[PATCH] Use maximum latency when determining L1/L0s ASPM v2

[Ian Kumlien <ian.kumlien@gmail.com>]

Changes:
* Handle L0s correclty as well, making it per direction
* Moved the switch cost in to the if statement since a non L1 switch has
  no additional cost.

For L0s:
We sumarize the entire latency per direction to see if it's acceptable
for the PCIe endpoint.

If it's not, we clear the link for the path that had too large latency.

For L1:
Currently we check the maximum latency of upstream and downstream
per link, not the maximum for the path

This would work if all links have the same latency, but:
endpoint -> c -> b -> a -> root  (in the order we walk the path)

If c or b has the higest latency, it will not register

Fix this by maintaining the maximum latency value for the path

This change fixes a regression introduced (but not caused) by:
66ff14e59e8a (PCI/ASPM: Allow ASPM on links to PCIe-to-PCI/PCI-X Bridges)

Signed-off-by: Ian Kumlien <ian.kumlien@gmail.com>
---
 drivers/pci/pcie/aspm.c | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index b17e5ffd31b1..bc512e217258 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -434,7 +434,8 @@ static void pcie_get_aspm_reg(struct pci_dev *pdev,
 
 static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 {
-	u32 latency, l1_switch_latency = 0;
+	u32 latency, l1_max_latency = 0, l1_switch_latency = 0,
+		l0s_latency_up = 0, l0s_latency_dw = 0;
 	struct aspm_latency *acceptable;
 	struct pcie_link_state *link;
 
@@ -447,15 +448,22 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 	acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];
 
 	while (link) {
-		/* Check upstream direction L0s latency */
-		if ((link->aspm_capable & ASPM_STATE_L0S_UP) &&
-		    (link->latency_up.l0s > acceptable->l0s))
-			link->aspm_capable &= ~ASPM_STATE_L0S_UP;
-
-		/* Check downstream direction L0s latency */
-		if ((link->aspm_capable & ASPM_STATE_L0S_DW) &&
-		    (link->latency_dw.l0s > acceptable->l0s))
-			link->aspm_capable &= ~ASPM_STATE_L0S_DW;
+		if (link->aspm_capable & ASPM_STATE_L0S) {
+			/* Check upstream direction L0s latency */
+			if (link->aspm_capable & ASPM_STATE_L0S_UP) {
+				l0s_latency_up += link->latency_up.l0s;
+				if (l0s_latency_up > acceptable->l0s)
+					link->aspm_capable &= ~ASPM_STATE_L0S_UP;
+			}
+
+			/* Check downstream direction L0s latency */
+			if (link->aspm_capable & ASPM_STATE_L0S_DW) {
+				l0s_latency_dw += link->latency_dw.l0s;
+				if (l0s_latency_dw > acceptable->l0s)
+					link->aspm_capable &= ~ASPM_STATE_L0S_DW;
+			}
+		}
+
 		/*
 		 * Check L1 latency.
 		 * Every switch on the path to root complex need 1
@@ -469,11 +477,14 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 		 * L1 exit latencies advertised by a device include L1
 		 * substate latencies (and hence do not do any check).
 		 */
-		latency = max_t(u32, link->latency_up.l1, link->latency_dw.l1);
-		if ((link->aspm_capable & ASPM_STATE_L1) &&
-		    (latency + l1_switch_latency > acceptable->l1))
-			link->aspm_capable &= ~ASPM_STATE_L1;
-		l1_switch_latency += 1000;
+		if (link->aspm_capable & ASPM_STATE_L1) {
+			latency = max_t(u32, link->latency_up.l1, link->latency_dw.l1);
+			l1_max_latency = max_t(u32, latency, l1_max_latency);
+			if (l1_max_latency + l1_switch_latency > acceptable->l1)
+				link->aspm_capable &= ~ASPM_STATE_L1;
+
+			l1_switch_latency += 1000;
+		}
 
 		link = link->parent;
 	}
-- 
2.28.0