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 AFC7CC27C47 for ; Sat, 28 Oct 2023 15:35:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229519AbjJ1PfJ (ORCPT ); Sat, 28 Oct 2023 11:35:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229449AbjJ1PfG (ORCPT ); Sat, 28 Oct 2023 11:35:06 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0137FCF; Sat, 28 Oct 2023 08:35:03 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7EA43C433C7; Sat, 28 Oct 2023 15:34:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698507303; bh=qZnyFgLTqkYYWA+lM+ITN7Oli/7TuoF3B+RoNn5As90=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Kou2MhaOa2fZQVtIYAc3lLl0VADeS/ZrHI90OHbfUzbOpCkdlNNpozjEF/Cn07XQU hJ9h88GZ1NgpfJUi1wm2qmvOgWd8bWXhJIq7KHd4+XOgjDg8Jd/CH3X8VuzZjNYQ6U cVxk4ZEVRmrGW4CwZzRXUiT8SxqRNx+uKgjfEqNkqre2mtmQenbxSEOS2KXaqLSTQs YWqO8XxJQfFY8Wco5BgExcOcfU4k91T17ZTjN65AKF6BEC7t1mbNDlmBMKWtgE31J5 hvAJ8pHIkFkaZy94A37GEmMAvJhpjcGN+SvWOzUtL1k7ZJHLmnyXbrWO8U8lNS2wJB lHPZFK7PR78Og== Date: Sat, 28 Oct 2023 16:34:42 +0100 From: Jonathan Cameron To: Javier Carrasco Cc: Lars-Peter Clausen , William Markezana , Ludovic Tancerel , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] iio: common: ms_sensors: ms_sensors_i2c: fix humidity conversion time table Message-ID: <20231028163442.2b803993@jic23-huawei> In-Reply-To: <20231026-topic-htu21_conversion_time-v1-1-bd257dc44209@gmail.com> References: <20231026-topic-htu21_conversion_time-v1-1-bd257dc44209@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Thu, 26 Oct 2023 17:44:49 +0200 Javier Carrasco wrote: > The HTU21 offers 4 sampling frequencies: 20, 40, 70 and 120, which are > associated to an index that is used to select the right measurement > resolution and its corresponding measurement time. The current > implementation selects the measurement resolution and the temperature > measurement time properly, but it does not select the right humidity > measurement time in all cases. > > In summary, the 40 and 70 humidity measurement times are swapped. > > The reason for that is probably the unusual coding for the measurement > resolution. According to the datasheet, the bits [7,0] of the "user > register" are used as follows to select the bit resolution: > > -------------------------------------------------- > | Bit 7 | Bit 0 | RH | Temp | Trh (us) | Tt (us) | > -------------------------------------------------- > | 0 | 0 | 12 | 14 | 16000 | 50000 | > -------------------------------------------------- > | 0 | 1 | 8 | 12 | 3000 | 13000 | > -------------------------------------------------- > | 1 | 0 | 10 | 13 | 5000 | 25000 | > -------------------------------------------------- > | 1 | 1 | 11 | 11 | 8000 | 7000 | > -------------------------------------------------- > *This table is available in the official datasheet, page 13/21. I have > just appended the times provided in the humidity/temperature tables, > pages 3/21, 5/21. Note that always a pair of resolutions is selected. > > The sampling frequencies [20, 40, 70, 120] are assigned to a linear > index [0..3] which is then coded as follows [1]: > > Index [7,0] > -------------- > idx 0 0,0 > idx 1 1,0 > idx 2 0,1 > idx 3 1,1 > > That is done that way because the temperature measurements are being > used as the reference for the sampling frequency (the frequencies and > the temperature measurement times are correlated), so increasing the > index always reduces the temperature measurement time and its > resolution. Therefore, the temperature measurement time array is as > simple as [50000, 25000, 13000, 7000] > > On the other hand, the humidity resolution cannot follow the same > pattern because of the way it is coded in the "user register", where > both resolutions are selected at the same time. The humidity measurement > time array is the following: [16000, 3000, 5000, 8000], which defines > the following assignments: > > Index [7,0] Trh > ----------------------- > idx 0 0,0 16000 -> right, [0,0] selects 12 bits (Trh = 16000) > idx 1 1,0 3000 -> wrong! [1,0] selects 10 bits (Trh = 5000) > idx 2 0,1 5000 -> wrong! [0,1] selects 8 bits (Trh = 3000) > idx 3 1,1 8000 -> right, [1,1] selects 11 bits (Trh = 8000) > > The times have been ordered as if idx = 1 -> [0,1] and idx = 2 -> [1,0], > which is not the case for the reason explained above. > > So a simple modification is required to obtain the right humidity > measurement time array, swapping the values in the positions 1 and 2. > > The right table should be the following: [16000, 5000, 3000, 8000] > > Fix the humidity measurement time array with the right idex/value > coding. > > [1] The actual code that makes this coding and assigns it to the current > value of the "user register" is the following: > config_reg &= 0x7E; > config_reg |= ((i & 1) << 7) + ((i & 2) >> 1); > > Fixes: d574a87cc311 ("Add meas-spec sensors common part") > Signed-off-by: Javier Carrasco Good description. That's horrible :( Applied to the fixes-togreg branch of iio.git and marked for stable. Note however that I probably won't send a fixes pull request until after rc1 is out in about 3 weeks time. Thanks, Jonathan > --- > drivers/iio/common/ms_sensors/ms_sensors_i2c.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/iio/common/ms_sensors/ms_sensors_i2c.c b/drivers/iio/common/ms_sensors/ms_sensors_i2c.c > index 6633b35a94e6..9c9bc77003c7 100644 > --- a/drivers/iio/common/ms_sensors/ms_sensors_i2c.c > +++ b/drivers/iio/common/ms_sensors/ms_sensors_i2c.c > @@ -15,8 +15,8 @@ > /* Conversion times in us */ > static const u16 ms_sensors_ht_t_conversion_time[] = { 50000, 25000, > 13000, 7000 }; > -static const u16 ms_sensors_ht_h_conversion_time[] = { 16000, 3000, > - 5000, 8000 }; > +static const u16 ms_sensors_ht_h_conversion_time[] = { 16000, 5000, > + 3000, 8000 }; > static const u16 ms_sensors_tp_conversion_time[] = { 500, 1100, 2100, > 4100, 8220, 16440 }; > > > --- > base-commit: 611da07b89fdd53f140d7b33013f255bf0ed8f34 > change-id: 20231026-topic-htu21_conversion_time-9ea81e86703f > > Best regards,