[U-Boot] Resubmit : [PATCH] Correct ARM Versatile Timer Initialization

[Jean-Christophe PLAGNIOL-VILLARD]

On 08:23 Tue 12 Aug     , Peter Pearse wrote:
>  
> 
> > -----Original Message-----
> > From: Gururaja Hebbar K R [mailto:gururajakr at sanyo.co.in] 
> > Sent: 12 August 2008 03:57
> > To: Jean-Christophe PLAGNIOL-VILLARD
> > Cc: u-boot at lists.denx.de; wd at denx.de; Peter Pearse
> > Subject: RE: Resubmit : [PATCH] Correct ARM Versatile Timer 
> > Initialization
> > 
> >  
> > Hi,
> > 
> > > according to datasheet for the register TimerXControl
> > > 
> > > we are supposed to not modify the bits [31:8] and [4]
> > > 
> > > so we are suppose to read the register and modify only the others 
> > > register.
     s/register/bits/
> > 
> > Does this mean i need to resend the earlier patch. Writing 00 
> > to these bits ( 31:8 & 4) is undefined. 
> 
> Generally, in ARM terminology, one should avoid writing values where writing
> a value or bit is undefined.

Not only in ARM.

> "Undefined" implies, not that there is no result, but that the outcome is
> not defined by the specification.
> Hence it is good practice to read/change/write registers with undefined
> bits, or bits where writing is undefined.

That exaclty what I mean

> This is especially important with bits defined as such in ARM TRMs since
> different ARM customers may implement
> the ARM IP in different ways i.e writing a value to such bits may have
> different results in different implementations
> and or versions of the hardware.

Thanks Peter for the clarification,

Best Regards,
J.