linux-kernel - Re: [PATCH V6 08/13] PCI: generic, thunder: update to use generic ECAM API

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Date:	Thu, 21 Apr 2016 11:28:15 +0200
From:	Tomasz Nowicki <tn@...ihalf.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Jayachandran C <jchandra@...adcom.com>,
	linux-arm-kernel@...ts.infradead.org,
	Bjorn Helgaas <helgaas@...nel.org>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>, rafael@...nel.org,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Sinan Kaya <okaya@...eaurora.org>, jiang.liu@...ux.intel.com,
	Jon Masters <jcm@...hat.com>, linaro-acpi@...ts.linaro.org,
	linux-pci@...r.kernel.org, Liviu.Dudau@....com,
	David Daney <ddaney@...iumnetworks.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	robert.richter@...iumnetworks.com, Suravee.Suthikulpanit@....com,
	msalter@...hat.com, Wangyijing <wangyijing@...wei.com>,
	Marcin Wojtas <mw@...ihalf.com>
Subject: Re: [PATCH V6 08/13] PCI: generic, thunder: update to use generic
 ECAM API



On 19.04.2016 15:06, Arnd Bergmann wrote:
> On Monday 18 April 2016 21:31:54 Tomasz Nowicki wrote:
>>
>> Basically the whole content of pci-thunder-ecam.c and pci-thunder-pem.c.
>>
>> pci-thunder-ecam.c contains config space accessors. Similar for
>> pci-thunder-pem.c but it also has extra init call (it is now called
>> thunder_pem_init) which finds and maps related registers.
>
> They seem to do much more than just override the accessors, they actually
> change the contents of the config space as well. Is that really necessary
> on ACPI based systems as well?

Yes, the pci-thunder-ecam.c accessors are meant to emulate config space 
capabilities. They are necessary to synthesize EA capabilities (fixed 
PCI BARs), it wont work without this, for ACPI boot as well.

>
> Another idea: how about moving all of this logic into ACPI and calling
> some AML method to access the config space if the devices are that
> far out of spec.

Do you mean Linux specific way to call non-standard config space 
accessors? Then non-standard accessors are going to AML methods which 
are called from common code which handles quirks via unified API ?

Thanks,
Tomasz