netdev - Re: [PATCH 1/5] NetXen: Fix softlock seen on some machines during hardware writes

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Date:	Tue, 13 Mar 2007 17:29:17 +0530
From:	Mithlesh Thukral <mithlesh@...xen.com>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
Cc:	netdev@...r.kernel.org, amitkale@...xen.com, jeff@...zik.org,
	netxenproj@...syssoft.com, rob@...xen.com
Subject: Re: [PATCH 1/5] NetXen: Fix softlock seen on some machines during hardware writes

On Friday 09 March 2007 21:56, Stephen Hemminger wrote:
> Linsys Contractor Mithlesh Thukral wrote:
> > NetXen: This will fix a softlock seen on some machines.
> > The reason was too much time was spent waiting for writes to go through.
> >
> > Signed-off by: Mithlesh Thukral <mithlesh@...xen.com>
> > ---
> >  drivers/net/netxen/netxen_nic.h         |    1 +
> >  drivers/net/netxen/netxen_nic_ethtool.c |    1 +
> >  drivers/net/netxen/netxen_nic_init.c    |   11 +++++++++--
> >  3 files changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/netxen/netxen_nic.h
> > b/drivers/net/netxen/netxen_nic.h index 38d7409..c85c2cb 100644
> > --- a/drivers/net/netxen/netxen_nic.h
> > +++ b/drivers/net/netxen/netxen_nic.h
> > @@ -236,6 +236,7 @@ #define MPORT_MULTI_FUNCTION_MODE 0x2222
> >
> >  #include "netxen_nic_phan_reg.h"
> >  extern unsigned long long netxen_dma_mask;
> > +extern unsigned long last_schedule_time;
> >
> >  /*
> >   * NetXen host-peg signal message structure
> > diff --git a/drivers/net/netxen/netxen_nic_ethtool.c
> > b/drivers/net/netxen/netxen_nic_ethtool.c index 3752d2a..d49a7d8 100644
> > --- a/drivers/net/netxen/netxen_nic_ethtool.c
> > +++ b/drivers/net/netxen/netxen_nic_ethtool.c
> > @@ -455,6 +455,7 @@ netxen_nic_set_eeprom(struct net_device
> >  		}
> >  		printk(KERN_INFO "%s: flash unlocked. \n",
> >  			netxen_nic_driver_name);
> > +		last_schedule_time = jiffies;
> >  		ret = netxen_flash_erase_secondary(adapter);
> >  		if (ret != FLASH_SUCCESS) {
> >  			printk(KERN_ERR "%s: Flash erase failed.\n",
> > diff --git a/drivers/net/netxen/netxen_nic_init.c
> > b/drivers/net/netxen/netxen_nic_init.c index b2e776f..53ca21e 100644
> > --- a/drivers/net/netxen/netxen_nic_init.c
> > +++ b/drivers/net/netxen/netxen_nic_init.c
> > @@ -42,6 +42,8 @@ struct crb_addr_pair {
> >  	u32 data;
> >  };
> >
> > +unsigned long last_schedule_time;
> > +
> >  #define NETXEN_MAX_CRB_XFORM 60
> >  static unsigned int crb_addr_xform[NETXEN_MAX_CRB_XFORM];
> >  #define NETXEN_ADDR_ERROR (0xffffffff)
> > @@ -404,9 +406,14 @@ static inline int do_rom_fast_write(stru
> >  static inline int
> >  do_rom_fast_read(struct netxen_adapter *adapter, int addr, int *valp)
> >  {
> > +	if (jiffies > (last_schedule_time + (8 * HZ))) {
> > +		last_schedule_time = jiffies;
> > +		schedule();
> > +	}
> > +
> >  	netxen_nic_reg_write(adapter, NETXEN_ROMUSB_ROM_ADDRESS, addr);
> >  	netxen_nic_reg_write(adapter, NETXEN_ROMUSB_ROM_ABYTE_CNT, 3);
> > -	udelay(70);		/* prevent bursting on CRB */
> > +	udelay(100);		/* prevent bursting on CRB */
>
> To prevent PCI write posting issues, you should always do a dummy read
> before
> any delay.

This is a good suggestion. I have the code in place in which i do a dummy read 
of hardware location before the delay. But as of now i have tested this code 
only on some machines. I will like to test it on almost all possible set of 
hardware configurations and put it. With that i am also trying to reduce the 
delay as much as possible.

Till then this patch will make the code work on all hardware platforms 
(including one which require more delay) as well as prevent a softlockup from 
occurring.

Thanks,
Mithlesh Thukral
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