How to activate TLB mapping on m548x ?

[Groleo Marius]

Hi,

I'm trying to activate the TLB mapping in the m548x linux kernel with
the following patch


arch/m68k/coldfire/head.S
====================
/*  ACR0 - System Registers
 *    0xF000 0000   ACR_BA     Base Address
 *    0x000F 0000   ACR_ADMSK  Address Mask
 *    0x0000 8000   ACR_E      Enable the ACR bits
 *    0x0000 2000   ACR_S=1    Dont care accesses are supervisor-only
 *    0x0000 0000   ACR_AMM    Address mode mask
 *    0x0000 0040   ACR_CM=2   Cache-inhibited, precise
 *    0x0000 0008   ACR_SP     Supervisor only
 *    -----------
 *    0xF00F A048
*/
#define ACR0_DEFAULT	#0xF00FA048   /* System Regs */
#define ACR1_DEFAULT	#0x000FA028   /* SDRAM data chache copy-back */
#define ACR2_DEFAULT	#0x00000000   /* Not mapped */
#define ACR3_DEFAULT	#0x000FA028   /* SDRAM code cache copy-back */





just before activating the MMU, a TLB zone is created, using 1MB
pages, the maximum size
Coldfire can support.
/* create 8MB dma memory mirror TLB mapping */
	mmu_map (CONFIG_DMA_BASE + 0*1024*1024), (CONFIG_SDRAM_BASE +
0*1024*1024), 0, 0, \
		MMUTR_SG, MMUDR_SZ1M, MMUDR_DNCP, MMUDR_SP, MMUDR_R, \
		MMUDR_W, 0, MMUDR_LK, %d0

Q: Is it O.K. that the mmu_page is MMUDR_DNCP and the ACR is  data
chache copy-back ?


include/asm-m68k/cf_pgalloc.h
=======================
-struct page *page = alloc_pages(GFP_DMA|__GFP_REPEAT, 0);
+struct page *page = alloc_pages(GFP_KERNEL|__GFP_REPEAT, 0);

Q: Is it O.K. to replace GFP_DMA with GFP_KERNEL ? I think it's not since
the kernel will not allocate new PTE entries in the zone created in head.S.
I tried this instead:
+struct page *page = alloc_pages(GFP_DMA|GFP_KERNEL|__GFP_REPEAT, 0);
but the board hanged, and this made me think of a cache de-synchronization.

Can anyone please help ? Freescale doesn't show any willingness in
offering support.

Many thanks

-- 
Regards!
http://groleo.wordpress.com
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