linux-kernel - Re: [PATCH V2 22/23] pci, acpi: Match PCI config space accessors against platfrom specific quirks.

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Message-ID: <567923D2.2010202@semihalf.com>
Date:	Tue, 22 Dec 2015 11:20:02 +0100
From:	Tomasz Nowicki <tn@...ihalf.com>
To:	Gabriele Paoloni <gabriele.paoloni@...wei.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"will.deacon@....com" <will.deacon@....com>,
	"catalin.marinas@....com" <catalin.marinas@....com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"hanjun.guo@...aro.org" <hanjun.guo@...aro.org>,
	"Lorenzo.Pieralisi@....com" <Lorenzo.Pieralisi@....com>,
	"okaya@...eaurora.org" <okaya@...eaurora.org>,
	"jiang.liu@...ux.intel.com" <jiang.liu@...ux.intel.com>,
	"Stefano.Stabellini@...citrix.com" <Stefano.Stabellini@...citrix.com>
Cc:	"robert.richter@...iumnetworks.com" 
	<robert.richter@...iumnetworks.com>,
	"mw@...ihalf.com" <mw@...ihalf.com>,
	"Liviu.Dudau@....com" <Liviu.Dudau@....com>,
	"ddaney@...iumnetworks.com" <ddaney@...iumnetworks.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Wangyijing <wangyijing@...wei.com>,
	"Suravee.Suthikulpanit@....com" <Suravee.Suthikulpanit@....com>,
	"msalter@...hat.com" <msalter@...hat.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	"jchandra@...adcom.com" <jchandra@...adcom.com>,
	"jcm@...hat.com" <jcm@...hat.com>
Subject: Re: [PATCH V2 22/23] pci, acpi: Match PCI config space accessors
 against platfrom specific quirks.

On 21.12.2015 12:47, Gabriele Paoloni wrote:
> 2) In the quirk mechanism you proposed, I see that the callback function
>     allows to do some preparation work for the host bridge. For example in
>     Hisilicon hip05 case we would need to read some values from the ACPI
>     table (see acpi_pci_root_hisi_add() function in
>     https://lkml.org/lkml/2015/12/3/426).
>     I am quite new to ACPI and I wonder if it is OK to add such "Packages"
>     to the  PCI host bridge ACPI device...or maybe we need to declare a new
>     one...?

I may miss sth so please correct me in that case.

https://lkml.org/lkml/2015/12/3/426 shows that you need special handling 
for root->secondary.start bus number only, right? So how about creating 
special MCFG region <rc-base:rc-base+rc-size> only for <segment,bus>. 
Like that:

[0008]                       Base Address : <rc-base>
[0002]               Segment Group Number : <segment>
[0001]                   Start Bus Number : <root->secondary.start>
[0001]                     End Bus Number : <root->secondary.start>
[0004]                           Reserved : 00000000


static const struct dmi_system_id hisi_quirk[] = {
	{
		.ident = "HiSi...",
		.matches = {
			DMI_MATCH(<whatever you need to match your platform>),
		},
	},
	{ }
};

static struct pci_ops hisi_ecam_pci_ops = {
	.map_bus = pci_mcfg_dev_base,
	.read = hisi_pcie_cfg_read,
	.write = hisi_pcie_cfg_write,
};

DECLARE_ACPI_MCFG_FIXUP(hisi_quirk, &hisi_ecam_pci_ops,
			<segment>, <bus>);

With above code you can use your custom PCI config accessor only for 
that region.

Let me know if that is not enough for you.

Tomasz
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