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SubjectRe: [PATCH v1 3/3] PCI: Consider alignment of hot-added bridges when distributing available resources
On Mon, Jan 06, 2020 at 03:46:13PM +0000, Nicholas Johnson wrote:
> Change pci_bus_distribute_available_resources() to better handle bridges
> with different resource alignment requirements.
>
> The arguments io, mmio and mmio_pref represent the start and end
> addresses of resource, in which we must fit the current bridge window.
>
> The steps taken by pci_bus_distribute_available_resources():
>
> - For io, mmio and mmio_pref, increase .start to align with the
> alignment of the current bridge window (otherwise the current
> bridge window may not fit within the available range).
>
> - For io, mmio and mmio_pref, adjust the current bridge window
> to the size after the above.
>
> - Count the number of hotplug bridges and normal bridges on this
> bus.
>
> - If the total number of bridges is one, give that bridge all of
> the resources and return.
>
> - If there are no hotplug bridges, return.
>
> - For io, mmio and mmio_pref, increase .start by the amount
> required for each bridge resource on the bus for non hotplug
> bridges, giving extra room to make up for alignment of those
> resources.
>
> - For io, mmio and mmio_pref, calculate the resource size per
> hotplug bridge which is available after the previous steps.
>
> - For io, mmio and mmio_pref, distribute the resources to each
> hotplug bridge, with the sizes calculated above.
>
> The motivation for fixing this is Thunderbolt with native PCI
> enumeration, enabling external graphics cards and other devices with
> bridge alignment higher than 1MB. This fixes the use case where the user
> hot-adds Thunderbolt devices containing PCI devices with BAR
> alignment >1M and having the resources fail to assign.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=199581
> Reported-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Still solves the issue I reported above so,

Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Also looks good to me,

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

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