[v8,4/6] PCI: Allow extend_bridge_window() to shrink resource if necessary
diff mbox series

Message ID SL2P216MB01879766498AA7746C2E5FB780C00@SL2P216MB0187.KORP216.PROD.OUTLOOK.COM
State New
Delegated to: Bjorn Helgaas
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Series
  • Patch series to support Thunderbolt without any BIOS support
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Commit Message

Nicholas Johnson July 26, 2019, 12:54 p.m. UTC
Remove checks for resource size in extend_bridge_window(). This is
necessary to allow the pci_bus_distribute_available_resources() to
function when the kernel parameter pci=hpmemsize=nn[KMG] is used to
allocate resources. Because the kernel parameter sets the size of all
hotplug bridges to be the same, there are problems when nested hotplug
bridges are encountered. Fitting a downstream hotplug bridge with size X
and normal bridges with size Y into parent hotplug bridge with size X is
impossible, and hence the downstream hotplug bridge needs to shrink to
fit into its parent.

Add check for if bridge is extended or shrunken and adjust pci_dbg to
reflect this.

Reset the resource if its new size is zero (if we have run out of a
bridge window resource). If it is set to zero size and left, it can
cause significant problems when it comes to enabling devices.

Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
---
 drivers/pci/setup-bus.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

Comments

Mika Westerberg Oct. 8, 2019, 12:09 p.m. UTC | #1
On Fri, Jul 26, 2019 at 12:54:22PM +0000, Nicholas Johnson wrote:
> Remove checks for resource size in extend_bridge_window(). This is
> necessary to allow the pci_bus_distribute_available_resources() to
> function when the kernel parameter pci=hpmemsize=nn[KMG] is used to
> allocate resources. Because the kernel parameter sets the size of all
> hotplug bridges to be the same, there are problems when nested hotplug
> bridges are encountered. Fitting a downstream hotplug bridge with size X
> and normal bridges with size Y into parent hotplug bridge with size X is
> impossible, and hence the downstream hotplug bridge needs to shrink to
> fit into its parent.

Maybe you could show the topology here which needs shrinking.

> Add check for if bridge is extended or shrunken and adjust pci_dbg to
> reflect this.
> 
> Reset the resource if its new size is zero (if we have run out of a
> bridge window resource). If it is set to zero size and left, it can
> cause significant problems when it comes to enabling devices.

Same comment here about explaining the "significant problems".
> 
> Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
> ---
>  drivers/pci/setup-bus.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index a072781ab..7e1dc892a 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1823,13 +1823,19 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,

Since it is also shrinking now maybe name it adjust_bridge_window() instead?

Patch
diff mbox series

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index a072781ab..7e1dc892a 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1823,13 +1823,19 @@  static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
 	if (res->parent)
 		return;
 
-	if (resource_size(res) >= new_size)
-		return;
-
-	add_size = new_size - resource_size(res);
-	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res, &add_size);
+	if (new_size > resource_size(res)) {
+		add_size = new_size - resource_size(res);
+		pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
+			&add_size);
+	} else if (new_size < resource_size(res)) {
+		add_size = resource_size(res) - new_size;
+		pci_dbg(bridge, "bridge window %pR shrunken by %pa\n", res,
+			&add_size);
+	}
 	res->end = res->start + new_size - 1;
 	remove_from_list(add_list, res);
+	if (!new_size)
+		reset_resource(res);
 }
 
 static void pci_bus_distribute_available_resources(struct pci_bus *bus,