linux-kernel - Re: [PATCH 2/3] PCI: designware: use untranslated address while programming ATU

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Message-ID: <20140626063336.GA6166@pratyush-vbox>
Date:	Thu, 26 Jun 2014 12:03:37 +0530
From:	Pratyush Anand <pratyush.anand@...com>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Pratyush Anand <pratyush.anand@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mohit KUMAR DCG <Mohit.KUMAR@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Marek Vasut <marex@...x.de>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 2/3] PCI: designware: use untranslated address while
 programming ATU

Hi Kishon,

On Thu, Jun 26, 2014 at 02:10:02PM +0800, Kishon Vijay Abraham I wrote:
> Hi Pratyush,
> 
> On Thursday 26 June 2014 11:07 AM, Pratyush Anand wrote:
> > Hi Kishon,
> > 
> >  Few things, if you can help me to understand:
> > 
> > On Wed, Jun 25, 2014 at 11:26 PM, Kishon Vijay Abraham I <kishon@...com> wrote:
> >> In DRA7, the cpu sees 32bit address, but the pcie controller can see only 28bit
> >> address. So whenever the cpu issues a read/write request, the 4 most
> >> significant bits are used by L3 to determine the target controller.
> >> For example, the cpu reserves 0x2000_0000 - 0x2FFF_FFFF for PCIe controller but
> >> the PCIe controller will see only (0x000_0000 - 0xFFF_FFF). So for programming
> >> the outbound translation window the *base* should be programmed as 0x000_0000.
> >> Whenever we try to write to say 0x2000_0000, it will be translated to whatever
> >> we have programmed in the translation window with base as 0x000_0000.
> >>
> >> This is needed when the dt node is modelled something like below
> >> axi {
> >>         compatible = "simple-bus";
> >>         #size-cells = <1>;
> >>         #address-cells = <1>;
> >>         ranges = <0x0        0x20000000 0x10000000 // 28-bit bus
> >>                   0x51000000 0x51000000 0x3000>;
> >>         pcie@...00000 {
> >>                 reg = <0x1000 0x2000>, <0x51002000 0x14c>, <0x51000000 0x2000>;
> >>                 reg-names = "config", "ti_conf", "rc_dbics";
> > 
> > So for DRA7, config base which will be coming from reg property should
> > be 0x1000 and size 0x2000, no?
> 
> right. The first element in 'reg' and 'reg-names' specify exactly that.
> > 
> >>                 #address-cells = <3>;
> >>                 #size-cells = <2>;
> >>                 ranges = <0x81000000 0 0          0x03000 0 0x00010000
> > 
> > range type 0x81000000 tells that it is IO
> > 
> >>                           0x82000000 0 0x20013000 0x13000 0 0xffed000>;
> > 
> > range type 0x81000000 tells that it is mem
> > 
> > 
> >>         };
> >> };
> >>
> >> Here the CPU address for configuration space is 0x20013000 and the controller
> >> address for configuration space is 0x13000. The controller address should
> > be
> > 
> > If above understanding is correct then:
> > 
> > Aren't these addresses(0x20013000  and 0x13000) from mem space
> > instead of configuration space.
> 
> Sorry. I didn't get you. Configuration space is different from mem space and IO
> space. We specify only the configuration space in "reg", the IO space and
> memory space should be specified in ranges.
> 
> In my case
> configuration space range: 0x20001000 - 0x20002fff
> IO space range:            0x20003000 - 0x20012fff
> Mem space range:           0x20013000 - 0x2fffffff
> 
> Here only the configuration space is obtained from 'reg' and 'IO' and 'MEM'
> space is obtained from ranges.
> > 
> > If yes, then how can you get two addresses (CPU and Controller address)
> > from reg property for configuration space?
> 
> I used platform_get_resource_byname() to get CPU address and of_get_address()
> to get the untranslated controller address.

This is what I am not able to understand that how does
platform_get_resource_byname gives correct CPU address from reg =
<0x1000 0x2000>?

cfg_res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "config");

how cfg_res->start is now 0x20001000? Shouldn't cfg_res->start be
0x1000?

What am I missing?

Thanks for explaining.

~Pratyush



> Thanks
> Kishon
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