linux-kernel - [PATCH v9 11/14] PCI: Use `pcie_wait_for_link_status' in `pcie_wait_for_link

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Message-ID: <alpine.DEB.2.21.2306111611170.64925@angie.orcam.me.uk>
Date:   Sun, 11 Jun 2023 18:19:57 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@...am.me.uk>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
cc:     Alex Williamson <alex.williamson@...hat.com>,
        Lukas Wunner <lukas@...ner.de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Stefan Roese <sr@...x.de>, Jim Wilson <wilson@...iptree.org>,
        David Abdurachmanov <david.abdurachmanov@...il.com>,
        Pali Rohár <pali@...nel.org>,
        linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v9 11/14] PCI: Use `pcie_wait_for_link_status' in
 `pcie_wait_for_link_delay'

Remove a DLLLA status bit polling loop from `pcie_wait_for_link_delay' 
and call almost identical code in `pcie_wait_for_link_status' instead.  
This reduces the lower bound on the polling interval from 10ms to 1ms, 
possibly increasing the CPU load on the system in favour to reducing 
the wait time.

Signed-off-by: Maciej W. Rozycki <macro@...am.me.uk>
---
New change in v9.
---
 drivers/pci/pci.c |   17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

linux-pcie-wait-for-link-delay-status.diff
Index: linux-macro/drivers/pci/pci.c
===================================================================
--- linux-macro.orig/drivers/pci/pci.c
+++ linux-macro/drivers/pci/pci.c
@@ -4889,16 +4889,14 @@ static bool pcie_wait_for_link_status(st
 static bool pcie_wait_for_link_delay(struct pci_dev *pdev, bool active,
 				     int delay)
 {
-	int timeout = PCIE_LINK_RETRAIN_TIMEOUT_MS;
 	bool ret;
-	u16 lnk_status;
 
 	/*
 	 * Some controllers might not implement link active reporting. In this
 	 * case, we wait for 1000 ms + any delay requested by the caller.
 	 */
 	if (!pdev->link_active_reporting) {
-		msleep(timeout + delay);
+		msleep(PCIE_LINK_RETRAIN_TIMEOUT_MS + delay);
 		return true;
 	}
 
@@ -4913,20 +4911,11 @@ static bool pcie_wait_for_link_delay(str
 	 */
 	if (active)
 		msleep(20);
-	for (;;) {
-		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
-		ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
-		if (ret == active)
-			break;
-		if (timeout <= 0)
-			break;
-		msleep(10);
-		timeout -= 10;
-	}
+	ret = pcie_wait_for_link_status(pdev, false, active);
 	if (active && ret)
 		msleep(delay);
 
-	return ret == active;
+	return ret;
 }
 
 /**