Re: [PATCH] PCI: Try to find two continuous regions for child resource

From: Bjorn Helgaas
Date: Mon Mar 29 2021 - 12:23:27 EST

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On Mon, Mar 29, 2021 at 04:47:59PM +0800, Kai-Heng Feng wrote:
> Built-in grahpics on HP EliteDesk 805 G6 doesn't work because graphics
> can't get the BAR it needs:
> [ 0.611504] pci_bus 0000:00: root bus resource [mem 0x10020200000-0x100303fffff window]
> [ 0.611505] pci_bus 0000:00: root bus resource [mem 0x10030400000-0x100401fffff window]
> ...
> [ 0.638083] pci 0000:00:08.1: bridge window [mem 0xd2000000-0xd23fffff]
> [ 0.638086] pci 0000:00:08.1: bridge window [mem 0x10030000000-0x100401fffff 64bit pref]
> [ 0.962086] pci 0000:00:08.1: can't claim BAR 15 [mem 0x10030000000-0x100401fffff 64bit pref]: no compatible bridge window
> [ 0.962086] pci 0000:00:08.1: [mem 0x10030000000-0x100401fffff 64bit pref] clipped to [mem 0x10030000000-0x100303fffff 64bit pref]
> [ 0.962086] pci 0000:00:08.1: bridge window [mem 0x10030000000-0x100303fffff 64bit pref]
> [ 0.962086] pci 0000:07:00.0: can't claim BAR 0 [mem 0x10030000000-0x1003fffffff 64bit pref]: no compatible bridge window
> [ 0.962086] pci 0000:07:00.0: can't claim BAR 2 [mem 0x10040000000-0x100401fffff 64bit pref]: no compatible bridge window
>
> However, the root bus has two continuous regions that can contain the
> child resource requested.
>
> So try to find another parent region if two regions are continuous and
> can contain child resource. This change makes the grahpics works on the
> system in question.

The BIOS description of PCI0 is interesting:

pci_bus 0000:00: root bus resource [mem 0x10000000000-0x100201fffff window]
pci_bus 0000:00: root bus resource [mem 0x10020200000-0x100303fffff window]
pci_bus 0000:00: root bus resource [mem 0x10030400000-0x100401fffff window]

So the PCI0 _CRS apparently gave us:

[mem 0x10000000000-0x100201fffff] size 0x20200000 (512MB + 2MB)
[mem 0x10020200000-0x100303fffff] size 0x10200000 (256MB + 2MB)
[mem 0x10030400000-0x100401fffff] size 0x0fe00000 (254MB)

These are all contiguous, so we'd have no problem if we coalesced them
into a single window:

[mem 0x10000000000-0x100401fffff window] size 0x40200000 (1GB + 2MB)

I think we currently keep these root bus resources separate because if
we ever support _SRS for host bridges, the argument we give to _SRS
must be exactly the same format as what we got from _CRS (see ACPI
v6.3, sec 6.2.16, and pnpacpi_set_resources()).

pnpacpi_encode_resources() is currently very simple-minded and copies
each device resource back into a single _SRS entry. But (1) we don't
support _SRS for host bridges, and (2) if we ever do, we can make
pnpacpi_encode_resources() smarter so it breaks things back up.

So I think we should try to fix this by coalescing these adjacent
resources from _CRS so we end up with a single root bus resource that
covers all contiguous regions.

Typos, etc:
- No need for the timestamps; they're not relevant to the problem.
- s/grahpics/graphics/ (two occurrences above)
- s/continuous/contiguous/ (three occurrences above)

> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212013
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> ---
> arch/microblaze/pci/pci-common.c | 4 +--
> arch/powerpc/kernel/pci-common.c | 8 ++---
> arch/sparc/kernel/pci.c | 4 +--
> drivers/pci/pci.c | 60 +++++++++++++++++++++++++++-----
> drivers/pci/setup-res.c | 21 +++++++----
> drivers/pcmcia/rsrc_nonstatic.c | 4 +--
> include/linux/pci.h | 6 ++--
> 7 files changed, 80 insertions(+), 27 deletions(-)
>
> diff --git a/arch/microblaze/pci/pci-common.c b/arch/microblaze/pci/pci-common.c
> index 557585f1be41..8e65832fb510 100644
> --- a/arch/microblaze/pci/pci-common.c
> +++ b/arch/microblaze/pci/pci-common.c
> @@ -669,7 +669,7 @@ static void pcibios_allocate_bus_resources(struct pci_bus *bus)
> {
> struct pci_bus *b;
> int i;
> - struct resource *res, *pr;
> + struct resource *res, *pr = NULL;
>
> pr_debug("PCI: Allocating bus resources for %04x:%02x...\n",
> pci_domain_nr(bus), bus->number);
> @@ -688,7 +688,7 @@ static void pcibios_allocate_bus_resources(struct pci_bus *bus)
> * and as such ensure proper re-allocation
> * later.
> */
> - pr = pci_find_parent_resource(bus->self, res);
> + pci_find_parent_resource(bus->self, res, &pr, NULL);
> if (pr == res) {
> /* this happens when the generic PCI
> * code (wrongly) decides that this
> diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
> index 001e90cd8948..f865354b746d 100644
> --- a/arch/powerpc/kernel/pci-common.c
> +++ b/arch/powerpc/kernel/pci-common.c
> @@ -1196,7 +1196,7 @@ static void pcibios_allocate_bus_resources(struct pci_bus *bus)
> {
> struct pci_bus *b;
> int i;
> - struct resource *res, *pr;
> + struct resource *res, *pr = NULL;
>
> pr_debug("PCI: Allocating bus resources for %04x:%02x...\n",
> pci_domain_nr(bus), bus->number);
> @@ -1213,7 +1213,7 @@ static void pcibios_allocate_bus_resources(struct pci_bus *bus)
> pr = (res->flags & IORESOURCE_IO) ?
> &ioport_resource : &iomem_resource;
> else {
> - pr = pci_find_parent_resource(bus->self, res);
> + pci_find_parent_resource(bus->self, res, &pr, NULL);
> if (pr == res) {
> /* this happens when the generic PCI
> * code (wrongly) decides that this
> @@ -1265,12 +1265,12 @@ static void pcibios_allocate_bus_resources(struct pci_bus *bus)
>
> static inline void alloc_resource(struct pci_dev *dev, int idx)
> {
> - struct resource *pr, *r = &dev->resource[idx];
> + struct resource *pr = NULL, *r = &dev->resource[idx];
>
> pr_debug("PCI: Allocating %s: Resource %d: %pR\n",
> pci_name(dev), idx, r);
>
> - pr = pci_find_parent_resource(dev, r);
> + pci_find_parent_resource(dev, r, &pr, NULL);
> if (!pr || (pr->flags & IORESOURCE_UNSET) ||
> request_resource(pr, r) < 0) {
> printk(KERN_WARNING "PCI: Cannot allocate resource region %d"
> diff --git a/arch/sparc/kernel/pci.c b/arch/sparc/kernel/pci.c
> index 9c2b720bfd20..b4006798e4e1 100644
> --- a/arch/sparc/kernel/pci.c
> +++ b/arch/sparc/kernel/pci.c
> @@ -621,7 +621,7 @@ static void pci_bus_register_of_sysfs(struct pci_bus *bus)
> static void pci_claim_legacy_resources(struct pci_dev *dev)
> {
> struct pci_bus_region region;
> - struct resource *p, *root, *conflict;
> + struct resource *p, *root = NULL, *conflict;
>
> if ((dev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
> return;
> @@ -637,7 +637,7 @@ static void pci_claim_legacy_resources(struct pci_dev *dev)
> region.end = region.start + 0x1ffffUL;
> pcibios_bus_to_resource(dev->bus, p, &region);
>
> - root = pci_find_parent_resource(dev, p);
> + pci_find_parent_resource(dev, p, &root, NULL);
> if (!root) {
> pci_info(dev, "can't claim VGA legacy %pR: no compatible bridge window\n", p);
> goto err;
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 16a17215f633..abbcd2dcdc02 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -693,20 +693,25 @@ u8 pci_find_ht_capability(struct pci_dev *dev, int ht_cap)
> EXPORT_SYMBOL_GPL(pci_find_ht_capability);
>
> /**
> - * pci_find_parent_resource - return resource region of parent bus of given
> + * pci_find_parent_resource - find resource region of parent bus of given
> * region
> * @dev: PCI device structure contains resources to be searched
> * @res: child resource record for which parent is sought
> + * @first: the first region that contains the child resource
> + * @second: the second region that combines with the first region to fully
> + * contains the child resource
> *
> * For given resource region of given device, return the resource region of
> * parent bus the given region is contained in.
> */
> -struct resource *pci_find_parent_resource(const struct pci_dev *dev,
> - struct resource *res)
> +void pci_find_parent_resource(const struct pci_dev *dev,
> + struct resource *res,
> + struct resource **first,
> + struct resource **second)
> {
> const struct pci_bus *bus = dev->bus;
> struct resource *r;
> - int i;
> + int i, overlaps = 0;
>
> pci_bus_for_each_resource(bus, r, i) {
> if (!r)
> @@ -718,8 +723,10 @@ struct resource *pci_find_parent_resource(const struct pci_dev *dev,
> * not, the allocator made a mistake.
> */
> if (r->flags & IORESOURCE_PREFETCH &&
> - !(res->flags & IORESOURCE_PREFETCH))
> - return NULL;
> + !(res->flags & IORESOURCE_PREFETCH)) {
> + *first = NULL;
> + return;
> + }
>
> /*
> * If we're below a transparent bridge, there may
> @@ -729,10 +736,47 @@ struct resource *pci_find_parent_resource(const struct pci_dev *dev,
> * on pci_bus_for_each_resource() giving us those
> * first.
> */
> - return r;
> + *first = r;
> + return;
> }
> }
> - return NULL;
> +
> + if (!second)
> + return;
> +
> + pci_bus_for_each_resource(bus, r, i) {
> + if (!r)
> + continue;
> + if (resource_overlaps(r, res)) {
> + if (r->flags & IORESOURCE_PREFETCH &&
> + !(res->flags & IORESOURCE_PREFETCH))
> + continue;
> +
> + if (!overlaps++)
> + *first = r;
> + else {
> + *second = r;
> + break;
> + }
> + }
> + }
> +
> + if (overlaps != 2)
> + goto out;
> +
> + if ((*first)->start > (*second)->start)
> + swap(*first, *second);
> +
> + if ((*first)->end + 1 != (*second)->start)
> + goto out;
> +
> + if ((*first)->start <= res->start && (*second)->end >= res->end)
> + return;
> +out:
> +
> + *first = NULL;
> + *second = NULL;
> + return;
> }
> EXPORT_SYMBOL(pci_find_parent_resource);
>
> diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
> index 7f1acb3918d0..e39615321d81 100644
> --- a/drivers/pci/setup-res.c
> +++ b/drivers/pci/setup-res.c
> @@ -131,7 +131,7 @@ void pci_update_resource(struct pci_dev *dev, int resno)
> int pci_claim_resource(struct pci_dev *dev, int resource)
> {
> struct resource *res = &dev->resource[resource];
> - struct resource *root, *conflict;
> + struct resource *first = NULL, *second = NULL, *conflict;
>
> if (res->flags & IORESOURCE_UNSET) {
> pci_info(dev, "can't claim BAR %d %pR: no address assigned\n",
> @@ -147,21 +147,28 @@ int pci_claim_resource(struct pci_dev *dev, int resource)
> if (res->flags & IORESOURCE_ROM_SHADOW)
> return 0;
>
> - root = pci_find_parent_resource(dev, res);
> - if (!root) {
> + pci_find_parent_resource(dev, res, &first, &second);
> + if (!first) {
> pci_info(dev, "can't claim BAR %d %pR: no compatible bridge window\n",
> resource, res);
> res->flags |= IORESOURCE_UNSET;
> return -EINVAL;
> }
>
> - conflict = request_resource_conflict(root, res);
> + if (second)
> + first->end = second->end;
> +
> + conflict = request_resource_conflict(first, res);
> if (conflict) {
> + if (second)
> + first->end = second->start - 1;
> +
> pci_info(dev, "can't claim BAR %d %pR: address conflict with %s %pR\n",
> resource, res, conflict->name, conflict);
> res->flags |= IORESOURCE_UNSET;
> return -EBUSY;
> - }
> + } else if (second)
> + second->start = second->end = 0;
>
> return 0;
> }
> @@ -195,7 +202,7 @@ resource_size_t __weak pcibios_retrieve_fw_addr(struct pci_dev *dev, int idx)
> static int pci_revert_fw_address(struct resource *res, struct pci_dev *dev,
> int resno, resource_size_t size)
> {
> - struct resource *root, *conflict;
> + struct resource *root = NULL, *conflict;
> resource_size_t fw_addr, start, end;
>
> fw_addr = pcibios_retrieve_fw_addr(dev, resno);
> @@ -208,7 +215,7 @@ static int pci_revert_fw_address(struct resource *res, struct pci_dev *dev,
> res->end = res->start + size - 1;
> res->flags &= ~IORESOURCE_UNSET;
>
> - root = pci_find_parent_resource(dev, res);
> + pci_find_parent_resource(dev, res, &root, NULL);
> if (!root) {
> if (res->flags & IORESOURCE_IO)
> root = &ioport_resource;
> diff --git a/drivers/pcmcia/rsrc_nonstatic.c b/drivers/pcmcia/rsrc_nonstatic.c
> index 3b05760e69d6..2fba42d7486e 100644
> --- a/drivers/pcmcia/rsrc_nonstatic.c
> +++ b/drivers/pcmcia/rsrc_nonstatic.c
> @@ -73,7 +73,7 @@ static struct resource *
> claim_region(struct pcmcia_socket *s, resource_size_t base,
> resource_size_t size, int type, char *name)
> {
> - struct resource *res, *parent;
> + struct resource *res, *parent = NULL;
>
> parent = type & IORESOURCE_MEM ? &iomem_resource : &ioport_resource;
> res = pcmcia_make_resource(base, size, type | IORESOURCE_BUSY, name);
> @@ -81,7 +81,7 @@ claim_region(struct pcmcia_socket *s, resource_size_t base,
> if (res) {
> #ifdef CONFIG_PCI
> if (s && s->cb_dev)
> - parent = pci_find_parent_resource(s->cb_dev, res);
> + pci_find_parent_resource(s->cb_dev, res, &parent, NULL);
> #endif
> if (!parent || request_resource(parent, res)) {
> kfree(res);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 86c799c97b77..dd1455be5247 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1049,8 +1049,10 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus);
> unsigned int pci_scan_child_bus(struct pci_bus *bus);
> void pci_bus_add_device(struct pci_dev *dev);
> void pci_read_bridge_bases(struct pci_bus *child);
> -struct resource *pci_find_parent_resource(const struct pci_dev *dev,
> - struct resource *res);
> +void pci_find_parent_resource(const struct pci_dev *dev,
> + struct resource *res,
> + struct resource **first,
> + struct resource **second);
> u8 pci_swizzle_interrupt_pin(const struct pci_dev *dev, u8 pin);
> int pci_get_interrupt_pin(struct pci_dev *dev, struct pci_dev **bridge);
> u8 pci_common_swizzle(struct pci_dev *dev, u8 *pinp);
> --
> 2.30.2
>

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