linux-kernel - Re: [RESEND: RFC PATCH 3/3] pcie: keystone: add pcie driver based on designware core driver

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Date:	Wed, 2 Apr 2014 13:23:33 -0400
From:	Murali Karicheri <m-karicheri2@...com>
To:	Andrew Murray <amurray@...edded-bits.co.uk>
CC:	Thierry Reding <thierry.reding@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Richard Zhu <r65037@...escale.com>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Jingoo Han <jg1.han@...sung.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Shilimkar, Santosh" <santosh.shilimkar@...com>,
	Mohit Kumar <mohit.kumar@...com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Shawn Guo <shawn.guo@...aro.org>
Subject: Re: [RESEND: RFC PATCH 3/3] pcie: keystone: add pcie driver based
 on designware core driver

On 4/2/2014 12:47 PM, Andrew Murray wrote:
> On 2 April 2014 16:43, Murali Karicheri <m-karicheri2@...com> wrote:
>
>> Keystone pcie driver is developed based on other dw based pcie drivers
>>
>> such as pci-exynos that uses subsys_initcall(). I am new to this list,
>>
>> probably Jingoo (copied) has some history on why we can't use module.
>> For now I will keep it as is and can be re-visited in the next revisions.
>> Also I will experiment with PCIE port driver as well.
>>
>>
>> BTW, PCIE driver currently uses Legacy or MSI IRQ. Keystone PCI has
>> a platform IRQ. Is DT based irq configuration is the appropriate way
>> to add this capability?
> As far as I am aware - the PCI standards define a particular way for
> devices to describe which interrupt will be used for things like
> hotplug, AER and PME. These interrupts are always PCI interrupts (i.e.
> MSI/MSI-X/legacy). Thus the port services code in the kernel uses
> standard configuration space accesses to determine the interrupt to
> use. Also note that it's not just the host bridge that can provide
> these services but any PCIE device, I guess in this sense a host
> bridge is treated like any other device.
>
> If my understanding is correct I don't believe the current port
> services code allows exceptions to this, i.e. to say this host bridge
> actually uses a platform IRQ for AER rather than an MSI. Though this
> may be quite useful as I suspect many host bridges provide interrupts
> for things like PME through platform IRQs rather that PCI interrupts.
>
> Does the Keystone have platform IRQs for things like AER? Is that
> because the IP makes these events available through platform IRQs in
> addition to the standard PCI means?
>
> Andrew Murray
Andrew,

Yes. Keystone PCIe hw is based on designware hw version v3.65 that 
implements
Error interrupt as a platform IRQ only (not in addition) and 
unfortunately standard
PCI means are not supported. The latter versions do support standard PCI 
means.

Murali

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