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From: Ian Kumlien <ian.kumlien@gmail.com>
To: linux-pci@vger.kernel.org
Cc: Ian Kumlien <ian.kumlien@gmail.com>
Subject: [PATCH] Use maximum latency when determining L1 ASPM
Date: Mon, 27 Jul 2020 23:30:45 +0200
Message-ID: <20200727213045.2117855-1-ian.kumlien@gmail.com> (raw)

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 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 | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index b17e5ffd31b1..bd53fba7f382 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -434,7 +434,7 @@ 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;
 	struct aspm_latency *acceptable;
 	struct pcie_link_state *link;
 
@@ -470,8 +470,9 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 		 * substate latencies (and hence do not do any check).
 		 */
 		latency = max_t(u32, link->latency_up.l1, link->latency_dw.l1);
+		l1_max_latency = max_t(u32, latency, l1_max_latency);
 		if ((link->aspm_capable & ASPM_STATE_L1) &&
-		    (latency + l1_switch_latency > acceptable->l1))
+		    (l1_max_latency + l1_switch_latency > acceptable->l1))
 			link->aspm_capable &= ~ASPM_STATE_L1;
 		l1_switch_latency += 1000;
 
-- 
2.27.0


             reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27 21:30 Ian Kumlien [this message]
2020-07-29 22:27 ` Bjorn Helgaas
2020-07-29 22:43   ` Ian Kumlien
2020-08-03 14:58   ` [PATCH] Use maximum latency when determining L1/L0s ASPM v2 Ian Kumlien
  -- strict thread matches above, loose matches on Subject: below --
2020-07-26 22:06 [PATCH] Use maximum latency when determining L1 ASPM Ian Kumlien
2020-07-26 22:06 ` Ian Kumlien
2020-07-27 21:17   ` Ian Kumlien

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