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,SPF_HELO_NONE,SPF_PASS,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 01C73C433FE for ; Mon, 6 Sep 2021 17:34:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D1B5761004 for ; Mon, 6 Sep 2021 17:34:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243942AbhIFRfX convert rfc822-to-8bit (ORCPT ); Mon, 6 Sep 2021 13:35:23 -0400 Received: from relay10.mail.gandi.net ([217.70.178.230]:51947 "EHLO relay10.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243799AbhIFRfV (ORCPT ); Mon, 6 Sep 2021 13:35:21 -0400 Received: (Authenticated sender: miquel.raynal@bootlin.com) by relay10.mail.gandi.net (Postfix) with ESMTPSA id CFCAA24000A; Mon, 6 Sep 2021 17:34:14 +0000 (UTC) Date: Mon, 6 Sep 2021 19:34:13 +0200 From: Miquel Raynal To: Jonathan Cameron Cc: "Sa, Nuno" , Lars-Peter Clausen , Thomas Petazzoni , "linux-iio@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 03/16] iio: adc: max1027: Push only the requested samples Message-ID: <20210906193413.1892f0c8@xps13> In-Reply-To: <20210906175657.62cb0bc6@jic23-huawei> References: <20210818111139.330636-1-miquel.raynal@bootlin.com> <20210818111139.330636-4-miquel.raynal@bootlin.com> <20210830110756.733d5201@jic23-huawei> <20210830152956.58331a8d@jic23-huawei> <20210901101209.31703187@xps13> <20210906175657.62cb0bc6@jic23-huawei> Organization: Bootlin X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jonathan, jic23@kernel.org wrote on Mon, 6 Sep 2021 17:56:57 +0100: > On Mon, 6 Sep 2021 08:59:55 +0000 > "Sa, Nuno" wrote: > > > > -----Original Message----- > > > From: Miquel Raynal > > > Sent: Wednesday, September 1, 2021 10:12 AM > > > To: Sa, Nuno > > > Cc: Jonathan Cameron ; Lars-Peter Clausen > > > ; Thomas Petazzoni > > > ; linux-iio@vger.kernel.org; linux- > > > kernel@vger.kernel.org > > > Subject: Re: [PATCH 03/16] iio: adc: max1027: Push only the requested > > > samples > > > > > > [External] > > > > > > Hello, > > > > > > "Sa, Nuno" wrote on Mon, 30 Aug 2021 > > > 15:02:26 > > > +0000: > > > > > > > > -----Original Message----- > > > > > From: Jonathan Cameron > > > > > Sent: Monday, August 30, 2021 4:30 PM > > > > > To: Sa, Nuno > > > > > Cc: Miquel Raynal ; Lars-Peter > > > Clausen > > > > > ; Thomas Petazzoni > > > > > ; linux-iio@vger.kernel.org; > > > linux- > > > > > kernel@vger.kernel.org > > > > > Subject: Re: [PATCH 03/16] iio: adc: max1027: Push only the > > > requested > > > > > samples > > > > > > > > > > [External] > > > > > > > > > > On Mon, 30 Aug 2021 10:49:50 +0000 > > > > > "Sa, Nuno" wrote: > > > > > > > > > > > > -----Original Message----- > > > > > > > From: Jonathan Cameron > > > > > > > Sent: Monday, August 30, 2021 12:08 PM > > > > > > > To: Sa, Nuno > > > > > > > Cc: Miquel Raynal ; Lars-Peter > > > > > Clausen > > > > > > > ; Thomas Petazzoni > > > > > > > ; linux-iio@vger.kernel.org; > > > > > linux- > > > > > > > kernel@vger.kernel.org > > > > > > > Subject: Re: [PATCH 03/16] iio: adc: max1027: Push only the > > > > > requested > > > > > > > samples > > > > > > > > > > > > > > [External] > > > > > > > > > > > > > > On Fri, 20 Aug 2021 07:10:48 +0000 > > > > > > > "Sa, Nuno" wrote: > > > > > > > > > > > > > > > > -----Original Message----- > > > > > > > > > From: Miquel Raynal > > > > > > > > > Sent: Wednesday, August 18, 2021 1:11 PM > > > > > > > > > To: Jonathan Cameron ; Lars-Peter > > > Clausen > > > > > > > > > > > > > > > > > > Cc: Thomas Petazzoni ; > > > linux- > > > > > > > > > iio@vger.kernel.org; linux-kernel@vger.kernel.org; Miquel > > > > > Raynal > > > > > > > > > > > > > > > > > > Subject: [PATCH 03/16] iio: adc: max1027: Push only the > > > > > requested > > > > > > > > > samples > > > > > > > > > > > > > > > > > > [External] > > > > > > > > > > > > > > > > > > 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 but only the desired channels will be > > > > > pushed > > > > > > > to > > > > > > > > > the IIO buffers. > > > > > > > > > > > > > > > > > > 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; > > > > > > > > > + > > > > > > > > > > > > > > > > I'm not sure this can actually happen. If you try to enable the > > > > > buffer > > > > > > > > with no scan element, it should give you an error before you > > > > > reach > > > > > > > > this point... > > > > > > > > > > > > > > > > > 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); > > > > > > > > > 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; > > > > > > > > > > > > > > > > I think sparse will complain here. buffer is a __be16 restricted > > > > > > > > type so you should not mix those... > > > > > > > > > + unsigned int bit; > > > > > > > > > > > > > > > > > > pr_debug("%s(irq=%d, private=0x%p)\n", __func__, > > > > > irq, > > > > > > > > > > > > > > > > > > > > > > > > private);in/20210818_miquel_raynal_bring_software_triggers_support > > > > > > > _to_max1027_like_adcs.mbx > > > > > > > > > > > > > > > > > > /* 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]; > > > > > > > > > > > > > > > > Since we are here, when looking into the driver, I realized > > > > > > > > that st->buffer is not DMA safe. In IIO, we kind of want to > > > > > enforce > > > > > > > > that all buffers that are passed to spi/i2c buses are safe... > > > Maybe > > > > > > > > this is something you can include in your series. > > > > > > > > > > > > > > Why is it not? st->buffer is result of a devm_kmalloc_array() > > > call > > > > > and > > > > > > > that should provide a DMA safe buffer as I understand it. > > > > > > > > > > > > > > > > > > > That's a good question. I'm not sure how I came to that > > > conclusion > > > > > which > > > > > > is clearly wrong. Though I think the buffer might share the line > > > with > > > > > the > > > > > > mutex... > > > > > Pointer shares a line. The buffer it points to doesn't as allocated > > > > > by separate heap allocation. > > > > > > > > > > > > > Ups, sure :facepalm: > > > > > > My understanding [1] was that devm_ allocations were generally not > > > suitable for DMA and should not be used for this particular purpose > > > because of the extra 16 bytes allocated for storing the devm magic > > > somewhere, which shifts the entire buffer and prevents it to always > > > be > > > aligned on a cache line. I will propose a patch to switch to > > > kmalloc_array() instead. > > > > I do not think this is a problem anymore [1]. Nowadays, 'devm_kmalloc' > > should give you the same alignment guarantees as 'kmalloc' > > > > [1]: https://elixir.bootlin.com/linux/latest/source/drivers/base/devres.c#L35 > Great info. I remembered a discussion about fixing that, but couldn't find > the patch. For some reason I didn't just check the code :) Nice! I didn't know about that, thanks a lot for sharing. So this patch can be safely discarded then. Thanks, Miquèl