Re: [PATCH v2 1/2] net: make driver settling time configurable

[Denis Kirjanov]

On 2/8/24 12:52, David Ventura wrote:
> During IP auto configuration, some drivers apparently need to wait a
> certain length of time to settle; as this is not true for all drivers,
> make this length of time configurable.
> 
> Signed-off-by: David Ventura <david@xxxxxxxxxx>
> ---
>  .../admin-guide/kernel-parameters.txt         |  4 ++++
>  Documentation/admin-guide/nfs/nfsroot.rst     |  3 +++
>  net/ipv4/ipconfig.c                           | 23 ++++++++++++++++---
>  3 files changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index b47940577c10..b07a035642fa 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2291,6 +2291,10 @@
>  
>  	ip=		[IP_PNP]
>  			See Documentation/admin-guide/nfs/nfsroot.rst.
> +	ip.dev_wait_ms=
> +			[IP_PNP]
> +			See Documentation/admin-guide/nfs/nfsroot.rst.
> +
>  
>  	ipcmni_extend	[KNL,EARLY] Extend the maximum number of unique System V
>  			IPC identifiers from 32,768 to 16,777,216.
> diff --git a/Documentation/admin-guide/nfs/nfsroot.rst b/Documentation/admin-guide/nfs/nfsroot.rst
> index 135218f33394..f26f7a342af6 100644
> --- a/Documentation/admin-guide/nfs/nfsroot.rst
> +++ b/Documentation/admin-guide/nfs/nfsroot.rst
> @@ -223,6 +223,9 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:<dns
>    /proc/net/ipconfig/ntp_servers to an NTP client before mounting the real
>    root filesystem if it is on NFS).
>  
> +ip.dev_wait_ms=<value>
> +  Set the number of milliseconds to delay after opening the network device
> +  which will be autoconfigured. Defaults to 10 milliseconds.
>  
>  nfsrootdebug
>    This parameter enables debugging messages to appear in the kernel
> diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
> index c56b6fe6f0d7..cbf35163b973 100644
> --- a/net/ipv4/ipconfig.c
> +++ b/net/ipv4/ipconfig.c
> @@ -82,8 +82,6 @@
>  #define IPCONFIG_DYNAMIC
>  #endif
>  
> -/* Define the friendly delay before and after opening net devices */
> -#define CONF_POST_OPEN		10	/* After opening: 10 msecs */
>  
>  /* Define the timeout for waiting for a DHCP/BOOTP/RARP reply */
>  #define CONF_OPEN_RETRIES 	2	/* (Re)open devices twice */
> @@ -101,6 +99,7 @@
>  
>  /* Wait for carrier timeout default in seconds */
>  static unsigned int carrier_timeout = 120;
> +static unsigned int dev_wait_ms = 10;
>  
>  /*
>   * Public IP configuration
> @@ -1516,7 +1515,8 @@ static int __init ip_auto_config(void)
>  		return err;
>  
>  	/* Give drivers a chance to settle */
> -	msleep(CONF_POST_OPEN);
> +	if(dev_wait_ms > 0)
> +		msleep(dev_wait_ms);

What's the point to wait more than CONF_POST_OPEN with the change?

>  
>  	/*
>  	 * If the config information is insufficient (e.g., our IP address or
> @@ -1849,3 +1849,20 @@ static int __init set_carrier_timeout(char *str)
>  	return 1;
>  }
>  __setup("carrier_timeout=", set_carrier_timeout);
> +
> +
> +static int __init set_dev_wait_ms(char *str)
> +{
> +	ssize_t ret;
> +
> +	if (!str)
> +		return 0;
> +
> +	ret = kstrtouint(str, 0, &dev_wait_ms);
> +	if (ret)
> +		return 0;
> +
> +	return 1;
> +}
> +
> +__setup("ip.dev_wait_ms=", set_dev_wait_ms);