linux-kernel - Re: [PATCH v10 08/10] OF: PCI: Add support for parsing PCI host bridge resources from DT

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Message-ID: <20140910165347.GJ27864@e106497-lin.cambridge.arm.com>
Date:	Wed, 10 Sep 2014 17:53:47 +0100
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>,
	Rob Herring <robh+dt@...nel.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Russell King <linux@....linux.org.uk>,
	linux-pci <linux-pci@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	linux-arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>
Subject: Re: [PATCH v10 08/10] OF: PCI: Add support for parsing PCI host
 bridge resources from DT

On Wed, Sep 10, 2014 at 05:37:47PM +0100, Lorenzo Pieralisi wrote:
> On Wed, Sep 10, 2014 at 04:32:33PM +0100, Liviu Dudau wrote:
> 
> [...]
> 
> > > > > > +		/*
> > > > > > +		 * If we failed translation or got a zero-sized region
> > > > > > +		 * then skip this range
> > > > > > +		 */
> > > > > > +		if (range.cpu_addr == OF_BAD_ADDR || range.size == 0)
> > > > > > +			continue;
> > > > > > +
> > > > > > +		res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> > > > > > +		if (!res) {
> > > > > > +			err = -ENOMEM;
> > > > > > +			goto parse_failed;
> > > > > > +		}
> > > > > > +
> > > > > > +		err = of_pci_range_to_resource(&range, dev, res);
> > > > > > +		if (err) {
> > > > > > +			kfree(res);
> > > > > 
> > > > > You might want to add a label to free res to make things more uniform.
> > 
> > Sorry, not following you. How would a label help here?
> 
> It was just a suggestion so ignore it if you do not think it is cleaner.
> It is to make code more uniform and undo operations in one place instead of
> doing it piecemeal (you kfree the res here and jump to complete the clean-up,
> whereas you might want to add a different label and a different goto
> destination and carry out the kfree there).

But that kfree is the only done once, while the pci_free_resource_list() is
done twice.

> 
> I do not mind either, it is just what I noticed.
> 
> > > > > > +			goto parse_failed;
> > > > > > +		}
> > > > > > +
> > > > > > +		if (resource_type(res) == IORESOURCE_IO) {
> > > > > > +			if (*io_base)
> > > > > 
> > > > > You do not zero io_base in the first place so you should ask the API
> > > > > user to do that. Is 0 a valid value BTW ? If it is you've got to resort
> > > > > to something else to detect multiple IO resources.
> > 
> > No, zero is not a valid value. It is the cpu_addr value from the IO range, I'm
> > hopying that no one is crazy enough to map PCI address space at CPU address zero.
> > Thanks for spotting the lack of initialisation though, I need to fix it.
> 
> Mmm...wasn't a trick question sorry :D
> 
> PCI host bridge /pci ranges:
>    IO 0x00000000..0x0000ffff -> 0x00000000
>    More than one I/O resource converted. CPU offset for old range lost!
>      MEM 0x41000000..0x7fffffff -> 0x41000000
>      pci-host-generic 40000000.pci: PCI host bridge to bus 0000:00
>      pci_bus 0000:00: root bus resource [bu-01]
>      pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
>      pci_bus 0000:00: root bus resource [mem 0x41000000-0x7fffffff]
> 

Your DT puts the IO space at CPU address zero? Could you copy the relevant
host bridge node from DT here?

Best regards,
Liviu

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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