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=-15.5 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 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 9EFBBC4320A for ; Mon, 30 Aug 2021 10:03:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84464610A2 for ; Mon, 30 Aug 2021 10:03:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236290AbhH3KED (ORCPT ); Mon, 30 Aug 2021 06:04:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:51714 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231708AbhH3KEA (ORCPT ); Mon, 30 Aug 2021 06:04:00 -0400 Received: from jic23-huawei (cpc108967-cmbg20-2-0-cust86.5-4.cable.virginm.net [81.101.6.87]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D77F461090; Mon, 30 Aug 2021 10:03:04 +0000 (UTC) Date: Mon, 30 Aug 2021 11:06:16 +0100 From: Jonathan Cameron To: Miquel Raynal Cc: Lars-Peter Clausen , Thomas Petazzoni , linux-iio@vger.kernel.org, Subject: Re: [PATCH 03/16] iio: adc: max1027: Push only the requested samples Message-ID: <20210830110616.70672ef3@jic23-huawei> In-Reply-To: <20210818111139.330636-4-miquel.raynal@bootlin.com> References: <20210818111139.330636-1-miquel.raynal@bootlin.com> <20210818111139.330636-4-miquel.raynal@bootlin.com> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.30; 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-kernel@vger.kernel.org On Wed, 18 Aug 2021 13:11:26 +0200 Miquel Raynal wrote: > When a triggered scan occurs, the identity of the desired channels is > known in indio_dev->active_scan_mask. Instead of reading and pushing to > the IIO buffers all channels each time, scan the minimum amount of > channels (0 to maximum requested chan, to be exact) and only provide the > samples requested by the user. > > For example, if the user wants channels 1, 4 and 5, all channels from > 0 to 5 will be scanned That's a reasonably optimisation > but only the desired channels will be pushed to > the IIO buffers. Don't do this last bit. The core handles demuxing the channels via active_scan_masks. As a general rule it does a more efficient job of this than a hand coded version in a driver (precached copy rules etc). The core has to have the logic anyway to support multiple consumers (e.g. in kernel consumer and userspace) so we reuse it for these cases. > > Signed-off-by: Miquel Raynal > --- > drivers/iio/adc/max1027.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c > index b753658bb41e..8ab660f596b5 100644 > --- a/drivers/iio/adc/max1027.c > +++ b/drivers/iio/adc/max1027.c > @@ -360,6 +360,9 @@ static int max1027_set_trigger_state(struct iio_trigger *trig, bool state) > struct max1027_state *st = iio_priv(indio_dev); > int ret; > > + if (bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength)) > + return -EINVAL; > + > if (state) { > /* Start acquisition on cnvst */ > st->reg = MAX1027_SETUP_REG | MAX1027_CKS_MODE0 | > @@ -368,9 +371,12 @@ static int max1027_set_trigger_state(struct iio_trigger *trig, bool state) > if (ret < 0) > return ret; > > - /* Scan from 0 to max */ > - st->reg = MAX1027_CONV_REG | MAX1027_CHAN(0) | > - MAX1027_SCAN_N_M | MAX1027_TEMP; > + /* > + * Scan from 0 to the highest requested channel. The temperature > + * could be avoided but it simplifies a bit the logic. > + */ > + st->reg = MAX1027_CONV_REG | MAX1027_SCAN_0_N | MAX1027_TEMP; > + st->reg |= MAX1027_CHAN(fls(*indio_dev->active_scan_mask) - 2); This should be combined with appropriate additions to available_scan_masks arrays so the IIO core can handle choosing the right one to match enabled channels. > ret = spi_write(st->spi, &st->reg, 1); > if (ret < 0) > return ret; > @@ -391,11 +397,22 @@ static irqreturn_t max1027_trigger_handler(int irq, void *private) > struct iio_poll_func *pf = private; > struct iio_dev *indio_dev = pf->indio_dev; > struct max1027_state *st = iio_priv(indio_dev); > + unsigned int scanned_chans = fls(*indio_dev->active_scan_mask); > + u16 *buf = st->buffer; > + unsigned int bit; > > pr_debug("%s(irq=%d, private=0x%p)\n", __func__, irq, private); > > /* fill buffer with all channel */ > - spi_read(st->spi, st->buffer, indio_dev->masklength * 2); > + spi_read(st->spi, st->buffer, scanned_chans * 2); > + > + /* Only keep the channels selected by the user */ > + for_each_set_bit(bit, indio_dev->active_scan_mask, > + indio_dev->masklength) { > + if (buf[0] != st->buffer[bit]) > + buf[0] = st->buffer[bit]; > + buf++; > + } > > iio_push_to_buffers(indio_dev, st->buffer); >