linux-kernel - Re: [PATCH 2/3] PCI: Add quirks for devices found on Cavium ThunderX SoCs.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <55FCB3AC.8080709@caviumnetworks.com>
Date:	Fri, 18 Sep 2015 18:00:28 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	David Daney <ddaney.cavm@...il.com>,
	<linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	<linux-pci@...r.kernel.org>, Will Deacon <will.deacon@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	<devicetree@...r.kernel.org>, Marc Zyngier <marc.zyngier@....com>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 2/3] PCI: Add quirks for devices found on Cavium ThunderX
 SoCs.

On 09/18/2015 12:45 PM, Arnd Bergmann wrote:
> On Friday 18 September 2015 10:00:32 David Daney wrote:
>> On 09/18/2015 12:19 AM, Arnd Bergmann wrote:
>>> On Thursday 17 September 2015 15:41:33 David Daney wrote:
>>>> From: David Daney <david.daney@...ium.com>
>>>>
>>>> The on-chip devices all have fixed bars.  So, fix them up.
>>>>
>>>> Signed-off-by: David Daney <david.daney@...ium.com>
>>>>
>>>
>>> You should be able to just mark the BARs as fixed in DT

I think we can switch to PCI_PROBE_ONLY, and have all non-fixed BAR 
devices configured by firmware.  This may significantly simplify any 
quirks required in the kernel.


>>
>> In the case of ACPI, there is no DT.  So we would need a different
>> solution for ACPI.  What would you recommend for ACPI?
>
> I would expect that this does not matter at all on ACPI, because
> the devices that need it are not hot-plugged, and all boot-time
> devices are probed by the firmware: the ACPI PCI implementation
> does not reassign any BARs, except for the hotplug case.
>
>> Also, can you point me to the OF device tree specification where it
>> tells how to specify PCI BAR addresses, I would especially be interested
>> in knowing how to specify fixed SRIOV BAR addresses in the device tree.
>
> This is the 'n' bit mentioned sections 2.1.3 and 2.2.1.1 of the
> PCI binding. When it is set, the OS is not supposed to try to
> reassign the BAR even on machines that otherwise do a complete
> rescan.
>
> The PCI binding traditionally requires you to list all PCI devices
> in DT, Linux as an extension (for the flattened DT format) allows
> leaving out the devices, but in this case you probably need to
> list every device that has a fixed BAR.
>
>> Yes, it is a bit of a hack.  That is why I put it in its own file, and
>> only try to hack up PCI devices that exactly match the vendor and device
>> ids that need fixing.
>>
>> IMHO, putting infrastructure into drivers/pci/probe.c, et al. to handle
>> this would be much more intrusive.
>
> My guess is that it's already there, but even if it's not, this is a
> generic well-defined case that has a standardized binding, and we should
> implement that.
>
>> For the record:  The PCI Enhanced Allocation (EA) capability (approved
>> by PCI SIG on 23 October 2014) is the proper way to handle this going
>> forward.  However, this is not yet implemented in the SoCs that this
>> patch addresses.  Our plan is to implement the EA capability in the core
>> PCI code, so that we do not need to keep adding devices to this fixup code.
>
> Good, but still this should only be required for the embedded case where
> you don't have a firmware to probe the bus.
>
> 	Arnd
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/