linux-kernel - [PATCH v2 7/7] PCI/DPC: Replace msleep(10) with usleep

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Message-Id: <20250822155908.625553-8-18255117159@163.com>
Date: Fri, 22 Aug 2025 23:59:08 +0800
From: Hans Zhang <18255117159@....com>
To: bhelgaas@...gle.com,
	helgaas@...nel.org,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Hans Zhang <18255117159@....com>
Subject: [PATCH v2 7/7] PCI/DPC: Replace msleep(10) with usleep_range() for precise RP busy checking

The msleep(10) in dpc_wait_rp_inactive() may sleep longer than intended
due to timer granularity, which can cause unnecessary delays in downstream
port containment recovery. Replace it with usleep_range() for a more
precise delay of approximately 10ms.

Signed-off-by: Hans Zhang <18255117159@....com>
---
 drivers/pci/pcie/dpc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index fc18349614d7..ff0884d669b7 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -21,6 +21,8 @@
 #define PCI_EXP_DPC_CTL_EN_MASK	(PCI_EXP_DPC_CTL_EN_FATAL | \
 				 PCI_EXP_DPC_CTL_EN_NONFATAL)
 
+#define PCIE_EXP_DPC_BUSY_CHECK_US	10000
+
 static const char * const rp_pio_error_string[] = {
 	"Configuration Request received UR Completion",	 /* Bit Position 0  */
 	"Configuration Request received CA Completion",	 /* Bit Position 1  */
@@ -135,7 +137,8 @@ static int dpc_wait_rp_inactive(struct pci_dev *pdev)
 	pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
 	while (status & PCI_EXP_DPC_RP_BUSY &&
 					!time_after(jiffies, timeout)) {
-		msleep(10);
+		usleep_range(PCIE_EXP_DPC_BUSY_CHECK_US,
+			     PCIE_EXP_DPC_BUSY_CHECK_US + 100);
 		pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
 	}
 	if (status & PCI_EXP_DPC_RP_BUSY) {
-- 
2.25.1