On Thu, 27 Aug 2009 13:11:25 +0200 Detlev Zundel <d...@denx.de> wrote:
> Hi Kim, > > > o LCRR_PDYP, granted dangerous in your case, is obviously a writeable > > bit (not read-only), and documented as such in later documentation. In > > fact, there are no non-writeable bits in LCRR. > > Well, "reserved" != "non-writable" (usually there is a comment that > writing reserved bits produces undefined behaviour) so I agree with > Heiko that as long the documentation that we have access to, designates > bits as reserved, it makes sense to have such a mask. I think we should allow board-configurable writes to the DBYP bit, which is documented as "reserved" on some 83xx, on the 83xx parts that /do/ implement it. So instead of having a mask, perhaps setting absolute values for CONFIG_SYS_LCRR should be replaced with a better scheme that allows board configs to just set LCRR bits by field, such as what the SCCR setting code does. I.e, deprecate CONFIG_SYS_LCRR and replace with individually-specified CONFIG_SYS_LCRR_{CLKDIV,EADC,ECL,BUDCMDC,DBYP} values. This will allow the reserved bits, whether 1 on reset or not, to be preserved across all 83xx (and 85xx for that matter). > > o the user loses visibility into what is going on if they > > decide to drop/add sensitive bits such as LCRR_DBYP in their board's > > CONFIG_SYS_LCRR settings, and there's a mask lurking in the background. > > > > o let's be practical here - in a board port, LCRR settings have to be > > paid attention to, no matter what hidden behaviours or new bits there > > are lying underneath - perhaps the form of 'protection' you seek is in > > the form of a comment in the code? > > So what is it that you propose? That Heiko uses a LCRR in his board > config (over-)writing reserved bits? that's what other boards do (like the 8323erdb), but I do see the problem for the new board porter - they don't see the bit in their documentation, so they omit it. but I presume the above fix will allow Heiko and other new board porters happy? I'll send a patch out this weekend unless someone beats me to it. Kim _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot