From: Jiri Gaisler <jiri@xxxxxxxxxx> Date: Wed, 16 May 2012 14:55:48 +0200 > > > Sam Ravnborg wrote: > >> Konrad / Daniel - any inputs on why LEON uses a different ASI? >> As we uses this in head_32.S this is really annoying... > > It is not difficult to change the MMU reg ASI from 0x19 to 0x4 > (as defined in the SRMMU spec). However, all available LEON2/3/4 > chips in production uses 0x19 due to a decision take about 10 > years ago. ASI 4 was used for uncached access in the original > MMU-less LEON2, hence the choice to use 0x19. In current LEON3/4 > cores, ASI 4 is no longer used, so 0x19 could easily be replaced > with 4. But removing the use of ASI 0x19 in the kernel will make > it incompatible with all present chips. I will change the LEON3/4 > IP's to double map the MMU ASI to both 4 and 0x19, but then we have > to wait an other 10 years until the present chips are out of use > before we can remove 0x19 from the kernel ... This is not what we're asking you to do. We're asking you to rearrange the code so that we can set ASI_M_MMUREGS to it's proper SRMMU value, and then you change all the LEON code to take different paths and use Leon specific code to program the MMU. In that way we can have one kernel image that boots properly on all cpu types, rather than the current broken situation where a Leon enabled build makes the kernel unbootable on real SRMMU chips. -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
