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SubjectRe: [Patch 1/1] x86 pci: Add option to not assign BAR's if not already assigned
Any further consideration for this patch, or has it been rejected?

Thanks, Mike

Mike Travis wrote:
> Subject: [Patch 1/1] x86 pci: Add option to not assign BAR's if not
> already assigned
> From: Mike Habeck <habeck@sgi.com>
>
> The Linux kernel assigns BARs that a BIOS did not assign, most likely
> to handle broken BIOSes that didn't enumerate the devices correctly.
> On UV the BIOS purposely doesn't assign I/O BARs for certain devices/
> drivers we know don't use them (examples, LSI SAS, Qlogic FC, ...).
> We purposely don't assign these I/O BARs because I/O Space is a very
> limited resource. There is only 64k of I/O Space, and in a PCIe
> topology that space gets divided up into 4k chucks (this is due to
> the fact that a pci-to-pci bridge's I/O decoder is aligned at 4k)...
> Thus a system can have at most 16 cards with I/O BARs: (64k / 4k = 16)
>
> SGI needs to scale to >16 devices with I/O BARs. So by not assigning
> I/O BARs on devices we know don't use them, we can do that (iff the
> kernel doesn't go and assign these BARs that the BIOS purposely didn't
> assign).
>
> This patch will not assign a resource to a device BAR if that BAR was
> not assigned by the BIOS, and the kernel cmdline option 'pci=nobar'
> was specified. This patch is closely modeled after the 'pci=norom'
> option that currently exists in the tree.
>
> Signed-off-by: Mike Habeck <habeck@sgi.com>
> Signed-off-by: Mike Travis <travis@sgi.com>
> ---
> Documentation/kernel-parameters.txt | 2 ++
> arch/x86/include/asm/pci_x86.h | 1 +
> arch/x86/pci/common.c | 20 ++++++++++++++++++++
> 3 files changed, 23 insertions(+)
>
> --- linux.orig/Documentation/kernel-parameters.txt
> +++ linux/Documentation/kernel-parameters.txt
> @@ -1935,6 +1935,8 @@ and is between 256 and 4096 characters.
> norom [X86] Do not assign address space to
> expansion ROMs that do not already have
> BIOS assigned address ranges.
> + nobar [X86] Do not assign address space to the
> + BARs that weren't assigned by the BIOS.
> irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
> assigned automatically to PCI devices. You can
> make the kernel exclude IRQs of your ISA cards
> --- linux.orig/arch/x86/include/asm/pci_x86.h
> +++ linux/arch/x86/include/asm/pci_x86.h
> @@ -30,6 +30,7 @@
> #define PCI_HAS_IO_ECS 0x40000
> #define PCI_NOASSIGN_ROMS 0x80000
> #define PCI_ROOT_NO_CRS 0x100000
> +#define PCI_NOASSIGN_BARS 0x200000
>
> extern unsigned int pci_probe;
> extern unsigned long pirq_table_addr;
> --- linux.orig/arch/x86/pci/common.c
> +++ linux/arch/x86/pci/common.c
> @@ -125,6 +125,23 @@ void __init dmi_check_skip_isa_align(voi
> static void __devinit pcibios_fixup_device_resources(struct pci_dev *dev)
> {
> struct resource *rom_r = &dev->resource[PCI_ROM_RESOURCE];
> + struct resource *bar_r;
> + int bar;
> +
> + if (pci_probe & PCI_NOASSIGN_BARS) {
> + /*
> + * If the BIOS did not assign the BAR, zero out the
> + * resource so the kernel doesn't attmept to assign
> + * it later on in pci_assign_unassigned_resources
> + */
> + for (bar = 0; bar <= PCI_STD_RESOURCE_END; bar++) {
> + bar_r = &dev->resource[bar];
> + if (bar_r->start == 0 && bar_r->end != 0) {
> + bar_r->flags = 0;
> + bar_r->end = 0;
> + }
> + }
> + }
>
> if (pci_probe & PCI_NOASSIGN_ROMS) {
> if (rom_r->parent)
> @@ -509,6 +526,9 @@ char * __devinit pcibios_setup(char *st
> } else if (!strcmp(str, "norom")) {
> pci_probe |= PCI_NOASSIGN_ROMS;
> return NULL;
> + } else if (!strcmp(str, "nobar")) {
> + pci_probe |= PCI_NOASSIGN_BARS;
> + return NULL;
> } else if (!strcmp(str, "assign-busses")) {
> pci_probe |= PCI_ASSIGN_ALL_BUSSES;
> return NULL;


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