Reading an entire cacheline

Hi,

Is there any way to read an entire cacheline from the MIPS5Kf? Four sequential cache instructions do similarly, but sometimes the tags from a same cacheline differ. How can I read a consistent cacheline safely?

Thanks.

Hi all,

Was my question too brief? I'm using MIPS5Kf core included in a Broadcom implemented processor and it has a 32kB d-cache and a same sized i-cache. Cache configuration is 2-way, 32-byte cacheline for both d- and i-cache without L2 cache. Of course, MIPS-port Linux as the kernel for it. And, a onboard block device has problem in its operation. I don't think it's a kernel problem. So I wanna inspect the contents of cache RAMs at the device driver's context. I've added some lines of codes look like follow:

	__asm__ __volatile__(
		".set	noreorder\n\t"
		".set	mips3\n\t"
		"cache	5, 0x00(%3)\n\t"	// load d-cache tag
		".set	mips0\n\t"		// by index
		".set	mips32\n\t"
		"mfc0	%0, $28, 0\n\t"
		"mfc0	%1, $28, 1\n\t"
		"mfc0	%2, $29, 1\n\t"
		.set	mips0\n\t"
		.set	reorder"
		: "=r" (tag), "=r" (data_lo), "=r" (data_hi)
		: "r" (0x80000000 | (way << 14) | (index << 5) | (word <<
3))
	);

This is executed for every index, every way, and every word. The thing aches my head is the tags from a single cacheline differs. (very often for d-cache) So I modified the code to reread the cacheline from the first word when the tag was modified before reading all four words. Then the code never return. I couldn't find any related information from manual.

Please give me a hint for reading whole cacheline safely.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Kim, Jong-Sung
Sent: Tuesday, April 18, 2006 9:37 AM
To: [email protected]
Subject: Reading an entire cacheline

Hi,

Is there any way to read an entire cacheline from the MIPS5Kf? Four sequential cache instructions do similarly, but sometimes the tags from a same cacheline differ. How can I read a consistent cacheline safely?

Thanks.

Yes, your question was too brief the first time around - I couldn't tell what you were really asking. I'm still not 100% sure of what
you're doing, though. I don't want to sound insulting, but you're
disabling interrupts during this operation, right? And if you're copying the values into variables in memory, you're doing nothing but non-cached references, right? When you see the tags changing on you, which bits are changing, and what are they defined to mean?

Regards,

Kevin K.

----- Original Message -----
From: "Kim, Jong-Sung" <[email protected]>
To: <[email protected]>
Sent: Monday, April 24, 2006 9:23 AM
Subject: RE: Reading an entire cacheline