Re: [PATCH 03/13] sparc/PCI: Reserve legacy mmio after PCI mmio

From: Bjorn Helgaas
Date: Wed May 03 2017 - 18:04:16 EST

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On Thu, Apr 20, 2017 at 10:04:50PM -0700, Yinghai Lu wrote:
> On one system found bunch of claim resource fail from pci device.
> pci_sun4v f02b894c: PCI host bridge to bus 0000:00
> pci_bus 0000:00: root bus resource [io 0x2007e00000000-0x2007e0fffffff] (bus address [0x0000-0xfffffff])
> pci_bus 0000:00: root bus resource [mem 0x2000000000000-0x200007effffff] (bus address [0x00000000-0x7effffff])
> pci_bus 0000:00: root bus resource [mem 0x2000100000000-0x20007ffffffff] (bus address [0x100000000-0x7ffffffff])
> ...
> PCI: Claiming 0000:00:02.0: Resource 14: 0002000000000000..00020000004fffff [200]
> pci 0000:00:02.0: can't claim BAR 14 [mem 0x2000000000000-0x20000004fffff]: address conflict with Video RAM area [??? 0x20000000a0000-0x20000000bffff flags 0x80000000]
> pci 0000:02:00.0: can't claim BAR 0 [mem 0x2000000000000-0x20000000fffff]: no compatible bridge window
> PCI: Claiming 0000:02:00.0: Resource 3: 0002000000100000..0002000000103fff [200]
> pci 0000:02:00.0: can't claim BAR 3 [mem 0x2000000100000-0x2000000103fff]: no compatible bridge window
> PCI: Claiming 0000:02:00.1: Resource 0: 0002000000200000..00020000002fffff [200]
> pci 0000:02:00.1: can't claim BAR 0 [mem 0x2000000200000-0x20000002fffff]: no compatible bridge window
> PCI: Claiming 0000:02:00.1: Resource 3: 0002000000104000..0002000000107fff [200]
> pci 0000:02:00.1: can't claim BAR 3 [mem 0x2000000104000-0x2000000107fff]: no compatible bridge window
> PCI: Claiming 0000:02:00.2: Resource 0: 0002000000300000..00020000003fffff [200]
> pci 0000:02:00.2: can't claim BAR 0 [mem 0x2000000300000-0x20000003fffff]: no compatible bridge window
> PCI: Claiming 0000:02:00.2: Resource 3: 0002000000108000..000200000010bfff [200]
> pci 0000:02:00.2: can't claim BAR 3 [mem 0x2000000108000-0x200000010bfff]: no compatible bridge window
> PCI: Claiming 0000:02:00.3: Resource 0: 0002000000400000..00020000004fffff [200]
> pci 0000:02:00.3: can't claim BAR 0 [mem 0x2000000400000-0x20000004fffff]: no compatible bridge window
> PCI: Claiming 0000:02:00.3: Resource 3: 000200000010c000..000200000010ffff [200]
> pci 0000:02:00.3: can't claim BAR 3 [mem 0x200000010c000-0x200000010ffff]: no compatible bridge window
>
> The bridge 00:02.0 resource does not get reserved as Video RAM take the position early,
> and following children resources reservation all fail.
>
> Move down Video RAM area reservation after pci mmio get reserved,
> so we leave pci driver to use those regions.

I think this patch contains two changes:

1) Factor pci_register_region() out of pci_register_legacy_regions()
and do the correct bus-to-resource conversion, and

2) Call pci_register_legacy_regions() from pci_scan_one_pbm() after
scanning the bus instead of from pci_determine_mem_io_space()
before.

Can you split this into two patches, one for each change?

pci_register_legacy_regions() reserves these bus address regions:

[0xa0000-0xbffff] Video RAM
[0xc0000-0xc7fff] Video ROM
[0xf0000-0xfffff] System ROM

>From a PCI point of view, address space usage is normally reported by
BARs, and we register legacy regions to account for address space
that's not reported by a BAR.

For a legacy VGA device, I think that's only [0xa0000-0xbffff] (plus
some I/O ports). I don't think a PCI device should ever use the ROM
regions mentioned above unless it has a BAR programmed to those
addresses, so I'm not sure we need to reserve them as PCI "legacy"
regions.

I suspect those ROM areas might have been copied from x86 BIOS stuff
and might not be applicable on sparc. If you want to reserve them to
preserve the previous behavior, that's OK, but maybe we could do it
with a separate "sparc_register_legacy_regions()" or something?

I'm thinking that the VGA part of this is not really arch-specific, so
we could someday factor that out into the PCI core so you wouldn't
have to do that part in the sparc code, and splitting out the non-PCI
stuff would make that easier.

I guess we reserve the VGA RAM either for a VGA device already in the
system or to reserve space for one that might be hotplugged later. In
your example above, there's a non-VGA device using that area, so I
suppose this patch means the 02:00.0 BAR 0 reservation works
correctly, but the subsequent VGA reservation complains about a
conflict with 02:00.0? That "address conflict" message isn't really
accurate: there's no actual conflict because there's no VGA device.
The failure just means we won't be able to hot-add a VGA device later,
right?

> -v5: merge simplify one and use pcibios_bus_to_resource()
>
> -v6: use pci_find_bus_resource()
>
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> Tested-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
> Cc: sparclinux@xxxxxxxxxxxxxxx
> ---
> arch/sparc/kernel/pci.c | 1 +
> arch/sparc/kernel/pci_common.c | 59 ++++++++++++++++++++++--------------------
> arch/sparc/kernel/pci_impl.h | 1 +
> 3 files changed, 33 insertions(+), 28 deletions(-)
>
> diff --git a/arch/sparc/kernel/pci.c b/arch/sparc/kernel/pci.c
> index c5cf813..adb9653 100644
> --- a/arch/sparc/kernel/pci.c
> +++ b/arch/sparc/kernel/pci.c
> @@ -686,6 +686,7 @@ struct pci_bus *pci_scan_one_pbm(struct pci_pbm_info *pbm,
> pci_bus_register_of_sysfs(bus);
>
> pci_claim_bus_resources(bus);
> + pci_register_legacy_regions(bus);
> pci_bus_add_devices(bus);
> return bus;
> }
> diff --git a/arch/sparc/kernel/pci_common.c b/arch/sparc/kernel/pci_common.c
> index 76998f8..1ebc7ff 100644
> --- a/arch/sparc/kernel/pci_common.c
> +++ b/arch/sparc/kernel/pci_common.c
> @@ -328,41 +328,46 @@ void pci_get_pbm_props(struct pci_pbm_info *pbm)
> }
> }
>
> -static void pci_register_legacy_regions(struct resource *io_res,
> - struct resource *mem_res)
> +static void pci_register_region(struct pci_bus *bus, const char *name,
> + resource_size_t rstart, resource_size_t size)
> {
> - struct resource *p;
> + struct resource *res, *conflict, *bus_res;
> + struct pci_bus_region region;
>
> - /* VGA Video RAM. */
> - p = kzalloc(sizeof(*p), GFP_KERNEL);
> - if (!p)
> + res = kzalloc(sizeof(*res), GFP_KERNEL);
> + if (!res)
> return;
>
> - p->name = "Video RAM area";
> - p->start = mem_res->start + 0xa0000UL;
> - p->end = p->start + 0x1ffffUL;
> - p->flags = IORESOURCE_BUSY;
> - request_resource(mem_res, p);
> + res->flags = IORESOURCE_MEM;
>
> - p = kzalloc(sizeof(*p), GFP_KERNEL);
> - if (!p)
> + region.start = rstart;
> + region.end = rstart + size - 1UL;
> + pcibios_bus_to_resource(bus, res, &region);
> + bus_res = pci_find_bus_resource(bus, res);
> + if (!bus_res) {
> + kfree(res);
> return;
> + }
> +
> + res->name = name;
> + res->flags |= IORESOURCE_BUSY;
> + conflict = request_resource_conflict(bus_res, res);
> + if (conflict) {
> + dev_printk(KERN_DEBUG, &bus->dev,
> + " can't claim %s %pR: address conflict with %s %pR\n",
> + res->name, res, conflict->name, conflict);
> + kfree(res);
> + }
> +}
>
> - p->name = "System ROM";
> - p->start = mem_res->start + 0xf0000UL;
> - p->end = p->start + 0xffffUL;
> - p->flags = IORESOURCE_BUSY;
> - request_resource(mem_res, p);
> +void pci_register_legacy_regions(struct pci_bus *bus)
> +{
> + /* VGA Video RAM. */
> + pci_register_region(bus, "Video RAM area", 0xa0000UL, 0x20000UL);
>
> - p = kzalloc(sizeof(*p), GFP_KERNEL);
> - if (!p)
> - return;
> + pci_register_region(bus, "System ROM", 0xf0000UL, 0x10000UL);
>
> - p->name = "Video ROM";
> - p->start = mem_res->start + 0xc0000UL;
> - p->end = p->start + 0x7fffUL;
> - p->flags = IORESOURCE_BUSY;
> - request_resource(mem_res, p);
> + pci_register_region(bus, "Video ROM", 0xc0000UL, 0x8000UL);
> }
>
> static void pci_register_iommu_region(struct pci_pbm_info *pbm)
> @@ -504,8 +509,6 @@ void pci_determine_mem_io_space(struct pci_pbm_info *pbm)
> if (pbm->mem64_space.flags)
> request_resource(&iomem_resource, &pbm->mem64_space);
>
> - pci_register_legacy_regions(&pbm->io_space,
> - &pbm->mem_space);
> pci_register_iommu_region(pbm);
> }
>
> diff --git a/arch/sparc/kernel/pci_impl.h b/arch/sparc/kernel/pci_impl.h
> index 2853af7..ff8f5e1 100644
> --- a/arch/sparc/kernel/pci_impl.h
> +++ b/arch/sparc/kernel/pci_impl.h
> @@ -167,6 +167,7 @@ void pci_get_pbm_props(struct pci_pbm_info *pbm);
> struct pci_bus *pci_scan_one_pbm(struct pci_pbm_info *pbm,
> struct device *parent);
> void pci_determine_mem_io_space(struct pci_pbm_info *pbm);
> +void pci_register_legacy_regions(struct pci_bus *bus);
>
> /* Error reporting support. */
> void pci_scan_for_target_abort(struct pci_pbm_info *, struct pci_bus *);
> --
> 2.9.3
>

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