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From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Rich Felker <dalias@libc.org>
Cc: Sekhar Nori <nsekhar@ti.com>, Kevin Hilman <khilman@kernel.org>,
	David Lechner <david@lechnology.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Frank Rowand <frowand.list@gmail.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Arend van Spriel <aspriel@gmail.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Michal Suchanek <msuchanek@suse.de>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	devicetree <devicetree@vger.kernel.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>
Subject: Re: [PATCH 00/11] platform: device tree support for early platform drivers
Date: Wed, 25 Apr 2018 11:33:42 +0200	[thread overview]
Message-ID: <CAMRc=Mcs4zR4oA3duX7z05x-5ZFfFteFx93Fm-s9gX+tU5vpsg@mail.gmail.com> (raw)
In-Reply-To: <20180424175752.GC3094@brightrain.aerifal.cx>

2018-04-24 19:57 GMT+02:00 Rich Felker <dalias@libc.org>:
> On Tue, Apr 24, 2018 at 07:30:40PM +0200, Bartosz Golaszewski wrote:
>> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>>
>> Device tree based systems often use OF_DECLARE() macros for devices
>> that need to be initialized early in the boot process such as clocks,
>> timers etc. However platform devices are more desirable.
>>
>> This series aims at introducing support for early platform drivers for
>> OF-based systems.
>>
>> The idea is to have a special compatible fallback string: "earlydev"
>> that similarily to "syscon" would be added to device nodes that need
>> early probing. We then need to call of_early_platform_populate() early
>> in the boot process to actually probe the registered devices.
>
> This makes no sense to me. It's not the device tree that should
> contain the knowledge that these need to be registered/probed early in
> the boot. That need is a property of the operating system/device
> drivers, and so the *drivers* should be the ones that contain the
> knowledge.
>
>> I am aware that this new compatible does not strictly correspond with
>> the "hardware description only" rule of DT, but we already have many
>> functionalities that break this rule: syscon, gpio hogs etc.
>>
>> The first user of this new functionality will be the DaVinci platform
>> for which we want to probe the pll, psc and timer drivers early in the
>> boot sequence but keep them implemented as platform drivers.
>>
>> In the future, if this series gets accepted, this could become and
>> alternative to TIMER_OF_DECLARE, CLK_OF_DECLARE etc. and could lead
>> to deprecating of those macros in favor of early platform drivers.
>
> This seems completely unacceptable, in that it would render new
> kernels unable to boot on existing device trees (which may be
> hard-coded in rom on existing devices).
>

Just ot make it clear: by deprecating I meant not accepting any new
users, not blindly replacing the current ones.

Thanks,
Bart

  reply	other threads:[~2018-04-25  9:33 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-24 17:30 Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 01/11] platform: early: provide early_platform_add_device() Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 02/11] platform: provide early_platform_driver_register_probe_all() Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 03/11] platform: make support for early platform devices conditional Bartosz Golaszewski
2018-04-24 19:31   ` Randy Dunlap
2018-04-25 14:02   ` Rich Felker
2018-04-24 17:30 ` [PATCH 04/11] of: platform: use pdev as name for vars of type struct platform_device Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 05/11] platform: use a dedicated list_head for early devices Bartosz Golaszewski
2018-04-26  4:27   ` kbuild test robot
2018-04-24 17:30 ` [PATCH 06/11] of: provide for_each_compatible_child_node() Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 07/11] dt-bindings: add bindings for early devices Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 08/11] of: platform: provide of_early_platform_populate() Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 09/11] platform: provide early_platform_driver() Bartosz Golaszewski
2018-04-24 17:30 ` [PATCH 10/11] of: platform: provide of_early_platform_probe() Bartosz Golaszewski
2018-04-26  3:46   ` kbuild test robot
2018-04-24 17:30 ` [PATCH 11/11] misc: implement a dummy early platform driver Bartosz Golaszewski
2018-04-24 17:55 ` [PATCH 00/11] platform: device tree support for early platform drivers Mark Rutland
2018-04-24 17:59   ` Rich Felker
2018-04-24 17:57 ` Rich Felker
2018-04-25  9:33   ` Bartosz Golaszewski [this message]
2018-04-24 18:19 ` Robin Murphy
2018-04-24 19:39 ` Rob Herring

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