[PATCH v10 08/18] PCI/P2PDMA: Route Relaxed Ordering Completions directly

[Leon Romanovsky]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

ACS P2P Completion Redirect leaves Completions carrying the Relaxed
Ordering attribute alone. PCIe r7.0 sec 6.12.1.1 redirects only those "that
do not have the Relaxed Ordering Attribute bit set", and sec 7.7.12.5
describes the enable bit as "applicable only to Completions whose Relaxed
Ordering Attribute is clear". P2PDMA reports one answer for every kind of
TLP, so a client that sets Relaxed Ordering on its Non-Posted Requests,
and therefore receives such Completions (sec 2.2.9.1), is sent through
the host bridge for a redirect that never happens to it.

Route Completions directly for the classes that set
PCI_P2PDMA_TLP_RELAXED_CPL.

Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Tested-by: Tushar Dave <tdave@xxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
 drivers/pci/p2pdma.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 479bf58104ca..e6482467e121 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -542,11 +542,15 @@ pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags)
 /*
  * Decide how a peer-to-peer Completion at an ACS-capable ingress port routes.
  * PCIe r7.0 sec 6.12.1.1: no ACS control other than P2P Completion Redirect
- * affects a Completion.
+ * affects a Completion, and that one leaves Completions carrying the Relaxed
+ * Ordering attribute alone.
  */
 static enum pci_acs_p2pdma_state
 pci_acs_p2pdma_completion(u16 ctrl, unsigned int tlp_flags)
 {
+	if (tlp_flags & PCI_P2PDMA_TLP_RELAXED_CPL)
+		return PCI_ACS_P2PDMA_DIRECT;
+
 	return ctrl & PCI_ACS_CR ? PCI_ACS_P2PDMA_REDIRECT :
 				   PCI_ACS_P2PDMA_DIRECT;
 }

-- 
2.55.0