[PATCH 1/3] ARM: bios32: use pci_enable_resource to enable PCI resources

Bjorn Helgaas
2014-02-12T01:06:50Z

On Tue, Feb 04, 2014 at 04:53:02PM +0000, Will Deacon wrote:
> This patch moves bios32 over to using the generic code for enabling PCI
> resources. All that's left to take care of is the case of PCI bridges,
> which need to be enabled for both IO and MEMORY, regardless of the
> resource types.
>
> A side-effect of this change is that we no longer explicitly enable
> devices when running in PCI_PROBE_ONLY mode. This stays closer to the
> meaning of the option and prevents us from trying to enable devices
> without any assigned resources (the core code refuses to enable
> resources without parents).

Heh, I've been looking at this, too :) I have a similar patch for ARM and
other architectures with their own versions of pcibios_enable_device().

Several of them (arm m68k tile tegra unicore32) have this special code that
enables IO and MEMORY for bridges unconditionally. But from a PCI
perspective, I don't know why we should do this unconditionally. If a
bridge doesn't have an enabled MEM window or MEM BAR, I don't think we
should have to enable PCI_COMMAND_MEMORY for it.

The architectures that do this only check for valid MEM BARs, i.e., they
only look at resources 0-5, and they don't look at the window resources.

The architectures that don't enable IO and MEMORY for bridges
unconditionally check *all* the resources up to PCI_NUM_RESOURCES, which
includes the BARs, bridge windows, and any IOV resources.

The generic pci_enable_resources() does check all the resources, so I
*think* it should be safe for all architectures to use that and just drop
the check for bridges. What do you think?

Bjorn

> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
> arch/arm/kernel/bios32.c | 35 ++++++++++-------------------------
> 1 file changed, 10 insertions(+), 25 deletions(-)
>
> diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c
> index 317da88ae65b..9f3c76638689 100644
> --- a/arch/arm/kernel/bios32.c
> +++ b/arch/arm/kernel/bios32.c
> @@ -608,40 +608,25 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res,
> */
> int pcibios_enable_device(struct pci_dev *dev, int mask)
> {
> - u16 cmd, old_cmd;
> - int idx;
> - struct resource *r;
> + int err;
> + u16 cmd;
>
> - pci_read_config_word(dev, PCI_COMMAND, &cmd);
> - old_cmd = cmd;
> - for (idx = 0; idx < 6; idx++) {
> - /* Only set up the requested stuff */
> - if (!(mask & (1 << idx)))
> - continue;
> + if (pci_has_flag(PCI_PROBE_ONLY))
> + return 0;
>
> - r = dev->resource + idx;
> - if (!r->start && r->end) {
> - printk(KERN_ERR "PCI: Device %s not available because"
> - " of resource collisions\n", pci_name(dev));
> - return -EINVAL;
> - }
> - if (r->flags & IORESOURCE_IO)
> - cmd |= PCI_COMMAND_IO;
> - if (r->flags & IORESOURCE_MEM)
> - cmd |= PCI_COMMAND_MEMORY;
> - }
> + err = pci_enable_resources(dev, mask);
> + if (err)
> + return err;
>
> /*
> * Bridges (eg, cardbus bridges) need to be fully enabled
> */
> - if ((dev->class >> 16) == PCI_BASE_CLASS_BRIDGE)
> + if ((dev->class >> 16) == PCI_BASE_CLASS_BRIDGE) {
> + pci_read_config_word(dev, PCI_COMMAND, &cmd);
> cmd |= PCI_COMMAND_IO | PCI_COMMAND_MEMORY;
> -
> - if (cmd != old_cmd) {
> - printk("PCI: enabling device %s (%04x -> %04x)\n",
> - pci_name(dev), old_cmd, cmd);
> pci_write_config_word(dev, PCI_COMMAND, cmd);
> }
> +
> return 0;
> }
>
> --
> 1.8.2.2
>