linux-kernel - [PATCH 03/16] PCI: dwc: Add more verbose link-up message

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Message-ID: <20220324013734.18234-4-Sergey.Semin@baikalelectronics.ru>
Date:   Thu, 24 Mar 2022 04:37:21 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>
CC:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 03/16] PCI: dwc: Add more verbose link-up message

Printing just "link up" isn't that much informative especially when it
comes to working with the PCI Express bus. Even if the link is up, due to
multiple reasons the bus performance can degrade to slower speeds or to
narrower width than both Root Port and its partner is capable of. In that
case it would be handy to know the link specifications as early as
possible. So let's add a more verbose message to the busy-wait link-state
method, which will contain the link speed generation and the PCIe bus
width in case if the link up state is discovered. Otherwise an error will
be printed to the system log.

Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
---
 drivers/pci/controller/dwc/pcie-designware.c | 22 +++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 6e81264fdfb4..f1693e25afcb 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -528,14 +528,26 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
 
 	/* Check if the link is up or not */
 	for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
-		if (dw_pcie_link_up(pci)) {
-			dev_info(pci->dev, "Link up\n");
-			return 0;
-		}
+		if (dw_pcie_link_up(pci))
+			break;
+
 		usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
 	}
 
-	dev_info(pci->dev, "Phy link never came up\n");
+	if (retries < LINK_WAIT_MAX_RETRIES) {
+		u32 offset, val;
+
+		offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+		val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
+
+		dev_info(pci->dev, "PCIe Gen.%u x%u link up\n",
+			 FIELD_GET(PCI_EXP_LNKSTA_CLS, val),
+			 FIELD_GET(PCI_EXP_LNKSTA_NLW, val));
+
+		return 0;
+	}
+
+	dev_err(pci->dev, "Phy link never came up\n");
 
 	return -ETIMEDOUT;
 }
-- 
2.35.1