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| author | York Sun <yorksun@freescale.com> | 2012-10-08 07:44:30 +0000 |
|---|---|---|
| committer | Andy Fleming <afleming@freescale.com> | 2012-10-22 14:31:32 -0500 |
| commit | ffd06e0231ac3fd0c5810f39f6e23527948df1c7 (patch) | |
| tree | 7d648c2c312b9cc7a75c0350101aacc67afca399 /doc | |
| parent | 3f0997b3255c1498ac92453aa3a7a1cc95914dfd (diff) | |
| download | u-boot-imx-ffd06e0231ac3fd0c5810f39f6e23527948df1c7.zip u-boot-imx-ffd06e0231ac3fd0c5810f39f6e23527948df1c7.tar.gz u-boot-imx-ffd06e0231ac3fd0c5810f39f6e23527948df1c7.tar.bz2 | |
powerpc/mpc85xx: Rewrite spin table to comply with ePAPR v1.1
Move spin table to cached memory to comply with ePAPR v1.1.
Load R3 with 64-bit value if CONFIG_SYS_PPC64 is defined.
'M' bit is set for DDR TLB to maintain cache coherence.
See details in doc/README.mpc85xx-spin-table.
Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/README.mpc85xx-spin-table | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/doc/README.mpc85xx-spin-table b/doc/README.mpc85xx-spin-table new file mode 100644 index 0000000..8da768a --- /dev/null +++ b/doc/README.mpc85xx-spin-table @@ -0,0 +1,26 @@ +Spin table in cache +===================================== +As specified by ePAPR v1.1, the spin table needs to be in cached memory. After +DDR is initialized and U-boot relocates itself into DDR, the spin table is +accessible for core 0. It is part of release.S, within 4KB range after +__secondary_start_page. For other cores to use the spin table, the booting +process is described below: + +Core 0 sets up the reset page on the top 4K of memory (or 4GB if total memory +is more than 4GB), and creates a TLB to map it to 0xffff_f000, regardless of +the physical address of this page, with WIMGE=0b01010. Core 0 also enables boot +page translation for secondary cores to use this page of memory. Then 4KB +memory is copied from __secondary_start_page to the boot page, after flusing +cache because this page is mapped as normal DDR. Before copying the reset page, +core 0 puts the physical address of the spin table (which is in release.S and +relocated to the top of mapped memory) into a variable __spin_table_addr so +that secondary cores can see it. + +When secondary cores boot up from 0xffff_f000 page, they only have one default +TLB. While booting, they set up another TLB in AS=1 space and jump into +the new space. The new TLB covers the physical address of the spin table page, +with WIMGE =0b00100. Now secondary cores can keep polling the spin table +without stress DDR bus because both the code and the spin table is in cache. + +For the above to work, DDR has to set the 'M' bit of WIMGE, in order to keep +cache coherence. |