linux-kernel - [PATCH v2 03/17] PCI: dwc: Add more verbose link-up message

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Date:   Wed, 4 May 2022 00:46:24 +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 v2 03/17] 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>

---

Changelog v2:
- Test the error condition first and return straight away if it comes true.
  The typical return is better to be unindented (@Joe).
---
 drivers/pci/controller/dwc/pcie-designware.c | 22 ++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 6e81264fdfb4..1682f477bf20 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -524,20 +524,30 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, int index,
 
 int dw_pcie_wait_for_link(struct dw_pcie *pci)
 {
+	u32 offset, val;
 	int retries;
 
 	/* 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) {
+		dev_err(pci->dev, "Phy link never came up\n");
+		return -ETIMEDOUT;
+	}
+
+	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
 
-	return -ETIMEDOUT;
+	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;
 }
 EXPORT_SYMBOL_GPL(dw_pcie_wait_for_link);
 
-- 
2.35.1