From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Rob Herring <robh@kernel.org>, Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Linus Walleij <linus.walleij@linaro.org>,
Alexander Graf <agraf@suse.de>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Kevin Hilman <khilman@kernel.org>,
Ulf Hansson <ulf.hansson@linaro.org>,
Joerg Roedel <joro@8bytes.org>,
Robin Murphy <robin.murphy@arm.com>,
Mark Brown <broonie@kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
boot-architecture@lists.linaro.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/8] driver core: make deferring probe after init optional
Date: Thu, 24 May 2018 15:28:55 -0700 [thread overview]
Message-ID: <20180524222855.GD14924@minitux> (raw)
In-Reply-To: <20180524175024.19874-2-robh@kernel.org>
On Thu 24 May 10:50 PDT 2018, Rob Herring wrote:
> Deferred probe will currently wait forever on dependent devices to probe,
> but sometimes a driver will never exist. It's also not always critical for
> a driver to exist. Platforms can rely on default configuration from the
> bootloader or reset defaults for things such as pinctrl and power domains.
> This is often the case with initial platform support until various drivers
> get enabled. There's at least 2 scenarios where deferred probe can render
> a platform broken. Both involve using a DT which has more devices and
> dependencies than the kernel supports. The 1st case is a driver may be
> disabled in the kernel config. The 2nd case is the kernel version may
> simply not have the dependent driver. This can happen if using a newer DT
> (provided by firmware perhaps) with a stable kernel version.
>
> Subsystems or drivers may opt-in to this behavior by calling
> driver_deferred_probe_check_init_done() instead of just returning
> -EPROBE_DEFER. They may use additional information from DT or kernel's
> config to decide whether to continue to defer probe or not.
>
For builtin drivers this still looks reasonable.
But I would like to have an additional clarification here stating that
drivers that might be targeted by this query must not be compiled as
modules.
And I would prefer to see an ack from e.g. Arnd that arm-soc is okay
that we drop "tristate" on drivers affected by this; e.g. if we put this
in the pinctrl core then all pinctrl drivers should be "bool" and so
should any i2c, ssbi and spmi buses and drivers be.
Regards,
Bjorn
> Cc: Alexander Graf <agraf@suse.de>
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
> drivers/base/dd.c | 17 +++++++++++++++++
> include/linux/device.h | 2 ++
> 2 files changed, 19 insertions(+)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index c9f54089429b..d6034718da6f 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -226,6 +226,16 @@ void device_unblock_probing(void)
> driver_deferred_probe_trigger();
> }
>
> +int driver_deferred_probe_check_init_done(struct device *dev, bool optional)
> +{
> + if (optional && initcalls_done) {
> + dev_WARN(dev, "ignoring dependency for device, assuming no driver");
> + return -ENODEV;
> + }
> +
> + return -EPROBE_DEFER;
> +}
> +
> /**
> * deferred_probe_initcall() - Enable probing of deferred devices
> *
> @@ -240,6 +250,13 @@ static int deferred_probe_initcall(void)
> /* Sort as many dependencies as possible before exiting initcalls */
> flush_work(&deferred_probe_work);
> initcalls_done = true;
> +
> + /*
> + * Trigger deferred probe again, this time we won't defer anything
> + * that is optional
> + */
> + driver_deferred_probe_trigger();
> + flush_work(&deferred_probe_work);
> return 0;
> }
> late_initcall(deferred_probe_initcall);
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 477956990f5e..f3dafd44c285 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -334,6 +334,8 @@ struct device *driver_find_device(struct device_driver *drv,
> struct device *start, void *data,
> int (*match)(struct device *dev, void *data));
>
> +int driver_deferred_probe_check_init_done(struct device *dev, bool optional);
> +
> /**
> * struct subsys_interface - interfaces to device functions
> * @name: name of the device function
> --
> 2.17.0
>
next prev parent reply other threads:[~2018-05-24 22:29 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-24 17:50 [PATCH v2 0/8] Make deferring probe forever optional Rob Herring
2018-05-24 17:50 ` [PATCH v2 1/8] driver core: make deferring probe after init optional Rob Herring
2018-05-24 18:18 ` Mark Brown
2018-05-24 20:25 ` Rob Herring
2018-05-25 11:47 ` Robin Murphy
2018-05-29 5:12 ` Frank Rowand
2018-05-29 14:46 ` Rob Herring
2018-05-24 18:56 ` Greg Kroah-Hartman
2018-05-24 19:42 ` Rob Herring
2018-05-24 19:00 ` Greg Kroah-Hartman
2018-05-24 20:57 ` Rob Herring
2018-05-25 12:20 ` Robin Murphy
2018-05-25 17:35 ` Rob Herring
2018-05-24 22:28 ` Bjorn Andersson [this message]
2018-05-24 23:47 ` Rob Herring
2018-05-24 17:50 ` [PATCH v2 2/8] driver core: add a deferred probe timeout Rob Herring
2018-05-24 19:01 ` Greg Kroah-Hartman
2018-05-24 19:45 ` Rob Herring
2018-05-24 19:51 ` Greg Kroah-Hartman
2018-05-24 17:50 ` [PATCH v2 3/8] dt-bindings: pinctrl: add a 'pinctrl-use-default' property Rob Herring
2018-05-24 17:50 ` [PATCH v2 4/8] arm: dts: bcm283x: mark the UART pin muxing nodes with pinctrl-use-default Rob Herring
2018-05-24 17:50 ` [PATCH v2 5/8] pinctrl: optionally stop deferring probe at end of initcalls Rob Herring
2018-05-30 7:00 ` Linus Walleij
2018-05-24 17:50 ` [PATCH v2 6/8] iommu: Stop " Rob Herring
2018-05-24 17:50 ` [PATCH v2 7/8] iommu: Remove IOMMU_OF_DECLARE Rob Herring
2018-05-25 11:31 ` Will Deacon
2018-05-28 6:53 ` Marek Szyprowski
2018-05-24 17:50 ` [PATCH v2 8/8] PM / Domains: Stop deferring probe at the end of initcall Rob Herring
2018-05-29 11:48 ` [PATCH v2 0/8] Make deferring probe forever optional Joerg Roedel
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