Friends,
I'm reading section 3.3.4 (RAM Read Pointer Register) of the "CoreSight Trace Memory Controller Technical Reference Manual", revision r0p1 and I'm puzzled.
The second paragraph of the "Purpose" section reads as follow:
"The value written to this register must be a byte-address aligned to the width of the trace memory databus and to a frame boundary. For example, for 64-bit wide trace memory and 128-bit wide trace memory, the four LSBs must be 0s. For 256-bit wide trace memory, the five LSBs must be 0s..."
So for 64 bit wide memory RRP can be set to values like 0, 8, 16, 24... for 128 bit 0, 16, 32, 48... and for 256 bit 0, 32, 64...
What is perplexing is the statement about the LSBs. Things work for 256 bit and 128 bit with 5 and 4 LSBs respectively but for 64 bit, it should be 3 and not 4 as mentioned.
Am I missing something here? Can someone double check me?
Thanks, Mathieu
Hi Mathieu,
Don't forget the "and to a frame boundary" portion of the definition. A formatted trace frame is 16 bytes in size - hence 128 bits, therefore the alignment of 64 and 128 bit address ranges must be the same (and 32 bit for that matter). Only when you get memory widths that are actually larger than a trace frame does the memory width alignment kick in as the dominating factor.
Regards
Mike
-----Original Message----- From: CoreSight [mailto:coresight-bounces@lists.linaro.org] On Behalf Of Mathieu Poirier Sent: 24 November 2015 21:10 To: coresight@lists.linaro.org Subject: TMC RAM Read Pointer
Friends,
I'm reading section 3.3.4 (RAM Read Pointer Register) of the "CoreSight Trace Memory Controller Technical Reference Manual", revision r0p1 and I'm puzzled.
The second paragraph of the "Purpose" section reads as follow:
"The value written to this register must be a byte-address aligned to the width of the trace memory databus and to a frame boundary. For example, for 64-bit wide trace memory and 128-bit wide trace memory, the four LSBs must be 0s. For 256-bit wide trace memory, the five LSBs must be 0s..."
So for 64 bit wide memory RRP can be set to values like 0, 8, 16, 24... for 128 bit 0, 16, 32, 48... and for 256 bit 0, 32, 64...
What is perplexing is the statement about the LSBs. Things work for 256 bit and 128 bit with 5 and 4 LSBs respectively but for 64 bit, it should be 3 and not 4 as mentioned.
Am I missing something here? Can someone double check me?
Thanks, Mathieu _______________________________________________ CoreSight mailing list CoreSight@lists.linaro.org https://lists.linaro.org/mailman/listinfo/coresight
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On 24 November 2015 at 17:13, Mike Leach Mike.Leach@arm.com wrote:
Hi Mathieu,
Don't forget the "and to a frame boundary" portion of the definition. A formatted trace frame is 16 bytes in size - hence 128 bits, therefore the alignment of 64 and 128 bit address ranges must be the same (and 32 bit for that matter). Only when you get memory widths that are actually larger than a trace frame does the memory width alignment kick in as the dominating factor.
Mike,
Many thanks for the clarification - I would have never guessed. Your explanation will be added as a comment (almost verbatim) in the code.
Regards
Mike
-----Original Message----- From: CoreSight [mailto:coresight-bounces@lists.linaro.org] On Behalf Of Mathieu Poirier Sent: 24 November 2015 21:10 To: coresight@lists.linaro.org Subject: TMC RAM Read Pointer
Friends,
I'm reading section 3.3.4 (RAM Read Pointer Register) of the "CoreSight Trace Memory Controller Technical Reference Manual", revision r0p1 and I'm puzzled.
The second paragraph of the "Purpose" section reads as follow:
"The value written to this register must be a byte-address aligned to the width of the trace memory databus and to a frame boundary. For example, for 64-bit wide trace memory and 128-bit wide trace memory, the four LSBs must be 0s. For 256-bit wide trace memory, the five LSBs must be 0s..."
So for 64 bit wide memory RRP can be set to values like 0, 8, 16, 24... for 128 bit 0, 16, 32, 48... and for 256 bit 0, 32, 64...
What is perplexing is the statement about the LSBs. Things work for 256 bit and 128 bit with 5 and 4 LSBs respectively but for 64 bit, it should be 3 and not 4 as mentioned.
Am I missing something here? Can someone double check me?
Thanks, Mathieu _______________________________________________ CoreSight mailing list CoreSight@lists.linaro.org https://lists.linaro.org/mailman/listinfo/coresight
-- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
-
Mathieu Poirier -
Mike Leach