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Message-ID: <YhZI1XImMNJgzORb@smile.fi.intel.com> Date: Wed, 23 Feb 2022 16:46:45 +0200 From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com> To: Clément Léger <clement.leger@...tlin.com>, Hans de Goede <hdegoede@...hat.com>, Enrico Weigelt <info@...ux.net> Cc: Daniel Scally <djrscally@...il.com>, Heikki Krogerus <heikki.krogerus@...ux.intel.com>, Sakari Ailus <sakari.ailus@...ux.intel.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J . Wysocki" <rafael@...nel.org>, Wolfram Sang <wsa@...nel.org>, Peter Rosin <peda@...ntia.se>, Russell King <linux@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org, linux-i2c@...r.kernel.org, netdev@...r.kernel.org, Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Alexandre Belloni <alexandre.belloni@...tlin.com> Subject: Re: [RFC 00/10] add support for fwnode in i2c mux system and sfp On Tue, Feb 22, 2022 at 05:30:19PM +0100, Clément Léger wrote: > Le Mon, 21 Feb 2022 19:41:24 +0200, > Andy Shevchenko <andriy.shevchenko@...ux.intel.com> a écrit : > > > We thought about adding CONFIG_OF to x86 and potentially describe this > > > card using device-tree overlays but it introduce other problems that > > > also seems difficult to solve (overlay loading without base > > > device-tree, fixup of IRQs, adresses, and so on) and CONFIG_OF is not > > > often enabled on x86 to say the least. > > > > Why it can't be described by SSDT overlay (if the x86 platform in question is > > ACPI based)? > > This devices uses a SoC for which drivers are already available but are > meant to be used by a device-tree description. These drivers uses the > following subsystems: > - reset (no ACPI support ?) > - clk (no ACPI support ?) > - pinctrl (no ACPI support ?) > - syscon (no ACPI support ?) > - gpio > - phy > - mdio > > Converting existing OF support to fwnode support and thus allowing > drivers and subsystems to be compatible with software nodes seemed like > the easiest way to do what I needed by keeping all existing drivers. > With this support, the driver is completely self-contained and does > allow the card to be plugged on whatever platform the user may have. I agree with Hans on the point that converting to / supporting fwnode is a good thing by its own. > Again, the PCI card is independent of the platform, I do not really see > why it should be described using platform description language. Yep, and that why it should cope with the platforms it's designed to be used with. > > > This series introduce a number of changes in multiple subsystems to > > > allow registering and using devices that are described with a > > > software_node description attached to a mfd_cell, making them usable > > > with the fwnode API. It was needed to modify many subsystem where > > > CONFIG_OF was tightly integrated through the use of of_xlate() > > > functions and other of_* calls. New calls have been added to use fwnode > > > API and thus be usable with a wider range of nodes. Functions that are > > > used to get the devices (pinctrl_get, clk_get and so on) also needed > > > to be changed to use the fwnode API internally. > > > > > > For instance, the clk framework has been modified to add a > > > fwnode_xlate() callback and a new named fwnode_clk_add_hw_provider() > > > has been added. This function will register a clock using > > > fwnode_xlate() callback. Note that since the fwnode API is compatible > > > with devices that have a of_node member set, it will still be possible > > > to use the driver and get the clocks with CONFIG_OF enabled > > > configurations. > > > > How does this all is compatible with ACPI approaches? > > I mean we usually do not reintroduce 1:1 DT schemas in ACPI. > > For the moment, I only added fwnode API support as an alternative to > support both OF and software nodes. ACPI is not meant to be handled by > this code "as-is". There is for sure some modifications to be made and > I do not know how clocks are handled when using ACPI. Based on some > thread dating back to 2018 [1], it seem it was even not supported at > all. > > To be clear, I added the equivalent of the OF support but using > fwnode API because I was interested primarly in using it with software > nodes and still wanted OF support to work. I did not planned it to be > "ACPI compliant" right now since I do not have any knowledge in that > field. And here is the problem. We have a few different resource providers (a.k.a. firmware interfaces) which we need to cope with. What is going on in this series seems to me quite a violation of the layers and technologies. But I guess you may find a supporter of your ideas (I mean Enrico). However, I'm on the other side and do not like this approach. > > I think the CCF should be converted to use fwnode APIs and meanwhile > > we may discuss how to deal with clocks on ACPI platforms, because > > it may be a part of the power management methods. > > Ok, before going down that way, should the fwnode support be the "only" > one, ie remove of_clk_register and others and convert them to > fwnode_clk_register for instance or should it be left to avoid > modifying all clock drivers ? IRQ domain framework decided to cohabit both, while deprecating the OF one. (see "add" vs. "create" APIs there). I think it's a sane choice. > > > In some subsystems, it was possible to keep OF related function by > > > wrapping the fwnode ones. It is not yet sure if both support > > > (device-tree and fwnode) should still continue to coexists. For instance > > > if fwnode_xlate() and of_xlate() should remain since the fwnode version > > > also supports device-tree. Removing of_xlate() would of course require > > > to modify all drivers that uses it. > > > > > > Here is an excerpt of the lan966x description when used as a PCIe card. > > > The complete description is visible at [2]. This part only describe the > > > flexcom controller and the fixed-clock that is used as an input clock. > > > > > > static const struct property_entry ddr_clk_props[] = { > > > PROPERTY_ENTRY_U32("clock-frequency", 30000000), > > > > > PROPERTY_ENTRY_U32("#clock-cells", 0), > > > > Why this is used? > > These props actually describes a fixed-clock properties. When adding > fwnode support to clk framework, it was needed to add the > equivalent of of_xlate() for fwnode (fwnode_xlate()). The number of > cells used to describe a reference is still needed to do the > translation using fwnode_property_get_reference_args() and give the > correct arguments to fwnode_xlate(). What you described is the programming (overkilled) point. But does hardware needs this? I.o.w. does it make sense in the _hardware_ description? > [1] > https://lore.kernel.org/lkml/914341e7-ca94-054d-6127-522b745006b4@arm.com/T/ -- With Best Regards, Andy Shevchenko
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