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Message-ID: <20140317134103.GD6457@e106497-lin.cambridge.arm.com>
Date: Mon, 17 Mar 2014 13:41:03 +0000
From: Liviu Dudau <Liviu.Dudau@....com>
To: Arnd Bergmann <arnd@...db.de>
Cc: linux-pci <linux-pci@...r.kernel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Catalin Marinas <Catalin.Marinas@....com>,
Will Deacon <Will.Deacon@....com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linaro-kernel <linaro-kernel@...ts.linaro.org>,
LKML <linux-kernel@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
LAKML <linux-arm-kernel@...ts.infradead.org>,
Tanmay Inamdar <tinamdar@....com>,
Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH v7 2/6] pci: OF: Fix the conversion of IO ranges into IO
resources.
On Fri, Mar 14, 2014 at 07:16:10PM +0000, Arnd Bergmann wrote:
> On Friday 14 March 2014, Liviu Dudau wrote:
> > On Fri, Mar 14, 2014 at 06:46:23PM +0000, Arnd Bergmann wrote:
> > > On Friday 14 March 2014, Liviu Dudau wrote:
> > >
> > > > +int of_pci_range_to_resource(struct of_pci_range *range,
> > > > + struct device_node *np, struct resource *res)
> > > > +{
> > > > + res->flags = range->flags;
> > > > + res->parent = res->child = res->sibling = NULL;
> > > > + res->name = np->full_name;
> > > > +
> > > > + if (res->flags & IORESOURCE_IO) {
> > > > + unsigned long port = -1;
> > > > + int err = pci_register_io_range(range->cpu_addr, range->size);
> > > > + if (err)
> > > > + goto invalid_range;
> > > > + port = pci_address_to_pio(range->cpu_addr);
> > > > + if (port == (unsigned long)-1) {
> > > > + err = -EINVAL;
> > > > + goto invalid_range;
> > > > + }
> > > > + res->start = port;
> > > > + } else {
> > >
> > > This one concatenates the I/O spaces and assumes that each space starts
> > > at bus address zero, and takes little precaution to avoid filling up IO_SPACE_LIMIT
> > > if the sizes are too big.
> >
> > Actually, you are attaching too much meaning to this one. pci_register_io_range()
> > only tries to remember the ranges, nothing else. And it *does* check that the
> > total sum of registered ranges does not exceed IO_SPACE_LIMIT. This is used before
> > we have any resource mapped for that range (actually it is used to *create* the
> > resource for the range) so there is no other helping hand.
> >
> > It doesn't assume that space starts at bus address zero, it ignores the bus address.
> > It only handles CPU addresses for the range, to help with generating logical IO ports.
> > If you have overlapping CPU addresses with different bus addresses it will not work,
> > but then I guess you will have different problems then.
>
> The problem is that it tries to set up a mapping so that pci_address_to_pio
> returns the actual port number, but the port that you assign to res->start
> above is assumed to match the 'start' variable below. If the value ends
> up different, the BARs that get set by the PCI bus scan are not in the
> same place that got ioremapped into the virtual I/O aperture.
Yes, after writting a reply trying to justify why it would actually work I've realised
where the fault of my logic stands (short version, two host controllers will get different
io_offsets but the ports numbers will start from zero leading to confusion about which
host controller the resource belongs to).
I will try to split your function into two parts, one that calculates the io_offset and
another that does the ioremap_page_range() side and replace my cooked function.
Best regards,
Liviu
>
> > > >+unsigned long pci_ioremap_io(const struct resource *res, phys_addr_t phys_addr)
> > > >+{
> > > >+ unsigned long start, len, virt_start;
> > > >+ int err;
> > > >+
> > > >+ if (res->end > IO_SPACE_LIMIT)
> > > >+ return -EINVAL;
> > > >+
> > > >+ /*
> > > >+ * try finding free space for the whole size first,
> > > >+ * fall back to 64K if not available
> > > >+ */
> > > >+ len = resource_size(res);
> > > >+ start = bitmap_find_next_zero_area(pci_iospace, IO_SPACE_PAGES,
> > > >+ res->start / PAGE_SIZE, len / PAGE_SIZE, 0);
> > > >+ if (start == IO_SPACE_PAGES && len > SZ_64K) {
> > > >+ len = SZ_64K;
> > > >+ start = 0;
> > > >+ start = bitmap_find_next_zero_area(pci_iospace, IO_SPACE_PAGES,
> > > >+ start, len / PAGE_SIZE, 0);
> > > >+ }
> > > >+
> > > >+ /* no 64K area found */
> > > >+ if (start == IO_SPACE_PAGES)
> > > >+ return -ENOMEM;
> > > >+
> > > >+ /* ioremap physical aperture to virtual aperture */
> > > >+ virt_start = start * PAGE_SIZE + (unsigned long)PCI_IOBASE;
> > > >+ err = ioremap_page_range(virt_start, virt_start + len,
> > > >+ phys_addr, __pgprot(PROT_DEVICE_nGnRE));
> > > >+ if (err)
> > > >+ return err;
> > > >+
> > > >+ bitmap_set(pci_iospace, start, len / PAGE_SIZE);
> > > >+
> > > >+ /* return io_offset */
> > > >+ return start * PAGE_SIZE - res->start;
> > > >+}
>
> Arnd
>
--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
¯\_(ツ)_/¯
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