Re: [ACPI] [Proposal]Another way to save/restore PCI config space forsuspend/resume

[Hiroshi 2 Itoh]

Hi,

acpi-devel-admin@xxxxxxxxxxxxxxxxxxxxx wrote on 2004/10/26 13:50:57:

> Hi,
> We suffer from PCI config space issue for a long time, which causes many
> system can't correctly resume. Current Linux mechanism isn't sufficient.
> Here is a another idea:
> Record all PCI writes in Linux kernel, and redo all the write after
> resume in order. The idea assumes Firmware will restore all PCI config
> space to the boot time state, which is true at least for IA32.
>

I think a basic problem of current Linux device model is that there is no
effective message path from sibling devices to their root device.
Although the message direction from a root device to sibling devices is
natural from the viewpoint of device enumeration, the direction from
sibling devices to a root device is required for effective arbitration for
device configuration and power management.

The Windows driver model uses the direction from sibling drivers to a root
bus driver mainly, i.e. sibling drivers are layered on a root bus driver.
While we need a kind of callback mechanism from PCI (sibling) devices to
PCI bus (root) device instead because their normal call interface is from a
root device to sibling devices.

- Hiro.

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