linux-kernel - Re: [RFC PATCH 03/12] pci: host: pcie-designware: Use *base-mask* for configuring the iATU

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Date:	Thu, 27 Mar 2014 18:32:11 +0100
From:	Marek Vasut <marex@...x.de>
To:	Jingoo Han <jg1.han@...sung.com>
Cc:	"'Kishon Vijay Abraham I'" <kishon@...com>,
	"'Mohit Kumar'" <mohit.kumar@...com>,
	"'Pratyush Anand'" <pratyush.anand@...com>,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-omap@...r.kernel.org, linux-pci@...r.kernel.org,
	bhelgaas@...gle.com, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, rob@...dley.net, linux@....linux.org.uk,
	tony@...mide.com, rnayak@...com, paul@...an.com,
	"'Richard Zhu'" <r65037@...escale.com>
Subject: Re: [RFC PATCH 03/12] pci: host: pcie-designware: Use *base-mask* for configuring the iATU

On Thursday, March 27, 2014 at 12:45:01 PM, Jingoo Han wrote:
> On Wednesday, March 26, 2014 10:58 PM, Kishon Vijay Abraham I 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.
> > 
> > Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> 
> (+cc Pratyush Anand, Marek Vasut, Richard Zhu)

Thanks.

> Acked-by: Jingoo Han <jg1.han@...sung.com>

This patch has no impact on MX6, the mask on MX6 is ~0 . A few comments below 
...
[...]

> > diff --git a/drivers/pci/host/pcie-designware.c
> > b/drivers/pci/host/pcie-designware.c index 17ce88f..98b661c 100644
> > --- a/drivers/pci/host/pcie-designware.c
> > +++ b/drivers/pci/host/pcie-designware.c
> > @@ -464,6 +464,9 @@ int __init dw_pcie_host_init(struct pcie_port *pp)
> > 
> >  		return -EINVAL;
> >  	
> >  	}
> > 
> > +	if (of_property_read_u64(np, "base-mask", &pp->base_mask))
> > +		pp->base_mask = ~(0x0ULL);

You can just use ~0x0ULL without the () I believe.

[...]

> > diff --git a/drivers/pci/host/pcie-designware.h
> > b/drivers/pci/host/pcie-designware.h index 3063b35..3fa12a6 100644
> > --- a/drivers/pci/host/pcie-designware.h
> > +++ b/drivers/pci/host/pcie-designware.h
> > @@ -35,6 +35,7 @@ struct pcie_port {
> > 
> >  	struct device		*dev;
> >  	u8			root_bus_nr;
> >  	void __iomem		*dbi_base;
> > 
> > +	u64			base_mask;
> > 
> >  	u64			cfg0_base;
> >  	void __iomem		*va_cfg0_base;
> >  	u64			cfg1_base;

This structure contains a lot of slop, check [1] please. We really should be 
more careful about the structures. I think a separate patch to clean this up 
would be fine though.

[1] http://www.catb.org/esr/structure-packing/
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