Re: [PATCH] MIPS: Calculate proper ebase value for 64-bit kernels

[David Daney <ddaney@caviumnetworks.com>]

On 04/26/2010 06:25 PM, post@pfrst.de wrote:
>
>
> Hi David,
>
> please excuse me, i just couldn't resist to comment on this :-)
>
> Some time ago we needed to handle multiple (virtual) address-spaces
> (in TO_CAC/TO_UNCAC as well as in virt_to_phys and the like) for
> SGI's Indigo2/R10k and Octane (neither could run a 32bit kernel).
> So in addrspace.h we provided
> 	#ifdef CONFIG_64BIT
> 	static inline unsigned long kernel_physaddr(unsigned long kva)
> 	{
> 		if((kva&0xffffffff80000000UL)==0xffffffff80000000UL)
> 			return CPHYSADDR(kva);
> 		return XPHYSADDR(kva);
> 	}
> 	#else
> 	#define kernel_physaddr CPHYSADDR
> 	#endif
> while mach-ipXX/spaces.h defined
> 	#define TO_PHYS(x)	(             kernel_physaddr(x))
> 	#define TO_CAC(x)	(CAC_BASE   | kernel_physaddr(x))
> 	#define TO_UNCAC(x)	(UNCAC_BASE | kernel_physaddr(x))
> which did the job.
> But at that time these defines didn't meet much acceptance for general
> use in 64bit kernels.  Now, to my amusement, some modern processor
> (and/or system) seems to urge this kind of address-handling again  ;-)
>
>

FWIW, that seems cleaner than what I did (actually I didn't try my 
code).  That should be the default definition for 64-bit kernels I think.

David Daney

> Good luck!
>
>
>
> On Mon, 26 Apr 2010, David Daney wrote:
>
>> Date: Mon, 26 Apr 2010 10:19:04 -0700
>> From: David Daney<ddaney@caviumnetworks.com>
>> To: wuzhangjin@gmail.com
>> Cc: Ralf Baechle<ralf@linux-mips.org>,
>>       Thomas Bogendoerfer<tsbogend@alpha.franken.de>,
>>       linux-mips@linux-mips.org
>> Subject: Re: [PATCH] MIPS: Calculate proper ebase value for 64-bit kernels
>>
>> ...
>> I don't think so.  We should fix TO_UNCAC() so that it works with CKSEG0
>> addresses.  It should be at physical address 0.  So
>> TO_UNCAC(0xffffffff80000000), should yield 0x9000000000000000
>>
>>
>> #define TO_UNCAC(x) ({ \
>> 	u64 a = (u64)(x);     \
>> 	if (a&  0xffffffffc000000 == 0xffffffff80000000) \
>> 		a = UNCAC_BASE | (a&  0x30000000); \
>> 	else \
>> 		a = UNCAC_BASE | (a&  TO_PHYS_MASK) \
>> 	a; \
>> })
>>
>> David Daney
>>
>> ...
>