On Wed, Mar 19, 2014 at 9:03 PM, Zhang, Rui <rui.zhang@xxxxxxxxx> wrote: > I've talked with Yan Zheng, and I was told that this resource "0xfed10000 - 0xfed15fff" > is got from PCI device register directly, which is not in its BAR range. > Thus IMO, it is impossible for PNP layer to be aware of this resource. Slow down, this isn't quite correct. The *base* address (0xfed10000) is from a PCI config register (MCHBAR, at PCI config offset 0x48) [1]. This is a device-dependent register, so the PCI core knows neither the base nor the size. The device consumes address space that is not reported via the architected PCI mechanism, so the only way to report that space is via the PNP0C02 ACPI device. The BIOS has to determine the base and size based on its knowledge of the hardware. On this hardware, per the spec in [1], the region described by MCHBAR is 32KB in size. The 0x6000 (24KB) size of the region above comes from the driver and is actually less than what the device consumes. It is legal for a driver to request only the area it requires, but the entire area consumed by the device should be reported via the PNP0C02 device. The fact that PNP0C02 reports 16KB but the device actually consumes 32KB is a BIOS defect. This probably happened because previous versions of this chip consumed only 16KB, and the BIOS didn't get updated for the change. > BTW, about drivers/pnp/system.c, if its ONLY purpose is to prevent those > resources from being allocated to uninitialized PCI devices, then IMO, > the best way to do this is make PCI bus handle those PNP0C01/PNP0C02 > resources directly, probably via a platform callback, say, > 1. make drivers/pnp/system.c a no-op for PNPACPI, by checking pnp_dev->protocol. > 2. introduce acpi_check_reserved_resource() to parsing PNP0C01/PNP0C02 resources. > 3. in PCI bus, invoke acpi_check_reserved_resource() when assigning > resources to PCI devices. The purpose of system.c is indeed to prevent resources from being allocated to other devices. This is really a question for Rafael, but in my opinion this function (reserving resources of PNP/ACPI devices to prevent their allocation to other devices) should be done for *all* PNP and ACPI devices, not just the PNP0C01/PNP0C02 devices handled by system.c. So I think the best solution would be to move that into the ACPI core somehow so it happens for all devices. If we had that, we could get rid of system.c altogether, and we wouldn't have to do anything special in PCI. This is much easier to say than to do, however, because there are all kinds of issues with legacy resource reservations, and we currently can't really deal with overlapping resources. Bjorn [1] https://www-ssl.intel.com/content/www/us/en/processors/core/4th-gen-core-family-desktop-vol-2-datasheet, sec. 3.1.2 on p. 61 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
