From: Andrew Murray <andrew.murray@arm.com>
To: Remi Pommarel <repk@triplefau.lt>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Bjorn Helgaas <bhelgaas@google.com>,
linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PCI: aardvark: Don't rely on jiffies while holding spinlock
Date: Mon, 2 Sep 2019 11:50:56 +0100 [thread overview]
Message-ID: <20190902105056.GF9720@e119886-lin.cambridge.arm.com> (raw)
In-Reply-To: <20190901142303.27815-1-repk@triplefau.lt>
On Sun, Sep 01, 2019 at 04:23:03PM +0200, Remi Pommarel wrote:
> 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@triplefau.lt>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
> ---
> 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..1fa6d04ad7aa 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 10
> +#define PIO_RETRY_DELAY 100 /* 100 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;
> + size_t 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
>
next prev parent reply other threads:[~2019-09-02 10:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-01 14:23 [PATCH] PCI: aardvark: Don't rely on jiffies while holding spinlock Remi Pommarel
2019-09-02 10:06 ` Lorenzo Pieralisi
2019-09-02 10:50 ` Andrew Murray [this message]
2019-09-25 9:33 ` Thomas Petazzoni
2019-09-27 8:25 ` Remi Pommarel
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