Hi, please read the following from MPC85xx UM about the sequence on how to write CCSRBAR: ************************************* When the e500 core is writing to CCSRBAR, it should use the following sequence:
- Read the current value of CCSRBAR using a load word instruction followed by an isync. This forces all accesses to configuration space to complete. - Write the new value to CCSRBAR. - Perform a load of an address that does not access configuration space or the on-chip SRAM, but has an address mapping already in effect (for example, boot ROM). Follow this load with an isync. - Read the contents of CCSRBAR from its new location, followed by another isync instruction. **************************************** The codes between line 287-294 complete the third step above. Haiying ________________________________ From: linuxppc-embedded-bounces+haiying.wang=freescale.com at ozlabs.org [mailto:linuxppc-embedded-bounces+haiying.wang=freescale.com at ozlabs.org] On Behalf Of enorm Sent: Wednesday, August 30, 2006 9:46 AM To: linuxppc-embedded at ozlabs.org Subject: Some problem about code reading Hi, I met some problems when reading sourcecode of u-boot 1.1.4 (for mpc85xx) file /cpu/mpc85xx/start.s line 276 276. #if (CFG_CCSRBAR_DEFAULT != CFG_CCSRBAR) 277. /* Special sequence needed to update CCSRBAR itself */ 278. lis r4, CFG_CCSRBAR_DEFAULT at h 279. ori r4, r4, CFG_CCSRBAR_DEFAULT at l 280. 281. lis r5, CFG_CCSRBAR at h 282. ori r5, r5, CFG_CCSRBAR at l 283. srwi r6,r5,12 284. stw r6, 0(r4) 285. isync 286. 287. lis r5, 0xffff 288. ori r5,r5,0xf000 289. lwz r5, 0(r5) 290. isync 291. 292. lis r3, CFG_CCSRBAR at h 293. lwz r5, CFG_CCSRBAR at l(r3) 294. isync 295. #endif I think it means if we don't use default CCSRBAR, we put the CCSRBAR addr actually used to the proper place in default CCSRBAR, so that it can jump to the addr we want to automatically.(line 276-286). But, I don't know what line 287-294 does. Can some one tell me pls? Thanks for your help. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://ozlabs.org/pipermail/linuxppc-embedded/attachments/20060830/9c392533/attachment.htm