linux-kernel - [PATCH v3] PCI: aardvark: Don't rely on jiffies while holding spinlock

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Message-Id: <20190927085502.1758-1-repk@triplefau.lt>
Date:   Fri, 27 Sep 2019 10:55:02 +0200
From:   Remi Pommarel <repk@...plefau.lt>
To:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Remi Pommarel <repk@...plefau.lt>
Subject: [PATCH v3] PCI: aardvark: Don't rely on jiffies while holding spinlock

advk_pcie_wait_pio() can be called while holding a spinlock (from
pci_bus_read_config_dword()), then depends on jiffies in order to
timeout while polling on PIO state registers. In the case the PIO
transaction failed, the timeout will never happen and will also cause
the cpu to stall.

This decrements a variable and wait instead of using jiffies.

Signed-off-by: Remi Pommarel <repk@...plefau.lt>
---
Changes since v1:
  - Reduce polling delay
  - Change size_t into int for loop counter
Changes since v2:
  - Keep timeout to 1ms by increasing retry counter
---
 drivers/pci/controller/pci-aardvark.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index fc0fe4d4de49..7b5c9d6c8706 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -175,7 +175,8 @@
 	(PCIE_CONF_BUS(bus) | PCIE_CONF_DEV(PCI_SLOT(devfn))	| \
 	 PCIE_CONF_FUNC(PCI_FUNC(devfn)) | PCIE_CONF_REG(where))
 
-#define PIO_TIMEOUT_MS			1
+#define PIO_RETRY_CNT			500
+#define PIO_RETRY_DELAY			2 /* 2 us*/
 
 #define LINK_WAIT_MAX_RETRIES		10
 #define LINK_WAIT_USLEEP_MIN		90000
@@ -383,17 +384,16 @@ static void advk_pcie_check_pio_status(struct advk_pcie *pcie)
 static int advk_pcie_wait_pio(struct advk_pcie *pcie)
 {
 	struct device *dev = &pcie->pdev->dev;
-	unsigned long timeout;
+	int i;
 
-	timeout = jiffies + msecs_to_jiffies(PIO_TIMEOUT_MS);
-
-	while (time_before(jiffies, timeout)) {
+	for (i = 0; i < PIO_RETRY_CNT; i++) {
 		u32 start, isr;
 
 		start = advk_readl(pcie, PIO_START);
 		isr = advk_readl(pcie, PIO_ISR);
 		if (!start && isr)
 			return 0;
+		udelay(PIO_RETRY_DELAY);
 	}
 
 	dev_err(dev, "config read/write timed out\n");
-- 
2.20.1