netdev - Re: [PATCH] ethernet: e1000e: define lat

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Date:	Wed, 08 Apr 2015 11:13:02 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	"'yanjiang.jin@...driver.com'" <yanjiang.jin@...driver.com>,
	"bruce.w.allan@...el.com" <bruce.w.allan@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jinyanjiang@...il.com" <jinyanjiang@...il.com>,
	intel-wired-lan <intel-wired-lan@...ts.osuosl.org>
Subject: Re: [PATCH] ethernet: e1000e: define lat_ns as u64 instead of s64

On Wed, 2015-04-08 at 09:40 +0000, David Laight wrote:
> From: yanjiang.jin@...driver.com
> > Sent: 03 April 2015 10:18
> > From: Yanjiang Jin <yanjiang.jin@...driver.com>
> > 
> > do_div() expects the type of "n" to be uint64_t, define "lat_ns" as u64 to
> > avoid the below warning, also update its correlative operations and data.
> > 
> > In file included from ./arch/powerpc/include/asm/div64.h:1:0,
> >                  from include/linux/kernel.h:124,
> >                  from include/linux/list.h:8,
> >                  from include/linux/timer.h:4,
> >                  from drivers/net/ethernet/intel/e1000e/e1000.h:29,
> >                  from drivers/net/ethernet/intel/e1000e/ich8lan.c:59:
> > drivers/net/ethernet/intel/e1000e/ich8lan.c: In function 'e1000_platform_pm_pch_lpt':
> > include/asm-generic/div64.h:43:28: warning: comparison of distinct pointer types lacks a cast [enabled
> > by default]
> >   (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
> >                             ^
> > drivers/net/ethernet/intel/e1000e/ich8lan.c:1016:4: note: in expansion of macro 'do_div'
> >     do_div(lat_ns, speed);
> > 
> > Signed-off-by: Yanjiang Jin <yanjiang.jin@...driver.com>
> > ---
> >  drivers/net/ethernet/intel/e1000e/ich8lan.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
> > index 48b74a5..baab58b 100644
> > --- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
> > +++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
> > @@ -982,8 +982,8 @@ static s32 e1000_platform_pm_pch_lpt(struct e1000_hw *hw, bool link)
> >  		u16 speed, duplex, scale = 0;
> >  		u16 max_snoop, max_nosnoop;
> >  		u16 max_ltr_enc;	/* max LTR latency encoded */
> > -		s64 lat_ns;	/* latency (ns) */
> > -		s64 value;
> > +		u64 lat_ns;	/* latency (ns) */
> > +		u64 value;
> >  		u32 rxa;
> > 
> >  		if (!hw->adapter->max_frame_size) {
> > @@ -1008,8 +1008,8 @@ static s32 e1000_platform_pm_pch_lpt(struct e1000_hw *hw, bool link)
> >  		 * 2^25*(2^10-1) ns.  The scale is encoded as 0=2^0ns,
> >  		 * 1=2^5ns, 2=2^10ns,...5=2^25ns.
> >  		 */
> > -		lat_ns = ((s64)rxa * 1024 -
> > -			  (2 * (s64)hw->adapter->max_frame_size)) * 8 * 1000;
> > +		lat_ns = ((u64)rxa * 1024 -
> > +			  (2 * (u64)hw->adapter->max_frame_size)) * 8 * 1000;
> >  		if (lat_ns < 0)
> >  			lat_ns = 0;
> 
> The above change cannot be correct.
> You should be getting another error for testing an unsigned value be less than 0.
> 
> So I presume this wasn't even tested.
> 

I found the same issue and I am putting together another patch to
resolve the issue that Yanjiang saw.

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