2019-09-27 08:49:45

by Remi Pommarel

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 <[email protected]>
---
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

2019-09-27 09:46:40

by Thomas Petazzoni

Subject: Re: [PATCH v3] PCI: aardvark: Don't rely on jiffies while holding spinlock

On Fri, 27 Sep 2019 10:55:02 +0200
Remi Pommarel <[email protected]> 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 <[email protected]>

Acked-by: Thomas Petazzoni <[email protected]>

Thanks!

Thomas
--
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

2019-09-30 14:51:10

by Andrew Murray

Subject: Re: [PATCH v3] PCI: aardvark: Don't rely on jiffies while holding spinlock

On Fri, Sep 27, 2019 at 11:45:55AM +0200, Thomas Petazzoni wrote:
> On Fri, 27 Sep 2019 10:55:02 +0200
> Remi Pommarel <[email protected]> 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 <[email protected]>
>
> Acked-by: Thomas Petazzoni <[email protected]>
>

Reviewed-by: Andrew Murray <[email protected]>

> Thanks!
>
> Thomas
> --
> Thomas Petazzoni, CTO, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

2019-10-15 12:12:31

by Lorenzo Pieralisi

Subject: Re: [PATCH v3] PCI: aardvark: Don't rely on jiffies while holding spinlock

On Fri, Sep 27, 2019 at 10:55:02AM +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 <[email protected]>
> ---
> 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(-)

Applied to pci/aardvark, thanks.

Lorenzo

> 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
>