tlb0 vs tlb1

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tlb0 vs tlb1

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hv
Contributor II

I saw this in uboot code:

 * As a general rule, TLB0 is used for short-term TLBs, and TLB1 is used for
 * long-term TLBs, so we use TLB0 here.

why is it a general rule that TLB0 is used for short-term and TLB1 is used for long-term?  Does it have to do with IPROT (Invalidate Protect) is only in TLB1?

thanks!

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r8070z
NXP TechSupport
NXP TechSupport

Uboot supports many processors. Let me know name of the uboot code file you refer to.

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381 Views
hv
Contributor II

The comment is in the file start.S in the \arch\popwerpc\mcp85xx directory.

/*

  • Relocate CCSR, if necessary. We relocate CCSR if (obviously) the default

  • location is not where we want it. This typically happens on a 36-bit

  • system, where we want to move CCSR to near the top of 36-bit address space.

*

  • To move CCSR, we create two temporary TLBs, one for the old location, and

  • another for the new location. On CoreNet systems, we also need to create

  • a special, temporary LAW.

*

  • As a general rule, TLB0 is used for short-term TLBs, and TLB1 is used for

  • long-term TLBs, so we use TLB0 here.

*/

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381 Views
r8070z
NXP TechSupport
NXP TechSupport


Have a great day,

Yes this rule due to that
 * IPROT bit is implemented in TLB1 only (prevents invalidations)
and
* TLB0 supports only 4-Kbyte pages, while TLB1) supports the nine (e500v1) or eleven (e500v2) page sizes up to 256-Mbyte (e500v1) and 4-Gbyte (e500v2).

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