linux-kernel - Re: [Patch v4 0/8] Consolidate ACPI PCI root common code into ACPI core

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Message-ID: <556FF0AD.6000901@linaro.org>
Date:	Thu, 04 Jun 2015 14:31:09 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Jiang Liu <jiang.liu@...ux.intel.com>, Al Stone <ahs3@...hat.com>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Marc Zyngier <marc.zyngier@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Yijing Wang <wangyijing@...wei.com>
CC:	Lv Zheng <lv.zheng@...el.com>,
	"lenb @ kernel . org" <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, "x86 @ kernel . org" <x86@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	Mark Salter <msalter@...hat.com>
Subject: Re: [Patch v4 0/8] Consolidate ACPI PCI root common code into ACPI
 core

Hi Jiang,

On 2015年06月04日 09:54, Jiang Liu wrote:
> On 2015/6/4 4:27, Al Stone wrote:
>> On 06/02/2015 12:12 AM, Jiang Liu wrote:
>>> This patch set consolidates common code to support ACPI PCI root on x86
>>> and IA64 platforms into ACPI core, to reproduce duplicated code and
>>> simplify maintenance. And a patch set based on this to support ACPI based
>>> PCIe host bridge on ARM64 has been posted at:
>>
>> Link is missing (or it's a typo of some flavor).
> HI Al,
> 	Sorry, I missed the link. It has been posted at:
> https://lkml.org/lkml/2015/5/26/207

I failed to get io resources for PCI hostbridge  when I was testing PCI
on ARM64 QEMU, I debugged this for quite a while, and finally found out
that ACPI resource parsing for IO is not suitable for ARM64, because io
space for x86 is 64K, but 16M for ARM64.

This issue is only found when the firmware representing the io resource
using the type ACPI_RESOURCE_TYPE_ADDRESS32, so the io address will
greater than 64k.

In drivers/acpi/resource.c:

static void acpi_dev_ioresource_flags(struct resource *res, u64 len,
                                       u8 io_decode, u8 translation_type)
{
         res->flags = IORESOURCE_IO;

[...]

         if (res->end >= 0x10003)
                 res->flags |= IORESOURCE_DISABLED | IORESOURCE_UNSET;

[...]
}

so the code will filter out res->end >= 0x10003, and in my case, it will
more than 64K, so we can't get the IO resources.

I got a question, why we use if (res->end >= 0x10003) here?
I mean 64k will be 0x10000, and in that case, we should use
if (res->end >= 0x10000) here, not 0x10003, any history behind that?

This is not the problem of this patch set, but need updating
the core ACPI resource parsing code, I'm working on that. I'm
just wondering there is no special IO space on IA64, how this works
on IA64?

Thanks
Hanjun
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