linux-kernel - [PATCH v9 08/14] PCI: Use distinct local vars in `pcie_retrain

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Message-ID: <alpine.DEB.2.21.2306110252260.64925@angie.orcam.me.uk>
Date:   Sun, 11 Jun 2023 18:19:45 +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 08/14] PCI: Use distinct local vars in
 `pcie_retrain_link'

Use separate local variables to hold the respective values retrieved 
from the Link Control Register and the Link Status Register.  Not only 
it improves readability, but it makes it possible for the compiler to 
detect actual uninitialised use should this code change in the future.

Signed-off-by: Maciej W. Rozycki <macro@...am.me.uk>
---
New change in v9.
---
 drivers/pci/pci.c |   19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

linux-pcie-retrain-link-lnkctl-lnksta.diff
Index: linux-macro/drivers/pci/pci.c
===================================================================
--- linux-macro.orig/drivers/pci/pci.c
+++ linux-macro/drivers/pci/pci.c
@@ -4922,30 +4922,31 @@ bool pcie_wait_for_link(struct pci_dev *
 bool pcie_retrain_link(struct pci_dev *pdev)
 {
 	unsigned long end_jiffies;
-	u16 reg16;
+	u16 lnkctl;
+	u16 lnksta;
 
-	pcie_capability_read_word(pdev, PCI_EXP_LNKCTL, &reg16);
-	reg16 |= PCI_EXP_LNKCTL_RL;
-	pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, reg16);
+	pcie_capability_read_word(pdev, PCI_EXP_LNKCTL, &lnkctl);
+	lnkctl |= PCI_EXP_LNKCTL_RL;
+	pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, lnkctl);
 	if (pdev->clear_retrain_link) {
 		/*
 		 * Due to an erratum in some devices the Retrain Link bit
 		 * needs to be cleared again manually to allow the link
 		 * training to succeed.
 		 */
-		reg16 &= ~PCI_EXP_LNKCTL_RL;
-		pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, reg16);
+		lnkctl &= ~PCI_EXP_LNKCTL_RL;
+		pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, lnkctl);
 	}
 
 	/* Wait for link training end. Break out after waiting for timeout. */
 	end_jiffies = jiffies + msecs_to_jiffies(PCIE_LINK_RETRAIN_TIMEOUT_MS);
 	do {
-		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &reg16);
-		if (!(reg16 & PCI_EXP_LNKSTA_LT))
+		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta);
+		if (!(lnksta & PCI_EXP_LNKSTA_LT))
 			break;
 		msleep(1);
 	} while (time_before(jiffies, end_jiffies));
-	return !(reg16 & PCI_EXP_LNKSTA_LT);
+	return !(lnksta & PCI_EXP_LNKSTA_LT);
 }
 
 /*