[Linux-Xtensa] Modifying the proto for operator overloading

Marc Gauthier marc at tensilica.com
Fri Feb 1 05:59:11 PST 2013


If the proto is only used for register save/restore sequences used by the kernel, it is possible to edit the overlay tarball (that is used to build tools and kernel for your core configuration) by hand.  However, it's generally much easier to regenerate the core, which takes an hour or so.  Your mention of operator overloading sounds like you're using this with the Tensilica compiler (XCC); such use is not so easy to update without regenerating the core (or maybe using tc).  Sounds like you no longer have access?  Did you ask your Tensilica support contact?


From: linux-xtensa-bounces at linux-xtensa.org [mailto:linux-xtensa-bounces at linux-xtensa.org] On Behalf Of pradeep
Sent: Friday, February 01, 2013 01:20
To: Pete Delaney; Chris Zankel; Pete Delaney
Cc: linux-xtensa at linux-xtensa.org; Mahavir Prasad; Max Filippov
Subject: [Linux-Xtensa] Modifying the proto for operator overloading

Hello all,
          I am stuck in a tricky situation. I have finalized my TIE and have generated my build. In the TIE I have used same operation to define 3-4 proto, and used them in operator overloading. One of this proto has some bug ( Attn: the instruction (TIE operation) it uses,  is perfectly fine). Now I cant change my TIE file. So is it posssible to change the defination of this proto without needing to regnerate the Core. I want to change the proto to call some other operation than it presently calling.


-- Original Message --
From: Pete Delaney <piet.delaney at gmail.com>
To: Chris Zankel <chris at zankel.net>,
Pete Delaney <piet.delaney at gmail.com>
Cc: linux-xtensa at linux-xtensa.org, Mahavir Prasad <er.mahavir at gmail.com>,
Max Filippov <jcmvbkbc at gmail.com>
Date: Tue, 29 Jan 2013 20:05:31 -0800
Subject: Re: [Linux-Xtensa] Re: [PATCH 0/3] xtensa: add MMUv3 and medium-level
interrupts support

On 01/14/2013 07:57 AM, Chris Zankel wrote:
> Sorry, missed them. Added to for_next.
> Thanks,
> -Chris
> On 1/12/13 10:04 PM, Max Filippov wrote:
>> On Sun, Jan 13, 2013 at 9:29 AM, Chris Zankel <chris at zankel.net> wrote:
>>> Hi Max,
>>> I have applied your patches except for the MMU v3 patch. It feels that
>>> it needs a bit more clean-up, but I need to go through it more
>>> thoroughly to be sure. For example, it's about MMU, but the description
>>> only talks about GDB. The comments in general feel overwhelming.
>>> Although, they maybe necessarily need to be. I'll get back to you on
>>> this one.
The folks in India found it very helpful while bringing up their V3 MMU
to be able to single step through the initial TLB brain surgery and for
DDD+gdb to correctly display the code, even when switching from the
initial virtual == physical, through to the 0x4000,000 mapping, and then
to the final 0xd000,0000 mapping.

Most CPU don't even support doing the TLB re-mapping in the kernel.
This TLB remapping sure makes it a lot easier when debugging early
startup with JTAG.

Try single stepping the early MMU initialisation with DDD+GDB and see
for yourself if it's not worth it. This is very very early
initialisation, having
a clear definition of what the TLB should look like is extremely valuable,
at least from my experience when I did it and with Mahavir last year when
we had a bug during this early startup phase. Marc recognised the root cause
when the TLB was out of sync a few stack frames later when initialising the
platform code. This early environment is nasty when things go haywire.
When bringing up a chip all kinds of hardware mistakes could cause bizarre
problems that are difficult to diagnose. Having a guiding hand during the
first 60 instructions of life can be god send.


>> Thank you, Chris.
>> BTW, there are two more fixes in the xtensa-fixes-for-upstream branch
>> that were posted a while ago, but somehow missed your for_next branch:
>> c6e407d xtensa: add finit_module syscall
>> 0fbadfb xtensa: avoid mmap cache aliasing
>> I have rebased them on top of the for_next, could you please take them
>> as well?
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> linux-xtensa at linux-xtensa.org
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