Re: [PATCH V4] PCI: rcar: Add L1 link state fix into data abort hook

From: Marek Vasut <marek.vasut@gmail.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Wolfram Sang <wsa@the-dreams.de>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH V4] PCI: rcar: Add L1 link state fix into data abort hook
Date: Sat, 12 Dec 2020 20:10:13 +0100	[thread overview]
Message-ID: <0688fa35-74ab-91d8-7e3c-aae93439e6fd@gmail.com> (raw)
In-Reply-To: <20201208184627.GA2393103@bjorn-Precision-5520>

On 12/8/20 7:46 PM, Bjorn Helgaas wrote:

[...]

>>>> +static int __init rcar_pcie_init(void)
>>>> +{
>>>> +	if (of_find_matching_node(NULL, rcar_pcie_abort_handler_of_match)) {
>>>> +#ifdef CONFIG_ARM_LPAE
>>>> +		hook_fault_code(17, rcar_pcie_aarch32_abort_handler, SIGBUS, 0,
>>>> +				"asynchronous external abort");
>>>> +#else
>>>> +		hook_fault_code(22, rcar_pcie_aarch32_abort_handler, SIGBUS, 0,
>>>> +				"imprecise external abort");
>>>> +#endif
>>>> +	}
>>>> +
>>>> +	return platform_driver_register(&rcar_pcie_driver);
>>>> +}
>>>> +device_initcall(rcar_pcie_init);
>>>> +#else
>>>>    builtin_platform_driver(rcar_pcie_driver);
>>>> +#endif
>>>
>>> Is the device_initcall() vs builtin_platform_driver() something
>>> related to the hook_fault_code()?  What would break if this were
>>> always builtin_platform_driver()?
>>
>> rcar_pcie_init() would not be called before probe.
> 
> Sorry to be slow, but why does it need to be called before probe?
> Obviously software isn't putting the controller in D3 or enabling ASPM
> before probe.

The hook_fault_code() is marked __init, so if probe() was deferred and 
the kernel __init memory was free'd, attempt to call hook_fault_code() 
from probe would lead to a crash.