[Edson.Seabra@cyclades.com: Re: BDI and 85xx]

[Edson.Seabra@cyclades.com: Re: BDI and 85xx]

[Marcelo Tosatti]

FYI - how does it look now?


----- Forwarded message from Edson Seabra <Edson.Seabra@cyclades.com> -----

From: Edson Seabra <Edson.Seabra@cyclades.com>
Date: Mon, 14 Nov 2005 12:11:19 -0800
To: "marcelo.tosatti" <Marcelo.Tosatti@cyclades.com>
Subject: Re: BDI and 85xx


Hi, Marcelo.

I re-make the changes following the Dan suggestion.

Can you check if he will accept them this time ?

Thanks,
-Edson.




(See attached file: 8xx_gdb.diff)

Dan Malek <dan@embeddededge.com> wrote on 11/07/2005 09:17:46 AM:

>
> On Nov 7, 2005, at 6:24 AM, Marcelo Tosatti wrote:
>
> > Edson had to patch this in to get BDI to work on 85xx with 2.6.14.
>
> How about we just change MSR_KERNEL and MSR_USER
> in the include file #define instead of all of this run-time code?
> Or, change the code so it preserves DE in general, so we don't
> need a special kernel configuration just for the BDI?
>
> The original reason I did the BDI_SWITCH was due to the
> overhead of tracking user PTE switches in the context switch
> code.  I don't like the way this has been overloaded to mean
> "BDI general operation."  We should be able to attach a BDI2000
> to any kernel configuration and always get kernel debugging
> capability.  The BDI_SWITCH was to enable the extra feature
> (with some overhead) of debugging into user applications,
> it never should have affected any kernel debug operation.
>
> It's unfortunate that Book-E is such a PITA for debuggers,
> but let's please find a better way of using these features.
> Separate kernel configurations to enable hardware
> debugging isn't acceptable.
>
> Thanks.
>
>    -- Dan
>


----- End forwarded message -----

Re: [Edson.Seabra@cyclades.com: Re: BDI and 85xx]

[Marcelo Tosatti]

[-- Attachment #1: Type: text/plain, Size: 159 bytes --]

On Mon, Nov 14, 2005 at 02:45:46PM -0600, Kumar Gala wrote:
> It doesn't look very good since nothing appears to be attached :)

Doh my bad. Attached it is.



[-- Attachment #2: 8xx_gdb.diff --]
[-- Type: text/plain, Size: 705 bytes --]

--- /opt/montavista/pro/devkit/lsp/linux-2.6.14/Makefile	2005-10-27 17:02:08.000000000 -0700
+++ Makefile	2005-11-10 11:32:10.000000000 -0800
@@ -524,7 +524,7 @@
 endif
 
 ifdef CONFIG_DEBUG_INFO
-CFLAGS		+= -g
+CFLAGS		+= -g -ggdb
 endif
 
 include $(srctree)/arch/$(ARCH)/Makefile
--- /opt/montavista/pro/devkit/lsp/linux-2.6.14/include/asm-ppc/reg.h	2005-10-27 17:02:08.000000000 -0700
+++ include/asm-ppc/reg.h	2005-11-10 11:32:10.000000000 -0800
@@ -49,8 +49,12 @@
 #endif
 
 #ifndef MSR_KERNEL
+#ifdef CONFIG_BDI_SWITCH
+#define MSR_KERNEL	(MSR_DE|MSR_ME|MSR_RI|MSR_IR|MSR_DR)
+#else
 #define MSR_KERNEL	(MSR_ME|MSR_RI|MSR_IR|MSR_DR)
 #endif
+#endif
 
 #define MSR_USER	(MSR_KERNEL|MSR_PR|MSR_EE)
 

Re: [Edson.Seabra@cyclades.com: Re: BDI and 85xx]

[Kumar Gala]

It doesn't look very good since nothing appears to be attached :)

- kumar

On Nov 14, 2005, at 9:20 AM, Marcelo Tosatti wrote:

> FYI - how does it look now?
>
>
> ----- Forwarded message from Edson Seabra  
> <Edson.Seabra@cyclades.com> -----
>
> From: Edson Seabra <Edson.Seabra@cyclades.com>
> Date: Mon, 14 Nov 2005 12:11:19 -0800
> To: "marcelo.tosatti" <Marcelo.Tosatti@cyclades.com>
> Subject: Re: BDI and 85xx
>
>
> Hi, Marcelo.
>
> I re-make the changes following the Dan suggestion.
>
> Can you check if he will accept them this time ?
>
> Thanks,
> -Edson.
>
>
>
>
> (See attached file: 8xx_gdb.diff)
>
> Dan Malek <dan@embeddededge.com> wrote on 11/07/2005 09:17:46 AM:
>
>>
>> On Nov 7, 2005, at 6:24 AM, Marcelo Tosatti wrote:
>>
>>> Edson had to patch this in to get BDI to work on 85xx with 2.6.14.
>>
>> How about we just change MSR_KERNEL and MSR_USER
>> in the include file #define instead of all of this run-time code?
>> Or, change the code so it preserves DE in general, so we don't
>> need a special kernel configuration just for the BDI?
>>
>> The original reason I did the BDI_SWITCH was due to the
>> overhead of tracking user PTE switches in the context switch
>> code.  I don't like the way this has been overloaded to mean
>> "BDI general operation."  We should be able to attach a BDI2000
>> to any kernel configuration and always get kernel debugging
>> capability.  The BDI_SWITCH was to enable the extra feature
>> (with some overhead) of debugging into user applications,
>> it never should have affected any kernel debug operation.
>>
>> It's unfortunate that Book-E is such a PITA for debuggers,
>> but let's please find a better way of using these features.
>> Separate kernel configurations to enable hardware
>> debugging isn't acceptable.
>>
>> Thanks.
>>
>>    -- Dan
>>
>
>
> ----- End forwarded message -----
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded

Re: [Edson.Seabra@cyclades.com: Re: BDI and 85xx]

[Dan Malek]

On Nov 14, 2005, at 10:53 AM, Marcelo Tosatti wrote:

> Doh my bad. Attached it is.
>
>
> <8xx_gdb.diff>

Well, this probably works for you but have you
considered how it affects others?

I'm not going to get into the -ggdb flags discussion,
since I know we've had that in the past.  Why is
this needed and should it be done for everyone?

Your update of MSR_KERNEL will work for you,
but won't work on anything that isn't a Book E processor.
You can't make this a generic update to all processors.
It will fail on everything that really wants to use the
BDI_SWITCH configuration option as it was intended.
The DE in Book E conflicts with BE in traditional PPC.

This also doesn't do anything to address my real concern,
we shouldn't have to create a special kernel configuration
just to attach a debugger .........

Thanks.


	-- Dan

Re: [Edson.Seabra@cyclades.com: Re: BDI and 85xx]

[Kumar Gala]

On Nov 14, 2005, at 4:43 PM, Dan Malek wrote:

>
> On Nov 14, 2005, at 10:53 AM, Marcelo Tosatti wrote:
>
>> Doh my bad. Attached it is.
>>
>>
>> <8xx_gdb.diff>
>
> Well, this probably works for you but have you
> considered how it affects others?
>
> I'm not going to get into the -ggdb flags discussion,
> since I know we've had that in the past.  Why is
> this needed and should it be done for everyone?
>
> Your update of MSR_KERNEL will work for you,
> but won't work on anything that isn't a Book E processor.
> You can't make this a generic update to all processors.
> It will fail on everything that really wants to use the
> BDI_SWITCH configuration option as it was intended.
> The DE in Book E conflicts with BE in traditional PPC.

We should but this in asm-ppc/reg_booke.h since book-e has its own  
MSR_* defines.

> This also doesn't do anything to address my real concern,
> we shouldn't have to create a special kernel configuration
> just to attach a debugger .........

I'm not 100% sure this is even possible on some of the book-e variants.

- kumar

Re: [Edson.Seabra@cyclades.com: Re: BDI and 85xx]

[Dan Malek]

On Nov 14, 2005, at 5:50 PM, Kumar Gala wrote:

> I'm not 100% sure this is even possible on some of the book-e variants.

I suspect we could if we didn't just keep whacking
the MSR with some constant value :-) What
happens if we just leave DE set all of the time?
I know as part of ptrace, etc. it can get manipulated,
but if we are debugging through COP we shouldn't
get to these software functions.

	-- Dan