Re: [PATCH] libata: warn if speed limited due to 40-wire cable (v2)

[Stephen Clark]

Bill Davidsen wrote:

> Stephen Clark wrote:
>  
>
> > Bill Davidsen wrote:
> >
> >    
> >
> > > Alan Cox wrote:
> > >
> > >
> > >      
> > >
> > > > > it seems broken to manipulate xfer_mask after returning from the 
> > > > > driver's ->mode_filter hook.
> > > > >
> > > > > this patch is more than just a speed-limited warning printk, afaics
> > > > >    
> > > > >          
> > > > I actually suggested that order because the only way the printk can be
> > > > done correctly is for it to be the very last test made. Since the mode
> > > > filter is not told what mode will be used but just subtracts modes that
> > > > are not allowed this should be safe.
> > > >  
> > > >        
> > > Far better to have a drive which works slowly than one which works 
> > > unreliably.
> > >
> > >
> > >
> > >      
> > That would be true if the 40 wire detection was 100% accurate!
> >    
> The statement is completely correct, even though the detection may not 
> be. ;-)
>
> With the current set(s) of patches to do better detection, cable 
> evaluation should be better. But even if not, a slow system is more 
> useful than one which doesn't work, crashes because of swap i/o errors, etc.
>
>  
I have had problems with cable detection on my previous laptop and my 
current laptop. It almost made
my systems unusable. On my current laptop I was getting a thruput of a 
little over 1 mbps instead
of the 44 mbps I get with udma set to the correct value. It took hours 
to upgrade my laptop from
fc5 to fc6 because of this mis detection.

--

"They that give up essential liberty to obtain temporary safety, 
deserve neither liberty nor safety."  (Ben Franklin)

"The course of history shows that as a government grows, liberty 
decreases."  (Thomas Jefferson)



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