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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 1567FC43331 for ; Tue, 26 Jan 2021 19:22:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA3C722B2C for ; Tue, 26 Jan 2021 19:22:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388663AbhAZFpX (ORCPT ); Tue, 26 Jan 2021 00:45:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43964 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727892AbhAYMP2 (ORCPT ); Mon, 25 Jan 2021 07:15:28 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDE22C061788 for ; Mon, 25 Jan 2021 03:21:37 -0800 (PST) Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=[IPv6:::1]) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1l3zw8-0002Wp-6x; Mon, 25 Jan 2021 12:21:36 +0100 Subject: Re: [PATCH v2] iio: adc: stm32-adc: enable timestamping for non-DMA usage To: Jonathan Cameron Cc: Lars-Peter Clausen , Peter Meerwald-Stadler , Maxime Coquelin , Alexandre Torgue , kernel@pengutronix.de, Holger Assmann , Fabrice Gasnier , linux-iio@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20210122113355.32384-1-a.fatoum@pengutronix.de> <20210124152212.5bc39e57@archlinux> From: Ahmad Fatoum Message-ID: <04385c49-8f27-a159-b033-a62cdfbda824@pengutronix.de> Date: Mon, 25 Jan 2021 12:21:35 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210124152212.5bc39e57@archlinux> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: a.fatoum@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Jonathan, On 24.01.21 16:22, Jonathan Cameron wrote: > On Fri, 22 Jan 2021 12:33:55 +0100 > Ahmad Fatoum wrote: > >> For non-DMA usage, we have an easy way to associate a timestamp with a >> sample: iio_pollfunc_store_time stores a timestamp in the primary >> trigger IRQ handler and stm32_adc_trigger_handler runs in the IRQ thread >> to push out the buffer along with the timestamp. >> >> For this to work, the driver needs to register an IIO_TIMESTAMP channel. >> Do this. >> >> For DMA, it's not as easy, because we don't push the buffers out of >> stm32_adc_trigger, but out of stm32_adc_dma_buffer_done, which runs in >> a tasklet scheduled after a DMA completion. >> >> Preferably, the DMA controller would copy us the timestamp into that buffer >> as well. Until this is implemented, restrict timestamping support to >> only PIO. For low-frequency sampling, PIO is probably good enough. >> >> Cc: Holger Assmann >> Acked-by: Fabrice Gasnier >> Signed-off-by: Ahmad Fatoum > > This patch itself is fine, but it will expose a potential bug. > > The buffer passed to iio_push_to_buffers_with_timestamp needs to be suitably > aligned to take an 8 byte timestamp and large enough to do so. > Currently, in this driver it isn't. > u16 buffer[STM32_ADC_MAX_SQ]; > Appears to be the same length as the channel count, and isn't 8 byte > aligned. (add __aligned(8) to fix that) > > Could you add that fix to this patch as well? Just done so, thanks. But I think it's very surprising API to expect a void * to have a specific alignment. Should this perhaps be encoded into the function signature? e.g. typedef void __aligned_u64_void __aligned(8); static inline int iio_push_to_buffers_with_timestamp(struct iio_dev *indio_dev, __aligned_u64_void *data, int64_t timestamp); [I assume put_unaligned_* isn't used for performance reasons?) Cheers, Ahmad > > Thanks, > > Jonathan > > >> --- >> v1 -> v2: >> - Added comment about timestamping being PIO only (Fabrice) >> - Added missing DMA resource clean up in error path (Fabrice) >> - Added Fabrice's Acked-by >> --- >> drivers/iio/adc/stm32-adc.c | 35 +++++++++++++++++++++++++++++------ >> 1 file changed, 29 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c >> index c067c994dae2..885bb514503c 100644 >> --- a/drivers/iio/adc/stm32-adc.c >> +++ b/drivers/iio/adc/stm32-adc.c >> @@ -1718,7 +1718,7 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev, >> } >> } >> >> -static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) >> +static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping) >> { >> struct device_node *node = indio_dev->dev.of_node; >> struct stm32_adc *adc = iio_priv(indio_dev); >> @@ -1766,6 +1766,9 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) >> return -EINVAL; >> } >> >> + if (timestamping) >> + num_channels++; >> + >> channels = devm_kcalloc(&indio_dev->dev, num_channels, >> sizeof(struct iio_chan_spec), GFP_KERNEL); >> if (!channels) >> @@ -1816,6 +1819,19 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) >> stm32_adc_smpr_init(adc, channels[i].channel, smp); >> } >> >> + if (timestamping) { >> + struct iio_chan_spec *timestamp = &channels[scan_index]; >> + >> + timestamp->type = IIO_TIMESTAMP; >> + timestamp->channel = -1; >> + timestamp->scan_index = scan_index; >> + timestamp->scan_type.sign = 's'; >> + timestamp->scan_type.realbits = 64; >> + timestamp->scan_type.storagebits = 64; >> + >> + scan_index++; >> + } >> + >> indio_dev->num_channels = scan_index; >> indio_dev->channels = channels; >> >> @@ -1875,6 +1891,7 @@ static int stm32_adc_probe(struct platform_device *pdev) >> struct device *dev = &pdev->dev; >> irqreturn_t (*handler)(int irq, void *p) = NULL; >> struct stm32_adc *adc; >> + bool timestamping = false; >> int ret; >> >> if (!pdev->dev.of_node) >> @@ -1931,16 +1948,22 @@ static int stm32_adc_probe(struct platform_device *pdev) >> if (ret < 0) >> return ret; >> >> - ret = stm32_adc_chan_of_init(indio_dev); >> - if (ret < 0) >> - return ret; >> - >> ret = stm32_adc_dma_request(dev, indio_dev); >> if (ret < 0) >> return ret; >> >> - if (!adc->dma_chan) >> + if (!adc->dma_chan) { >> + /* For PIO mode only, iio_pollfunc_store_time stores a timestamp >> + * in the primary trigger IRQ handler and stm32_adc_trigger_handler >> + * runs in the IRQ thread to push out buffer along with timestamp. >> + */ >> handler = &stm32_adc_trigger_handler; >> + timestamping = true; >> + } >> + >> + ret = stm32_adc_chan_of_init(indio_dev, timestamping); >> + if (ret < 0) >> + goto err_dma_disable; >> >> ret = iio_triggered_buffer_setup(indio_dev, >> &iio_pollfunc_store_time, handler, > > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |