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 X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 CF3C5C3F68F for ; Wed, 12 Feb 2020 14:03:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A462220724 for ; Wed, 12 Feb 2020 14:03:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=st.com header.i=@st.com header.b="ChsTacUV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728189AbgBLODH (ORCPT ); Wed, 12 Feb 2020 09:03:07 -0500 Received: from mx07-00178001.pphosted.com ([62.209.51.94]:1427 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725887AbgBLODG (ORCPT ); Wed, 12 Feb 2020 09:03:06 -0500 Received: from pps.filterd (m0046037.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 01CDwcg2007768; Wed, 12 Feb 2020 15:02:39 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=st.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=STMicroelectronics; bh=/8l92jgFtvZ9KFonos6IeWCOhSFNRaH+VFtBAk4RDCo=; b=ChsTacUV8Q4OByXultemNzXtr/cnMMHJ5reMiF4MGcikCkWxcnKUlVuoy6Y4MVbdKGbx t4i83krf+dl603BYsHPaErugW3dvhWq3ky4tFZ2WQM8D1tUoFhp1A77Ob2IoKFUmGdO4 vkBoLZc9dR93AKyH6kYU4kYlnWQf19PniZUn9xR5B5pE91j8iv7ZHafW+I+FSOkApOzf cOawaUAMuwgfk/+J2YDir6cFY3yUt0eLWxq5pxvuPfuXsdHDt11f/bAj8v0gdz/28iy7 Fe9TsClg15V3akbq2jDD3oEPeGvE6YnjlBa/pycuGSAmRc69v7Tez1IRnn0fEKItvVPA TA== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com with ESMTP id 2y1urhet63-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Feb 2020 15:02:39 +0100 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 62B8E10002A; Wed, 12 Feb 2020 15:02:38 +0100 (CET) Received: from Webmail-eu.st.com (sfhdag5node3.st.com [10.75.127.15]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 4D3452B46AE; Wed, 12 Feb 2020 15:02:38 +0100 (CET) Received: from [10.48.0.71] (10.75.127.45) by SFHDAG5NODE3.st.com (10.75.127.15) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 12 Feb 2020 15:02:37 +0100 Subject: Re: [PATCH] iio: adc: stm32-adc: fix runtime autosuspend delay when slow polling To: Jonathan Cameron , "Rafael J. Wysocki" CC: , , , , , , , , , , , , References: <1579854369-7972-1-git-send-email-fabrice.gasnier@st.com> <20200202153354.3dae5863@archlinux> From: Fabrice Gasnier Message-ID: Date: Wed, 12 Feb 2020 15:02:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200202153354.3dae5863@archlinux> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.45] X-ClientProxiedBy: SFHDAG6NODE2.st.com (10.75.127.17) To SFHDAG5NODE3.st.com (10.75.127.15) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-12_07:2020-02-11,2020-02-12 signatures=0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/2/20 4:33 PM, Jonathan Cameron wrote: > On Fri, 24 Jan 2020 09:26:09 +0100 > Fabrice Gasnier wrote: > >> When the ADC is runtime suspended and starting a conversion, the stm32-adc >> driver calls pm_runtime_get_sync() that gets cascaded to the parent >> (e.g. runtime resume of stm32-adc-core driver). This also kicks the >> autosuspend delay (e.g. 2s) of the parent. >> Once the ADC is active, calling pm_runtime_get_sync() again (upon a new >> capture) won't kick the autosuspend delay for the parent (stm32-adc-core >> driver) as already active. >> >> Currently, this makes the stm32-adc-core driver go in suspend state >> every 2s when doing slow polling. As an example, doing a capture, e.g. >> cat in_voltageY_raw at a 0.2s rate, the auto suspend delay for the parent >> isn't refreshed. Once it expires, the parent immediately falls into >> runtime suspended state, in between two captures, as soon as the child >> driver falls into runtime suspend state: >> - e.g. after 2s, + child calls pm_runtime_put_autosuspend() + 100ms >> autosuspend delay of the child. >> - stm32-adc-core switches off regulators, clocks and so on. >> - They get switched on back again 100ms later in this example (at 2.2s). >> >> So, add an explicit call to pm_runtime_mark_last_busy() for the parent >> driver (stm32-adc-core), synchronously with the child driver (stm32-adc), >> to avoid this. >> >> Fixes: 9bdbb1139ca1 ("iio: adc: stm32-adc: add power management support") >> >> Signed-off-by: Fabrice Gasnier > > Hi Fabrice, > > Whilst this will clearly work, it seems like a somewhat adhoc solution. > Power management specialists (cc'd): Is this what we should be doing, or > have Fabrice and I both missed something that we should be doing here? Hi all, PM specialists, As per my understanding, pm_runtime_mark_last_busy() doesn't cascade to the parent device: - in pm_runtime.h: static inline void pm_runtime_mark_last_busy(struct device *dev) { WRITE_ONCE(dev->power.last_busy, ktime_get_mono_fast_ns()); } STM32 ADC driver uses a model with an autosupsend delay for - a parent driver to handle common resources, registers etc. - child drivers for each ADC. So the question is on how to fix the behavior I described: 1: Child activity with "short" autosuspend_delay 2: Parent activity with "longer" autosuspend_delay _ _ _ _ _ _ _ _ 1: _| |___| |___| |___| |___| |_..._| |___| |___| |_... v v v v v v v v v v ... v v v v v v | | | | | +- pm_runtime_mark_last_busy() | | | +- pm_runtime_put_autosuspend() v | | | | +--- pm_runtime_get_sync() | v | | | +---> expires after autosuspend_delay | | | | | v v v _______________________________________ ___... 2: _| ... |___| Glitches on parent dev near autosuspend_delay ^ - does the child driver needs to "kick" parent driver with pm_runtime_mark_last_busy(), as proposed in current patch ? - or is it something that should be done by PM runtime core routines ? e.g. make pm_runtime_mark_last_busy() recursive or something else ? Please advise Best regards, Fabrice > > Thanks, > > Jonathan > >> --- >> drivers/iio/adc/stm32-adc.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c >> index 3b291d7..670157e 100644 >> --- a/drivers/iio/adc/stm32-adc.c >> +++ b/drivers/iio/adc/stm32-adc.c >> @@ -1157,6 +1157,7 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev, >> >> stm32_adc_conv_irq_disable(adc); >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1278,6 +1279,7 @@ static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev, >> adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength); >> >> ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask); >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1329,6 +1331,7 @@ static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev, >> else >> *readval = stm32_adc_readl(adc, reg); >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1451,6 +1454,7 @@ static int __stm32_adc_buffer_postenable(struct iio_dev *indio_dev) >> err_clr_trig: >> stm32_adc_set_trig(indio_dev, NULL); >> err_pm_put: >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1487,6 +1491,7 @@ static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev) >> if (stm32_adc_set_trig(indio_dev, NULL)) >> dev_err(&indio_dev->dev, "Can't clear trigger\n"); >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> } >> @@ -1874,6 +1879,7 @@ static int stm32_adc_probe(struct platform_device *pdev) >> goto err_hw_stop; >> } >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >