[V2,7/7] PCI: make reset poll time adjustable

Introduce pci=resetpolltime= argument to override 60 seconds poll time in
units of milliseconds.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  2 ++
 drivers/pci/pci.c                               | 13 ++++++++-----
 2 files changed, 10 insertions(+), 5 deletions(-)

On Mon, Nov 27, 2017 at 01:20:28AM -0500, Sinan Kaya wrote:
> Introduce pci=resetpolltime= argument to override 60 seconds poll time in
> units of milliseconds.

I resist adding kernel parameters because they really complicate the
user experience.  Obviously you added this for a reason, but I don't
know what that is.  If we really need it, is there any way we could
automatically figure out in the kernel when we need different poll
times?

> Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  2 ++
>  drivers/pci/pci.c                               | 13 ++++++++-----
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 0549662..a07d4f5 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3071,6 +3071,8 @@
>  		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
>  				only look for one device below a PCIe downstream
>  				port.
> +		resetpolltime=	Adjusts the default poll time following hot reset
> +				and D3->D0 transition.
>  
>  	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
>  			Management.
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 8472c24..a6c3e25 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -127,7 +127,7 @@ static int __init pcie_port_pm_setup(char *str)
>  
>  /* time to wait after a reset for device to become responsive */
>  #define PCIE_RESET_READY_POLL_MS 60000
> -
> +static unsigned long pci_reset_polltime = PCIE_RESET_READY_POLL_MS;
>  /**
>   * pci_bus_max_busnr - returns maximum PCI bus number of given bus' children
>   * @bus: pointer to PCI bus structure to search
> @@ -3904,7 +3904,7 @@ int pcie_flr(struct pci_dev *dev)
>  	 */
>  	msleep(100);
>  
> -	return pci_dev_wait(dev, "FLR", PCIE_RESET_READY_POLL_MS);
> +	return pci_dev_wait(dev, "FLR", pci_reset_polltime);
>  }
>  EXPORT_SYMBOL_GPL(pcie_flr);
>  
> @@ -3945,7 +3945,7 @@ static int pci_af_flr(struct pci_dev *dev, int probe)
>  	 */
>  	msleep(100);
>  
> -	return pci_dev_wait(dev, "AF_FLR", PCIE_RESET_READY_POLL_MS);
> +	return pci_dev_wait(dev, "AF_FLR", pci_reset_polltime);
>  }
>  
>  /**
> @@ -3990,7 +3990,7 @@ static int pci_pm_reset(struct pci_dev *dev, int probe)
>  	pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, csr);
>  	pci_dev_d3_sleep(dev);
>  
> -	return pci_dev_wait(dev, "PM D3->D0", PCIE_RESET_READY_POLL_MS);
> +	return pci_dev_wait(dev, "PM D3->D0", pci_reset_polltime);
>  }
>  
>  void pci_reset_secondary_bus(struct pci_dev *dev)
> @@ -4035,7 +4035,7 @@ int pci_reset_bridge_secondary_bus(struct pci_dev *dev)
>  {
>  	pcibios_reset_secondary_bus(dev);
>  
> -	return pci_dev_wait(dev, "bus reset", PCIE_RESET_READY_POLL_MS);
> +	return pci_dev_wait(dev, "bus reset", pci_reset_polltime);
>  }
>  EXPORT_SYMBOL_GPL(pci_reset_bridge_secondary_bus);
>  
> @@ -5528,6 +5528,9 @@ static int __init pci_setup(char *str)
>  				pcie_bus_config = PCIE_BUS_PEER2PEER;
>  			} else if (!strncmp(str, "pcie_scan_all", 13)) {
>  				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
> +			} else if (!strncmp(str, "resetpolltime=", 14)) {
> +				pci_reset_polltime =
> +					simple_strtoul(str + 14, &str, 0);
>  			} else {
>  				printk(KERN_ERR "PCI: Unknown option `%s'\n",
>  						str);
> -- 
> 1.9.1
>

On 11/28/2017 9:20 AM, Bjorn Helgaas wrote:
>> Introduce pci=resetpolltime= argument to override 60 seconds poll time in
>> units of milliseconds.
> I resist adding kernel parameters because they really complicate the
> user experience.  Obviously you added this for a reason, but I don't
> know what that is.  If we really need it, is there any way we could
> automatically figure out in the kernel when we need different poll
> times?
> 

No, we can drop this patch if we want to . This was mostly a
scalability concern. 

I worried adding 60 seconds would be too much for some use case. We can
hold onto this change until that use case happens if you want.