From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) (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 667BE26D4F2 for ; Tue, 15 Jul 2025 07:52:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752565932; cv=none; b=FHtgtCGcs1AJewa5YpJHJMoSqIIbPgmb92eh1tKcLHSM6XzTH3gj42PBcYEQ8h/+jKA3yF4B+L+u7Eo3v5XYQvD35VtX/RG2vkgouGIdLih7K33966Vik/uK9smpKlgufnTkVD+HOuq6wQF3DsuXpj4mJwyYpll/vZEXAnHStWY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752565932; c=relaxed/simple; bh=9kafQ4EvbyNb+0AXntVH1c17Mp47HMZ46/b+y7UAQjc=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KDT6jIp6ajW+Sz0ushsH8QBAkaNYJHM6IcQUmRbD4JdDjVlPTf4Vo56jV7rsthWizz0egRcp/egNOiHdPaNqb+D13UMpEuArfbm7vpMj/J3uOdTP0aGiO9S71kWRXNr8Z1FZma7z9EYnXkJaixu6WyU1qQH3w+NfkwWTQZtDA+4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=K2ZBOvpC; arc=none smtp.client-ip=217.70.183.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="K2ZBOvpC" Received: by mail.gandi.net (Postfix) with ESMTPSA id 15E884430B; Tue, 15 Jul 2025 07:52:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1752565927; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M1C4N9WQ5rgNkJxYdso36BOZpEKSkeehMURg6RF2AZs=; b=K2ZBOvpCK+DfbORKkUB96qZGojQMOpxKddXHomukQBEYBIN0+lWkj1YulbBi+zfeCRljce ttBunNrQzmnhlqdvoJbaUegatps4qvodXqUHBZkfHJL+5voqtr1E8uuAGwzADYFEH7FiUv pWMHI2VPjx0aq+v9NotfmbpIiBWLLYL7iCLnS9n3yx6Mv/TuPYng8bkmj4mw489w22m1Jh jMqSVGWUuQLOuwffNXsCwGnXjUHX1LAbH3NLppNQIhnxhMVvm0DC1sKPw4Lw5QG7yER/0y iG/DOx+uuN7YWl+GRAg7T3C+vCELR/4CaTsXl+WJvZzjKfmB+yM0p0i0Ygz9tg== Date: Tue, 15 Jul 2025 09:52:01 +0200 From: Herve Codina To: Rob Herring Cc: Andrew Lunn , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Michael Turquette , Stephen Boyd , Andi Shyti , Wolfram Sang , Peter Rosin , Derek Kiernan , Dragan Cvetic , Arnd Bergmann , Saravana Kannan , Bjorn Helgaas , Mark Brown , Len Brown , Andy Shevchenko , Daniel Scally , Heikki Krogerus , Sakari Ailus , Wolfram Sang , Geert Uytterhoeven , Davidlohr Bueso , Dave Jiang , Alison Schofield , Vishal Verma , Ira Weiny , Dan Williams , linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, linux-i2c@vger.kernel.org, devicetree@vger.kernel.org, linux-pci@vger.kernel.org, linux-spi@vger.kernel.org, linux-acpi@vger.kernel.org, linux-cxl@vger.kernel.org, Allan Nielsen , Horatiu Vultur , Steen Hegelund , Luca Ceresoli , Thomas Petazzoni Subject: Re: [PATCH v3 05/28] bus: simple-pm-bus: Populate child nodes at probe Message-ID: <20250715095201.1bcb4ab7@bootlin.com> In-Reply-To: References: <20250613134817.681832-1-herve.codina@bootlin.com> <20250613134817.681832-6-herve.codina@bootlin.com> <20250627155200.GB3234475-robh@kernel.org> <20250703093302.4f7743ea@bootlin.com> <20250704105725.50cb72b9@bootlin.com> Organization: Bootlin X-Mailer: Claws Mail 4.3.1 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtdefgdehgedvjecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfitefpfffkpdcuggftfghnshhusghstghrihgsvgenuceurghilhhouhhtmecufedtudenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepfffhvfevuffkjghfohfogggtgfesthekredtredtjeenucfhrhhomhepjfgvrhhvvgcuvehoughinhgruceohhgvrhhvvgdrtghoughinhgrsegsohhothhlihhnrdgtohhmqeenucggtffrrghtthgvrhhnpeeviefffeegiedtleelieeghfejleeuueevkeevteegffehledtkeegudeigffgvdenucfkphepvdgrtddumegvtdgrmedvkeehmegsleektdemvgegtdgtmeeitgegfeemsgehsggsmegrgedvkeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpedvrgdtudemvgdtrgemvdekheemsgelkedtmegvgedttgemiegtgeefmegshegssgemrgegvdekpdhhvghloheplhhotggrlhhhohhsthdpmhgrihhlfhhrohhmpehhvghrvhgvrdgtohguihhnrgessghoohhtlhhinhdrtghomhdpnhgspghrtghpthhtohepgeekpdhrtghpthhtoheprhhosghhsehkvghrnhgvlhdrohhrghdprhgtphhtthhopegrnhgurhgvfieslhhunhhnrdgthhdprhgtphhtthhopehgrhgvghhkhheslhhinhhugihfohhunhgurghtihhonhdrohhrghdprhgtphhtthhopehrrghfrggvlheskhgvrhhnvghlrdhorhhgp dhrtghpthhtohepuggrkhhrsehkvghrnhgvlhdrohhrghdprhgtphhtthhopehshhgrfihnghhuoheskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepshdrhhgruhgvrhesphgvnhhguhhtrhhonhhigidruggvpdhrtghpthhtohepkhgvrhhnvghlsehpvghnghhuthhrohhnihigrdguvg X-GND-Sasl: herve.codina@bootlin.com Hi Rob, On Mon, 14 Jul 2025 12:44:22 -0500 Rob Herring wrote: > On Fri, Jul 4, 2025 at 3:57 AM Herve Codina wrote: > > > > Hi Rob, > > > > On Thu, 3 Jul 2025 09:33:02 +0200 > > Herve Codina wrote: > > > > > Hi Rob, > > > > > > On Fri, 27 Jun 2025 10:52:00 -0500 > > > Rob Herring wrote: > > > > > > > On Fri, Jun 13, 2025 at 03:47:45PM +0200, Herve Codina wrote: > > > > > The simple-pm-bus driver handles several simple busses. When it is used > > > > > with busses other than a compatible "simple-pm-bus", it doesn't populate > > > > > its child devices during its probe. > > > > > > > > > > This confuses fw_devlink and results in wrong or missing devlinks. > > > > > > > > > > Once a driver is bound to a device and the probe() has been called, > > > > > device_links_driver_bound() is called. > > > > > > > > > > This function performs operation based on the following assumption: > > > > > If a child firmware node of the bound device is not added as a > > > > > device, it will never be added. > > > > > > > > > > Among operations done on fw_devlinks of those "never be added" devices, > > > > > device_links_driver_bound() changes their supplier. > > > > > > > > > > With devices attached to a simple-bus compatible device, this change > > > > > leads to wrong devlinks where supplier of devices points to the device > > > > > parent (i.e. simple-bus compatible device) instead of the device itself > > > > > (i.e. simple-bus child). > > > > > > > > > > When the device attached to the simple-bus is removed, because devlinks > > > > > are not correct, its consumers are not removed first. > > > > > > > > > > In order to have correct devlinks created, make the simple-pm-bus driver > > > > > compliant with the devlink assumption and create its child devices > > > > > during its probe. > > > > > > > > IIRC, skipping child nodes was because there were problems with > > > > letting the driver handle 'simple-bus'. How does this avoid that now? > > > > > > I don't know about the specific issues related to those problems. Do you > > > have some pointers about them? > > > > > > > > > > > The root of_platform_populate() that created the simple-bus device that > > > > gets us to the probe here will continue descending into child nodes. > > > > Meanwhile, the probe here is also descending into those same child > > > > nodes. Best case, that's just redundant. Worst case, won't you still > > > > have the same problem if the first of_platform_populate() creates the > > > > devices first? > > > > > > > > > > Maybe we could simply avoid of_platform_populate() to be recursive when a > > > device populate by of_platform_populate() is one of devices handled by > > > the simple-bus driver and let the simple-bus driver do the job. > > > > > > of_platform_populate will handle the first level. It will populate children > > > of the node given to of_platform_populate() and the children of those > > > children will be populate by the simple-bus driver. > > > > > > I could try a modification in that way. Do you think it could be a correct > > > solution? > > > > > > > I have started to look at this solution and it's going to be more complex > > than than I thought. > > > > Many MFD drivers uses a compatible of this kind (the same exist for bus > > driver with "simple-bus"): > > compatible = "foo,bar", "simple-mfd"; > > > > Usually the last compatible string ("simple-mfd" here) is a last fallback > > and the first string is the more specific one. > > > > In the problematic case, "foo,bar" has a specific driver and the driver > > performs some operations at probe() but doesn't call of_platform_populate() > > and relies on the core to do the device creations (recursively) based on > > the "simple,mfd" string present in the compatible property. > > > > Some other calls of_platform_populate() in they probe (which I think is > > correct) and in that case, the child device creation can be done at two > > location: specific driver probe() and core. > > > > You pointed out that the core could create devices before the specific > > driver is probed. In that case, some of existing drivers calling > > of_platform_populate() are going to have issues. > > > > I can try to modify existing MFD and bus drivers (compatible fallback to > > simple-mfd, simple-bus, ...) in order to have them call of_platform_populate() > > in they probe() and after all problematic drivers are converted, the > > recursive creation of devices done in the core could be removed. > > The problem is how does a bus driver know if there is a specific MFD > driver or not? It doesn't. The MFD driver could be a module and loaded > any time later. We'd really need some sort of unbind the generic > driver and re-bind to a more specific driver when and if that driver > appears. We could perhaps have a list of devices with a driver because > in theory that should be a short list as the (broken) promise of > simple-mfd is the child nodes have no dependency on the parent node > which implies the parent doesn't have a driver. The specific > compatible is there in case that assumption turns out wrong. > Hum, I see. In my use case, I don't use MFD drivers but only simple-bus compatible. I think your point is also relevant with simple-bus. Indeed how does a parent bus driver know if there is a specific bus driver that handles the child simple-bus compatible one in case of 'simple-bus' used as fallback. Related to your proposal related to the "list of devices with a driver", what do you mean? I don't see how to set this kind of list. Can you give me some pointers? If I understood the discussion, the issue seems that 'simple-bus' can't populate unconditionally children at his probe. The possible recursion in creating devices done by of_platform_populate() should be kept and 'simple-bus' should rely on that. The other solution that fixes my use case is to use an other compatible string. Would you accept a new compatible string: "simple-platform-bus"? In simple-pm-bus.c, this compatible would populate children at probe. In fact, it will act the same way as 'simple-pm-bus' without looking at clocks nor handling pm_runtime. Best regards, Hervé