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

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

[Remi Pommarel]

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>
---
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

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

[Thomas Petazzoni]

On Fri, 27 Sep 2019 10:55:02 +0200
Remi Pommarel <repk@triplefau.lt> 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>

Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Thanks!

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

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

[Andrew Murray]

On Fri, Sep 27, 2019 at 11:45:55AM +0200, Thomas Petazzoni wrote:
> On Fri, 27 Sep 2019 10:55:02 +0200
> Remi Pommarel <repk@triplefau.lt> 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>
> 
> Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
> 

Reviewed-by: Andrew Murray <andrew.murray@arm.com>

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

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

[Lorenzo Pieralisi]

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 <repk@triplefau.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(-)

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
>