forked from Minki/linux
448e2ca0e3
There are hardware limitations on the number of available MSIs, which firmware expresses using a property named "ibm,pe-total-#msi". This property tells us how many MSIs are available for devices below the point in the PCI tree where we find the property. For old firmwares which don't have the property, we assume there are 8 MSIs available per "partitionable endpoint" (PE). The PE can be found using existing EEH code, which uses the methods described in PAPR. For our purposes we want the parent of the node that's identified using this method. When a driver requests n MSIs for a device, we first establish where the "ibm,pe-total-#msi" property above that device is, or we find the PE if the property is not found. In both cases we call this node the "pe_dn". We then count all non-bridge devices below the pe_dn, to establish how many devices in total may need MSIs. The quota is then simply the total available divided by the number of devices, if the request is less than or equal to the quota, the request is fine and we're done. If the request is greater than the quota, we try to determine if there are any "spare" MSIs which we can give to this device. Spare MSIs are found by looking for other devices which can never use their full quota, because their "req#msi(-x)" property is less than the quota. If we find any spare, we divide the spares by the number of devices that could request more than their quota. This ensures the spare MSIs are spread evenly amongst all over-quota requestors. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
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| boot | ||
| configs | ||
| include/asm | ||
| kernel | ||
| kvm | ||
| lib | ||
| math-emu | ||
| mm | ||
| oprofile | ||
| platforms | ||
| sysdev | ||
| xmon | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||