From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2353D38F65C; Thu, 17 Sep 2026 02:46:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789613185; cv=none; b=Uq/B7bRF2iRyUp6JGyCplIeCSr3GgeBo1RiWcCHzmBK6ef54jEKMUhWHXE6oQBfrtSMHl1Y1SdMeSJIHRu9Q0wSLiZRrjnkpbUQF5nk7mUKHbytB3EGidnKT/TH/q85Z5FwpcUJg8mn1N/qRo/OXTChKymtL2eCB3YDEdUfAsOE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789613185; c=relaxed/simple; bh=Z4F4UlJd7/nPmUh0RCHmV43t2CGkZbgLC7yVMcbuN70=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Hq/0wzoGwAr9PD9GXUv5tbw8HDOtkKfPUEO9e8wHL4B5zFH2bWR4Wghy+gBNC+gR0w6ZaEZ8Qjz6IeA2TgOfjjUyxjqoaBduyvsWTYSHBgxgbKpPdfVFYjomP014ZSZDkj/pNpIwuzSgioP/GwD+Rdu8LXdVzvw+ubbWhc1wD1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P5dPvW7Q; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="P5dPvW7Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8C8F1F000FF; Thu, 17 Sep 2026 02:46:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789613174; bh=UN5Huh0snw2hAqQl+cycuS2Mfq3pAGMsrgQd6J2731E=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=P5dPvW7QRJIKLFjc1ZdtupFsBUxzp6xNVgq0O7qemg2PR9SXo3gemALz2h42fx+x4 BOF9rA+fq64kt1ZRIvqnwkfotGFdNtdU9qScNOBWf51Ulbbba9T12tpAJIVIuEXYMe g0DKzk0dmY4YDwCH8vmGyly4eTHmPWvXnhZSgaDIt5OvV1puEJYkAkxoZZOl2WPo5P 0cDfchwsLqyNlX5cEcZ6EQj8uVkrbqIYXWbaD6Yh2qxiHuW3NZC/QtDPL5Vp2uG7Rf Ob3riojHf1LNr/0o5Ctgx39WkZXbpba5OnLYxDBi4shoBPTzQJGEbYJ5lthzY4nnHf deby/u8cWbZfw== Date: Thu, 17 Sep 2026 03:46:07 +0100 From: Jonathan Cameron To: Esben Haabendal , "Martin Kepplinger" Cc: "Lars-Peter Clausen" , "Rob Herring" , "Krzysztof Kozlowski" , "Conor Dooley" , "Sean Nyekjaer" , "David Lechner" , Nuno =?UTF-8?B?U8Oh?= , "Andy Shevchenko" , "Martin Kepplinger" , "Christoph Muellner" , , , Subject: Re: [PATCH v8 9/9] iio: accel: mma8452: Support interrupt sharing Message-ID: <20260917034607.2674781e@jic23-hlaptop> In-Reply-To: <87y0d4pal0.fsf@geanix.com> References: <20260907-mma8452-open-drain-v8-0-c17407e22118@geanix.com> <20260907-mma8452-open-drain-v8-9-c17407e22118@geanix.com> <_9NG2PCqwv-AxkrhQVOkPVIgvYD4-t2CFH5W5HVBmr35w9xmX9v9FIraB1OPE8Ssbd_pjQqM-bq3DEAtRl78Sg==@protonmail.internalid> <20260914002203.5ca07dd0@jic23-hlaptop> <87y0d4pal0.fsf@geanix.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 14 Sep 2026 09:15:55 +0200 Esben Haabendal wrote: > "Jonathan Cameron" writes: > > > On Mon, 07 Sep 2026 16:51:04 +0200 > > Esben Haabendal wrote: > > > >> Adding support for sharing interrupt line with other device requires the > >> interrupt handler to handle runtime PM suspension properly, ignoring the > >> irq if the device is suspended (maybe even off). And while at it, we use > >> the PM reference to ensure we do not get suspended while processing an irq. > >> > >> In order to prevent the chip from raising irq while suspended (that is when > >> using fixed regulator, where suspend just means setting the device in > >> STANDBY mode), we disable all interrupt sources by clearing CTRL_REG4, and > >> then restores the value again when resuming. > >> > >> With that in place, it is safe to add the IRQF_SHARED flag. > >> > >> Keep in mind that the device by default is using push-pull for the irq pin, > >> which might require additional hardware design to allow interrupt sharing. > >> > >> Signed-off-by: Esben Haabendal > >> --- > >> drivers/iio/accel/mma8452.c | 67 +++++++++++++++++++++++++++++++++++++++------ > >> 1 file changed, 58 insertions(+), 9 deletions(-) > >> > >> diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c > >> index fda29df5d109..e521dca37f76 100644 > >> --- a/drivers/iio/accel/mma8452.c > >> +++ b/drivers/iio/accel/mma8452.c > >> @@ -120,6 +120,7 @@ > >> * @sleep_val: time in ms to sleep while waiting for drdy > >> * @ctrl_reg1: CTRL_REG1 register shadow value > >> * @data_cfg: DATA_CFG register shadow value > >> + * @ctrl_reg4: CTRL_REG4 register value to restore on resume > >> * @open_drain: true for irq pin in open-drain mode > >> */ > >> struct mma8452_data { > >> @@ -138,6 +139,7 @@ struct mma8452_data { > >> int sleep_val; > >> u8 ctrl_reg1; > >> u8 data_cfg; > >> + u8 ctrl_reg4; > >> bool open_drain; > >> }; > >> > >> @@ -1083,15 +1085,21 @@ static irqreturn_t mma8452_interrupt(int irq, void *p) > >> { > >> struct iio_dev *indio_dev = p; > >> struct mma8452_data *data = iio_priv(indio_dev); > >> + struct device *dev = &data->client->dev; > >> irqreturn_t ret = IRQ_NONE; > >> + int pm_status; > >> int src; > >> > >> + pm_status = pm_runtime_get_if_active(dev); > > > > Sashiko raises the question of what happens if you actually get an error > > return from this. You may be deliberately ignoring those, but if > > so add a comment. > > Yes, sounds like a good idea. > > > The fun race around tear down is worth considering in particular (see > > sashiko comment). > > I will look into that. Although very unlikely, it does sound like a real > issue that *could* occur. > > Adding a boolean flag (remove_in_progress = true) to the mma8452_data > struct, and set that in mma8452_remove() before disabling runtime pm > seems like a KISS solution. Should we be returning IRQ_HANDLED or > IRQ_NONE in that case? There is no IRQ_MAYBE return value :D This has been much debated. Personally I think IRQ_HANDLED because we don't know it is a spurious interrupt which is more or less all IRQ_NONE is useful for. Arguably doesn't matter as we don't expect many hits on this path and the spurious handling needs a lot before it does anything! > > >> + if (pm_status == 0) > >> + return IRQ_NONE; /* device is powered down */ > > > >> @@ -1784,29 +1796,62 @@ static void mma8452_remove(struct i2c_client *client) > >> #ifdef CONFIG_PM > >> static int mma8452_runtime_suspend(struct device *dev) > >> { > >> - struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev)); > >> + struct i2c_client *client = to_i2c_client(dev); > >> + struct iio_dev *indio_dev = i2c_get_clientdata(client); > >> struct mma8452_data *data = iio_priv(indio_dev); > >> int ret; > >> > >> - scoped_guard(mutex, &data->lock) > >> - ret = mma8452_standby(data); > >> + guard(mutex)(&data->lock); > > Mixing guards... > > Yes, I know. Resolving that turned out to be a bit more painful than I > thought. I do have that resolved in the next series I keep on talking > about. But distilling that as a separate patch for adding to this series > turned out to be impossible, as it relies on some of the other work, > like refactoring of the ACTIVE/STANDBY state handling (synchronization), > and most importantly, the switch to using regmap caching to properly > handle restoring of register values on resume. > > I am therefore hoping that we can find some way to agree on things here, > and then properly resolve it in the next series... Ok. It is fine for now. Perhaps add a comment along the lines of /* Must be first action in scope that needs to be undone on error */ And hopefully it won't be around long enough for anyone to copy it into more code! > > For what it is worth, in this very specific case, the only guard used is > first in the LIFO order, and will therefore be executed in exactly the > right order on exit, as it will run after all the goto cleanup, just as > the LIFO cleanup order requires. > > Obviously a fragile and undesirable way of doing error handling, but it > will go away again in the next series where I will eliminate the goto > error handling in mma8452_runtime_suspend(). >