linux-kernel - Re: [PATCH v11 1/6] PCI: designware: move calculation of bus addresses to DRA7xx

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Date:	Thu, 22 Oct 2015 11:35:34 -0500
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Gabriele Paoloni <gabriele.paoloni@...wei.com>
Cc:	"Wangzhou (B)" <wangzhou1@...ilicon.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"jingoohan1@...il.com" <jingoohan1@...il.com>,
	"pratyush.anand@...il.com" <pratyush.anand@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"thomas.petazzoni@...e-electrons.com" 
	<thomas.petazzoni@...e-electrons.com>,
	"lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
	"james.morse@....com" <james.morse@....com>,
	"Liviu.Dudau@....com" <Liviu.Dudau@....com>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"robh@...nel.org" <robh@...nel.org>,
	"gabriel.fernandez@...aro.org" <gabriel.fernandez@...aro.org>,
	"Minghuan.Lian@...escale.com" <Minghuan.Lian@...escale.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	zhangjukuo <zhangjukuo@...wei.com>,
	qiuzhenfa <qiuzhenfa@...ilicon.com>,
	"liudongdong (C)" <liudongdong3@...wei.com>,
	qiujiang <qiujiang@...wei.com>,
	"xuwei (O)" <xuwei5@...ilicon.com>,
	"Liguozhu (Kenneth)" <liguozhu@...ilicon.com>
Subject: Re: [PATCH v11 1/6] PCI: designware: move calculation of bus
 addresses to DRA7xx

Hi Gabriele,

On Thu, Oct 22, 2015 at 07:21:41AM +0000, Gabriele Paoloni wrote:
> > -----Original Message-----
> > From: Bjorn Helgaas [mailto:helgaas@...nel.org]

> > >  #define	PCIECTRL_DRA7XX_CONF_PHY_CS			0x010C
> > >  #define	LINK_UP						BIT(16)
> > > +#define	CPU_TO_BUS_ADDR					0x0FFFFFFF
> > 
> > "CPU_TO_BUS_ADDR" is a very generic name.  Since you do have DRA7XX in
> > other #defines and static symbols in this file, maybe it could be DRA7XX to
> > make it obvious that it only applies here?
> 
> Ok will change to DRA7XX_CPU_TO_BUS_ADRR in v12
> ..

> > > +	if (pp->io_mod_base)
> > > +		pp->io_mod_base &= CPU_TO_BUS_ADDR;
> > 
> > These are equivalent to
> > 
> >   pp->io_mod_base &= CPU_TO_BUS_ADDR;
> > 
> > (You don't need to test whether they're zero first.)
> 
> Yes agreed, will change in v12
> ...

> > >  	cfg_res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "config");
> > > @@ -415,8 +411,7 @@ int dw_pcie_host_init(struct pcie_port *pp)
> > >  			pp->io_base = range.cpu_addr;
> > >
> > >  			/* Find the untranslated IO space address */
> > > -			pp->io_mod_base = of_read_number(parser.range -
> > > -							 parser.np + na, ns);
> > > +			pp->io_mod_base = range.cpu_addr;
> > 
> > So apparently
> > 
> >   "of_read_number() == range.cpu_addr & CPU_TO_BUS_ADDR" on DRA7xx
> >   "of_read_number() == range.cpu_addr" everywhere else?
> 
> Yes correct
> 
> > Is that right?  Is that a valid assumption, i.e., are we assuming
> > anything about DTs in the field that we shouldn't?
> 
> Before I wrote a patch that was generic to accommodate intermediate level
> of translation between PCI_addr -> BUS_addr -> CPU_addr
> 
> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/360922.html
> 
> After discussion we agreed to solve it with a bitmask rather than adding
> a field to of_pci_range to make it generic.
> The bitmask only applies to DRA7xx

I haven't gotten all the way through this series yet, but don't bother with
a v12 just for these minor changes.  I can easily fix them up when applying
it.

Bjorn
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