linux-kernel - Re: [PATCH v2 01/12] device: property: delay device-driver matches

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Message-ID: <CAAObsKA_B38EaS4uNaFUmpQ+Kr0Jq3CqAegLpYX=vr9e6nNgBw@mail.gmail.com>
Date:	Fri, 10 Jul 2015 13:39:48 +0200
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>, linux-acpi@...r.kernel.org,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	linux-fbdev@...r.kernel.org, linux-gpio@...r.kernel.org,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux PWM List <linux-pwm@...r.kernel.org>,
	alsa-devel@...a-project.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 01/12] device: property: delay device-driver matches

On 2 July 2015 at 01:29, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Wednesday, July 01, 2015 11:40:56 AM Tomeu Vizoso wrote:
>> Delay matches of platform devices until late_initcall, when we are sure
>> that all built-in drivers have been registered already. This is needed
>> to prevent deferred probes because of some dependencies' drivers not
>> having registered yet.
>>
>> This reduces the total amount of work that the kernel does during boot
>> because it won't try to match devices to drivers when built-in drivers
>> are still registering but also reduces some parallelism, so total boot
>> time might slightly increase or decrease depending on the platform and
>> kernel configuration.
>>
>> This change will make make possible to prevent any deferred probes once
>> devices are probed in dependency order.
>>
>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>> ---
>>
>> Changes in v2:
>> - Instead of delaying all probes until late_initcall, only delay matches
>>   of platform devices that have a firmware node attached.
>>
>>  drivers/base/property.c | 29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/drivers/base/property.c b/drivers/base/property.c
>> index 8528eb9..8ead1ba 100644
>> --- a/drivers/base/property.c
>> +++ b/drivers/base/property.c
>> @@ -16,8 +16,11 @@
>>  #include <linux/of.h>
>>  #include <linux/of_address.h>
>>  #include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>>  #include <linux/property.h>
>>
>> +static bool fwnode_match_enable = false;
>> +
>>  /**
>>   * device_add_property_set - Add a collection of properties to a device object.
>>   * @dev: Device to add properties to.
>> @@ -604,6 +607,15 @@ EXPORT_SYMBOL_GPL(fwnode_is_compatible);
>>  bool fwnode_driver_match_device(struct device *dev,
>>                               const struct device_driver *drv)
>>  {
>> +     /*
>> +      * Delay matches of platform devices until late_initcall, when we are
>> +      * sure that all built-in drivers have been registered already. This
>> +      * is needed to prevent deferred probes because of some drivers
>> +      * not having registered yet.
>> +      */
>> +     if(dev->bus == &platform_bus_type && !fwnode_match_enable)
>> +             return false;
>
> I'm not particularly enthusiastic about referring to specific bus types in
> generic code like that.

Agreed.

> What about having a special version of fwnode_driver_match_device() specifically
> for the platform bus type that will do the check?

Have moved all this code to base/platform.c instead, as I don't see
any reason to have it in property.c.

Thanks,

Tomeu

>> +
>>       if (is_of_node(dev->fwnode))
>>               return of_driver_match_device(dev, drv);
>>       else if (is_acpi_node(dev->fwnode))
>> @@ -612,3 +624,20 @@ bool fwnode_driver_match_device(struct device *dev,
>>       return false;
>>  }
>>  EXPORT_SYMBOL_GPL(fwnode_driver_match_device);
>> +
>> +static int __device_attach(struct device *dev, void *data)
>> +{
>> +     device_initial_probe(dev);
>> +
>> +     return 0;
>> +}
>> +
>> +static int fwnode_match_initcall(void)
>> +{
>> +     fwnode_match_enable = true;
>> +
>> +     bus_for_each_dev(&platform_bus_type, NULL, NULL, __device_attach);
>> +
>> +     return 0;
>> +}
>> +late_initcall(fwnode_match_initcall);
>>
>
> --
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.
> --
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