linux-kernel - Re: [PATCHv2 1/2] pci: spear: Use platform_driver_probe instead of platform_driver

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Message-ID: <CAJs94EYNs9+Ph3EXZLPEepWJxU_ivXp=Tifq=LkJZ3mwk1fG3g@mail.gmail.com>
Date:	Thu, 12 Feb 2015 13:07:36 +0400
From:	"Matwey V. Kornilov" <matwey@....msu.ru>
To:	Stanimir Varbanov <svarbanov@...sol.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mohit KUMAR <mohit.kumar@...com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCHv2 1/2] pci: spear: Use platform_driver_probe instead of platform_driver_register

2015-02-11 12:19 GMT+03:00 Stanimir Varbanov <svarbanov@...sol.com>:
> please don't top posting.
>
> On 02/11/2015 10:38 AM, Matwey V. Kornilov wrote:
>>
>> It sounds reasonable, but does current implementation support deferring?
>
>
> yes, it uses deferred probe see devm_phy_get() and devm_clk_get() calls in
> .probe and how the returned values are checked.
>
>> Struct  spear13xx_pcie_driver just dissapears from memory after init.
>
>
> IMO this is expected because spear13xx_pcie_driver is annotated as
> __initdata.

The question was how deferred probe had been expected to work? When
probe has been deferred at first attempt, then second attempt
performed after init section, so proble() function must be available,
but it is not. Isn't it?

>
> The proper solution was pointed by Kumar below, but we also need to remove
> the __init from dw_pcie_host_init() which is called from driver .probe.
>
>> 11.02.2015 11:18 пользователь "Stanimir Varbanov" <svarbanov@...sol.com>
>> написал:
>>
>>> Hi,
>>>
>>> On 02/11/2015 05:35 AM, Viresh Kumar wrote:
>>>
>>>> On 11 February 2015 at 00:31, Matwey V. Kornilov <matwey@....msu.ru>
>>>> wrote:
>>>>
>>>>> Use platform_driver_probe instead of platform_driver_register
>>>>> because the former allows us to use probe function placed into __init
>>>>> section
>>>>> and the driver itself is not support hotplugging (yet?).
>>>>>
>>>>> Signed-off-by: Matwey V. Kornilov <matwey@....msu.ru>
>>>>> ---
>>>>> Changes from v1:
>>>>>    - Use platform_driver_probe instead of platform_driver_register to
>>>>> make linker happy.ven after it is used
>>>>>
>>>>>
>>>>>    drivers/pci/host/pcie-spear13xx.c | 3 +--
>>>>>    1 file changed, 1 insertion(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/pci/host/pcie-spear13xx.c b/drivers/pci/host/pcie-
>>>>> spear13xx.c
>>>>> index 866465f..51e1344 100644
>>>>> --- a/drivers/pci/host/pcie-spear13xx.c
>>>>> +++ b/drivers/pci/host/pcie-spear13xx.c
>>>>> @@ -371,7 +371,6 @@ static const struct of_device_id
>>>>> spear13xx_pcie_of_match[] = {
>>>>>    MODULE_DEVICE_TABLE(of, spear13xx_pcie_of_match);
>>>>>
>>>>>    static struct platform_driver spear13xx_pcie_driver __initdata = {
>>>>> -       .probe          = spear13xx_pcie_probe,
>>>>>           .driver = {
>>>>>                   .name   = "spear-pcie",
>>>>>                   .of_match_table = of_match_ptr(spear13xx_pcie_
>>>>> of_match),
>>>>> @@ -382,7 +381,7 @@ static struct platform_driver spear13xx_pcie_driver
>>>>> __initdata = {
>>>>>
>>>>>    static int __init spear13xx_pcie_init(void)
>>>>>    {
>>>>> -       return platform_driver_register(&spear13xx_pcie_driver);
>>>>> +       return platform_driver_probe(&spear13xx_pcie_driver,
>>>>> spear13xx_pcie_probe);
>>>>>    }
>>>>>    module_init(spear13xx_pcie_init);
>>>>>
>>>>
>>>> The problem here is that the driver is never registered. And we might
>>>> never
>>>> see it in sysfs. Probably a better solution would be to just remove all
>>>> __init
>>>> parts from this driver. Let it take space even after it is used. And
>>>> don't care
>>>> about it.
>>>>
>>>> Sorry was busy in a conference and couldn't reply to your earlier mail
>>>> on
>>>> this.
>>>>
>>>
>>> Using platform_driver_probe() prevents deferred probe which is problem
>>> because you get phy, clocks from probe, and these calls could return
>>> EPROBE_DEFFER.
>>>
>>> Also dw_pcie_host_init() called from spear13xx_add_pcie_port() is
>>> annotated as __init. I wanted send a patch which removes __init from
>>> dw_pcie_host_init() but I haven't time, yet.
>>>
>>> regards,
>>> Stan
>>>
>>>
>>
>



-- 
With best regards,
Matwey V. Kornilov.
Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia
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