On 08:23 Tue 12 Aug , Peter Pearse wrote:
-----Original Message----- From: Gururaja Hebbar K R [mailto:gururajakr@sanyo.co.in] Sent: 12 August 2008 03:57 To: Jean-Christophe PLAGNIOL-VILLARD Cc: u-boot@lists.denx.de; wd@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.