14 Aug
2014
14 Aug
'14
12:54 a.m.
On Wed, 2014-08-13 at 17:44 -0400, Bill Pringlemeir wrote:
Regarding "can't know in advance", I think that some of the register values maybe set by the boot rom. This might make more sense for Linux than U-Boot. However, after the initial configuration, many do need the 'read/modify/write' as there are many bit fields with different functionality.
If the register is only modified by software, and not asynchronously by hardware, then you could read the value once when the driver starts, and cache its value to avoid a reportedly expensive I/O access every time you need to modify it.
-Scott