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SubjectRE: Purpose of pci_remap_iospace
Date
 > On Wednesday, July 13, 2016 8:11:56 AM CEST Bharat Kumar Gogada wrote:
> > > Subject: Re: Purpose of pci_remap_iospace
> > >
> > > On Tuesday, July 12, 2016 6:57:10 AM CEST Bharat Kumar Gogada wrote:
> > > > Hi,
> > > >
> > > > I have a query.
> > > >
> > > > Can any once explain the purpose of pci_remap_iospace function in
> root
> > > port driver.
> > > >
> > > > What is its dependency with architecture ?
> > > >
> > > > Here is my understanding, the above API takes PCIe IO resource and its
> > > > to be mapped CPU address from ranges property and remaps into
> virtual
> > > address space.
> > > >
> > > > So my question is who uses this virtual addresses ?
> > >
> > > The inb()/outb() functions declared in asm/io.h
> > >
> > > > When End Point requests for IO BARs doesn't it get from the above
> > > > resource range (first parameter of API) and do ioremap to access this
> > > > region ?
> > >
> > > Device drivers generally do not ioremap() the I/O BARs but they use
> > > inb()/outb() directly. They can also call pci_iomap() and do
> > > ioread8()/iowrite8() on the pointer returned from that function, but
> > > generally the call to pci_iomap() then returns a pointer into the virtual
> > > address that is already mapped.
> > >
> > > > But why root complex driver is mapping this address region ?
> > >
> > > The PCI core does not know that the I/O space is memory mapped.
> > > On x86 and a few others, I/O space is not memory mapped but requires
> the
> > > use of special CPU instructions.
> > >
> > Thanks Arnd.
> >
> > I'm facing issue in testing IO bars on our SoC.
> >
> > I added following ranges in our device tree :
> > ranges = <0x01000000 0x00000000 0x00000000 0x00000000 0xe0000000 0
> 0x00100000 //io
> > 0x02000000 0x00000000 0xe0100000 0x00000000 0xe0100000 0
> 0x0ef00000>; //non prefetchabe memory
> >
> > And I'm using above API to map the res and cpu physical address in my
> driver.
>
> I notice you have 1MB of I/O space here
>
> > Kernel Boot log:
> > [ 2.345294] nwl-pcie fd0e0000.pcie: Link is UP
> > [ 2.345339] PCI host bridge /amba/pcie@fd0e0000 ranges:
> > [ 2.345356] No bus range found for /amba/pcie@fd0e0000, using [bus
> 00-ff]
> > [ 2.345382] IO 0xe0000000..0xe00fffff -> 0x00000000
> > [ 2.345401] MEM 0xe0100000..0xeeffffff -> 0xe0100000
> > [ 2.345498] nwl-pcie fd0e0000.pcie: PCI host bridge to bus 0000:00
> > [ 2.345517] pci_bus 0000:00: root bus resource [bus 00-ff]
> > [ 2.345533] pci_bus 0000:00: root bus resource [io 0x0000-0xfffff]
>
> and all of it gets mapped by the PCI core. Usually you only have 64K of I/O
> space per host bridge, and the PCI core should perhaps not try to map
> all of it, though I don't think this is actually your problem here.
>
> > [ 2.345550] pci_bus 0000:00: root bus resource [mem 0xe0100000-
> 0xeeffffff]
> > [ 2.345770] pci 0000:00:00.0: cannot attach to SMMU, is it on the same
> bus?
> > [ 2.345786] iommu: Adding device 0000:00:00.0 to group 1
> > [ 2.346142] pci 0000:01:00.0: cannot attach to SMMU, is it on the same
> bus?
> > [ 2.346158] iommu: Adding device 0000:01:00.0 to group 1
> > [ 2.346213] pci 0000:00:00.0: BAR 8: assigned [mem 0xe0100000-
> 0xe02fffff]
> > [ 2.346234] pci 0000:01:00.0: BAR 0: assigned [mem 0xe0100000-0xe01fffff
> 64bit]
> > [ 2.346268] pci 0000:01:00.0: BAR 2: assigned [mem 0xe0200000-0xe02fffff
> 64bit]
> > [ 2.346300] pci 0000:01:00.0: BAR 4: no space for [io size 0x0040]
> > [ 2.346316] pci 0000:01:00.0: BAR 4: failed to assign [io size 0x0040]
> > [ 2.346333] pci 0000:00:00.0: PCI bridge to [bus 01-0c]
> > [ 2.346350] pci 0000:00:00.0: bridge window [mem 0xe0100000-
> 0xe02fffff]
> >
> > IO assignment fails.
>
> I would guess that the I/O space is not registered correctly. Is this
> drivers/pci/host/pcie-xilinx.c ? We have had problems with this in the
> past, since almost nobody uses I/O space and it requires several
> steps to all be done correctly.
>
Thanks Arnd.

we are testing using drivers/pci/host/pcie-xilinx-nwl.c.

Here is the code I added to driver in probe:
..
err = of_pci_get_host_bridge_resources(node, 0, 0xff, &res, &iobase);
if (err) {
pr_err("Getting bridge resources failed\n");
return err;
}
resource_list_for_each_entry(window, &res) { //code for io resource
struct resource *res = window->res;
u64 restype = resource_type(res);

switch (restype) {
case IORESOURCE_IO:
err = pci_remap_iospace(res, iobase);
if(err)
pr_info("FAILED TO IPREMAP RESOURCE\n");
break;
default:
dev_err(pcie->dev, "invalid resource %pR\n", res);

}
}

Other than above code I haven't done any change in driver.

Here is the printk added boot log:
[ 2.308680] nwl-pcie fd0e0000.pcie: Link is UP
[ 2.308724] PCI host bridge /amba/pcie@fd0e0000 ranges:
[ 2.308741] No bus range found for /amba/pcie@fd0e0000, using [bus 00-ff]
[ 2.308755] in pci_add_resource_offset res->start 0 offset 0
[ 2.308774] IO 0xe0000000..0xe00fffff -> 0x00000000
[ 2.308795] in pci_add_resource_offset res->start 0 offset 0
[ 2.308805] MEM 0xe0100000..0xeeffffff -> 0xe0100000
[ 2.308824] in pci_add_resource_offset res->start e0100000 offset 0
[ 2.308834] nwl-pcie fd0e0000.pcie: invalid resource [bus 00-ff]
[ 2.308870] nwl-pcie fd0e0000.pcie: invalid resource [mem 0xe0100000-0xeeffffff]
[ 2.308979] nwl-pcie fd0e0000.pcie: PCI host bridge to bus 0000:00
[ 2.308998] pci_bus 0000:00: root bus resource [bus 00-ff]
[ 2.309014] pci_bus 0000:00: root bus resource [io 0x0000-0xfffff]
[ 2.309030] pci_bus 0000:00: root bus resource [mem 0xe0100000-0xeeffffff]
[ 2.309253] pci 0000:00:00.0: cannot attach to SMMU, is it on the same bus?
[ 2.309269] iommu: Adding device 0000:00:00.0 to group 1
[ 2.309625] pci 0000:01:00.0: cannot attach to SMMU, is it on the same bus?
[ 2.309641] iommu: Adding device 0000:01:00.0 to group 1
[ 2.309697] pci 0000:00:00.0: BAR 8: assigned [mem 0xe0100000-0xe02fffff]
[ 2.309718] pci 0000:01:00.0: BAR 0: assigned [mem 0xe0100000-0xe01fffff 64bit]
[ 2.309752] pci 0000:01:00.0: BAR 2: assigned [mem 0xe0200000-0xe02fffff 64bit]
[ 2.309784] pci 0000:01:00.0: BAR 4: no space for [io size 0x0040]
[ 2.309800] pci 0000:01:00.0: BAR 4: failed to assign [io size 0x0040]
[ 2.309816] pci 0000:00:00.0: PCI bridge to [bus 01-0c]
[ 2.309833] pci 0000:00:00.0: bridge window [mem 0xe0100000-0xe02fffff]

Here is the output of ioports and iomem:

root@:~# cat /proc/iomem
00000000-7fffffff : System RAM
00080000-00a76fff : Kernel code
01c72000-01d4bfff : Kernel data
fd0c0000-fd0c1fff : /amba/ahci@fd0c0000
fd0e0000-fd0e0fff : breg
fd480000-fd480fff : pcireg
ff000000-ff000fff : xuartps
ff010000-ff010fff : xuartps
ff020000-ff020fff : /amba/i2c@ff020000
ff030000-ff030fff : /amba/i2c@ff030000
ff070000-ff070fff : /amba/can@ff070000
ff0a0000-ff0a0fff : /amba/gpio@ff0a0000
ff0f0000-ff0f0fff : /amba/spi@ff0f0000
ff170000-ff170fff : mmc0
ffa60000-ffa600ff : /amba/rtc@ffa60000
8000000000-8000ffffff : cfg
root@:~# cat /proc/ioports
root@:~#

/proc/ioports is empty.

Thanks & Regards,
Bharat


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