Subject: Re: [PATCH V6 08/13] PCI: generic, thunder: update to use generic
 ECAM API
To: Arnd Bergmann <arnd@arndb.de>
References: <1460740008-19489-1-git-send-email-tn@semihalf.com>
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Cc: Jayachandran C <jchandra@broadcom.com>,
        linux-arm-kernel@lists.infradead.org,
        Bjorn Helgaas <helgaas@kernel.org>, Will Deacon <will.deacon@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>, rafael@kernel.org,
        Hanjun Guo <hanjun.guo@linaro.org>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>,
        Sinan Kaya <okaya@codeaurora.org>, jiang.liu@linux.intel.com,
        Jon Masters <jcm@redhat.com>, linaro-acpi@lists.linaro.org,
        linux-pci@vger.kernel.org, Liviu.Dudau@arm.com,
        David Daney <ddaney@caviumnetworks.com>, linux-kernel@vger.kernel.org,
        linux-acpi@vger.kernel.org, robert.richter@caviumnetworks.com,
        Suravee.Suthikulpanit@amd.com, msalter@redhat.com,
        Wangyijing <wangyijing@huawei.com>, Marcin Wojtas <mw@semihalf.com>
From: Tomasz Nowicki <tn@semihalf.com>
Message-ID: <57189D2F.9070802@semihalf.com>
Date: Thu, 21 Apr 2016 11:28:15 +0200
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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