linux-kernel - Re: Purpose of pci_remap

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Message-ID: <4711052.Qi2htfK0nU@wuerfel>
Date:	Fri, 15 Jul 2016 08:55:46 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
Cc:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Liviu.Dudau@....com" <Liviu.Dudau@....com>,
	nofooter <nofooter@...inx.com>,
	"thomas.petazzoni@...e-electrons.com" 
	<thomas.petazzoni@...e-electrons.com>,
	Rongrong Zou <zourongrong@...wei.com>,
	Rongrong Zou <zourongrong@...il.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: Purpose of pci_remap_iospace

On Friday, July 15, 2016 5:21:20 AM CEST Bharat Kumar Gogada wrote:
> > On Thu, Jul 14, 2016 at 01:32:13PM +0000, Bharat Kumar Gogada wrote:
> >
> > [...]
> >
> > > Hi Lorenzo,
> > >
> > > I missed something in my device tree now I corrected it.
> > >
> > > ranges = <0x01000000 0x00000000 0xe0000000 0x00000000 0xe0000000 0
> > 0x00010000   //io
> >
> > You have not missed anything, you changed the PCI bus address at which
> > your host bridge responds to IO space and it must match your configuration.
> > At what PCI bus address your host bridge maps IO space ?
> >
> Our host bridge does not have dedicted address space mapped for IO transactions.
> For generation of IO transactions it requires some register read and write operations
> in bridge logic.
> 
> So the above PCI address does not come in to picture also, is there alternate way to handle IO
> Bars with our kind of hardware architecture.

Hisilicon has a similar thing on one of their LPC bridges, and
Rongrong Zou has implemented something for it in the past, but I
think it never got merged.

https://lkml.org/lkml/2015/12/29/154 has one version of his
proposal, not sure if that was the latest one or if something
newer exists.

	Arnd