; Tue, 23 Aug 2022 02:45:47 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 09CA7B81CA0 for ; Tue, 23 Aug 2022 09:44:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62584C433D6; Tue, 23 Aug 2022 09:44:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661247864; bh=6kd0s8jjXvZ1q9PVaDxVrTGPdQ1f6UvkAm1vFhO5Rw8=; h=Subject:To:From:Date:From; b=GhMf0YIAs6yoy/sQxamnw6vXZ5aAq7H0y3X/zBZNXClj0quQfjbsShmR6n9I1gOH5 8xrsPidq2fb4iWbOj+fLPjhGH8VhNmfMj57bxFWioEMJ+/RbbNgdCGEdZGBX+aQ6nf AeTnnTnvOsZYhRZUUMfsTCrQPxNPsBIOL1s5ri0k= Subject: patch "iio: adc: mcp3911: use correct formula for AD conversion" added to char-misc-linus To: marcus.folkesson@gmail.com, Jonathan.Cameron@huawei.com, Stable@vger.kernel.org, andy.shevchenko@gmail.com From: Date: Tue, 23 Aug 2022 10:42:58 +0200 Message-ID: <166124417857138@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This is a note to let you know that I've just added the patch titled iio: adc: mcp3911: use correct formula for AD conversion to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >From 9e2238e3ae40d371a1130226e0e740aa1601efa6 Mon Sep 17 00:00:00 2001 From: Marcus Folkesson Date: Fri, 22 Jul 2022 15:07:20 +0200 Subject: iio: adc: mcp3911: use correct formula for AD conversion The ADC conversion is actually not rail-to-rail but with a factor 1.5. Make use of this factor when calculating actual voltage. Fixes: 3a89b289df5d ("iio: adc: add support for mcp3911") Signed-off-by: Marcus Folkesson Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20220722130726.7627-4-marcus.folkesson@gmail.com Cc: Signed-off-by: Jonathan Cameron --- drivers/iio/adc/mcp3911.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c index f8875076ae80..890af7dca62d 100644 --- a/drivers/iio/adc/mcp3911.c +++ b/drivers/iio/adc/mcp3911.c @@ -40,8 +40,8 @@ #define MCP3911_CHANNEL(x) (MCP3911_REG_CHANNEL0 + x * 3) #define MCP3911_OFFCAL(x) (MCP3911_REG_OFFCAL_CH0 + x * 6) -/* Internal voltage reference in uV */ -#define MCP3911_INT_VREF_UV 1200000 +/* Internal voltage reference in mV */ +#define MCP3911_INT_VREF_MV 1200 #define MCP3911_REG_READ(reg, id) ((((reg) << 1) | ((id) << 5) | (1 << 0)) & 0xff) #define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff) @@ -139,11 +139,18 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev, *val = ret / 1000; } else { - *val = MCP3911_INT_VREF_UV; + *val = MCP3911_INT_VREF_MV; } - *val2 = 24; - ret = IIO_VAL_FRACTIONAL_LOG2; + /* + * For 24bit Conversion + * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5 + * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5) + */ + + /* val2 = (2^23 * 1.5) */ + *val2 = 12582912; + ret = IIO_VAL_FRACTIONAL; break; } -- 2.37.2