Help needed to understand code

[Shubhangi Jadhav]

Hi,

I'm a LinuxBIOS newbie. I have downloaded the source code for the same and
was trying to understand it. Looks too complicated to me.
    I'd started with the code for Intel440gx mainboard, but failed to
understand how the northbridge and southbridge intialization routines are
invoked.
    Can someone tell me how to go about understanding the code?

Thanks,
Shubhangi

[steven james]

Greetings,

Probably the first thing to understand is the overall flow of control.

On powerup, the reset vector at f000:fff0 jumps to the start of the
assembly code. The assembly code consists of a series of modular units
that the config files paste together using include directives. It just
starts at the beginning, and new pieces are tacked on as encountered in
the config files. The config files are invoked by directives like
northbridge and southbridge. The master config file is in the mainboard
directory and is invoked by the user's config file.  Most mainboard
directory have example user configs.

The c code is linked together seperatly and then compressed. The last part
of the asm code decompresses it into RAM and calls hardwaremain
(found in src/arch/<arch>/lib/hardwaremain.c currently, <arch> can be
alpha, i386 or ppc). The remainder of the C code is all invoked from
there.

G'day,
sjames

On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> Hi,
>
> I'm a LinuxBIOS newbie. I have downloaded the source code for the same and
> was trying to understand it. Looks too complicated to me.
>    I'd started with the code for Intel440gx mainboard, but failed to
> understand how the northbridge and southbridge intialization routines are
> invoked.
>    Can someone tell me how to go about understanding the code?
>
> Thanks,
> Shubhangi
>
> Linuxbios mailing list
> [e-mail]
> http://www.clustermatic.org/mailman/listinfo/linuxbios

[Shubhangi Jadhav]

Hi,

However according to the LinuxBIOS readme the assembly code calls
intel_main in freebios/chip/intel/intel_main.c which in turn calls
linuxbios_main in linuxbios/inflate/main.c. So is intel_main called first or
hardwaremain. Am I missing something
    Please elaborate more on the flow.

Thanks,
Shubhangi

-----Original Message-----
From: steven james [mailto:[e-mail]]
Sent: Friday, March 07, 2003 6:29 PM
To: Shubhangi Jadhav
Cc: [e-mail]
Subject: Re: Help needed to understand code

Greetings,

Probably the first thing to understand is the overall flow of control.

On powerup, the reset vector at f000:fff0 jumps to the start of the
assembly code. The assembly code consists of a series of modular units
that the config files paste together using include directives. It just
starts at the beginning, and new pieces are tacked on as encountered in
the config files. The config files are invoked by directives like
northbridge and southbridge. The master config file is in the mainboard
directory and is invoked by the user's config file.  Most mainboard
directory have example user configs.

The c code is linked together seperatly and then compressed. The last part
of the asm code decompresses it into RAM and calls hardwaremain
(found in src/arch/<arch>/lib/hardwaremain.c currently, <arch> can be
alpha, i386 or ppc). The remainder of the C code is all invoked from
there.

G'day,
sjames

On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> Hi,
>
> I'm a LinuxBIOS newbie. I have downloaded the source code for the same

and
> was trying to understand it. Looks too complicated to me.
>    I'd started with the code for Intel440gx mainboard, but failed to
> understand how the northbridge and southbridge intialization routines are
> invoked.
>    Can someone tell me how to go about understanding the code?
>
> Thanks,
> Shubhangi
>
> Linuxbios mailing list
> [e-mail]
> http://www.clustermatic.org/mailman/listinfo/linuxbios

[steven james]

Greetings,

By chance, are you looking at a snapshot tarball? If so, that's very
old. The best bet is to check out the CVS tree from sourceforge. These
days, intel_main is gone and there's nothing in the chip directory.

G'day,
sjames

On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> Hi,
>
> However according to the LinuxBIOS readme the assembly code calls
> intel_main in freebios/chip/intel/intel_main.c which in turn calls
> linuxbios_main in linuxbios/inflate/main.c. So is intel_main called first or
> hardwaremain. Am I missing something
>    Please elaborate more on the flow.
>
> Thanks,
> Shubhangi
>
> -----Original Message-----
> From: steven james [mailto:[e-mail]]
> Sent: Friday, March 07, 2003 6:29 PM
> To: Shubhangi Jadhav
> Cc: [e-mail]
> Subject: Re: Help needed to understand code
>
> Greetings,
>
> Probably the first thing to understand is the overall flow of control.
>
> On powerup, the reset vector at f000:fff0 jumps to the start of the
> assembly code. The assembly code consists of a series of modular units
> that the config files paste together using include directives. It just
> starts at the beginning, and new pieces are tacked on as encountered in
> the config files. The config files are invoked by directives like
> northbridge and southbridge. The master config file is in the mainboard
> directory and is invoked by the user's config file.  Most mainboard
> directory have example user configs.
>
> The c code is linked together seperatly and then compressed. The last part
> of the asm code decompresses it into RAM and calls hardwaremain
> (found in src/arch/<arch>/lib/hardwaremain.c currently, <arch> can be
> alpha, i386 or ppc). The remainder of the C code is all invoked from
> there.
>
> G'day,
> sjames
>
> On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> > Hi,
> >
> > I'm a LinuxBIOS newbie. I have downloaded the source code for the same
>
> and
> > was trying to understand it. Looks too complicated to me.
> >    I'd started with the code for Intel440gx mainboard, but failed to
> > understand how the northbridge and southbridge intialization routines are
> > invoked.
> >    Can someone tell me how to go about understanding the code?
> >
> > Thanks,
> > Shubhangi
> >
> > Linuxbios mailing list
> > [e-mail]
> > http://www.clustermatic.org/mailman/listinfo/linuxbios
>
> Linuxbios mailing list
> [e-mail]
> http://www.clustermatic.org/mailman/listinfo/linuxbios

[Shubhangi Jadhav]

Hi,

Yes I downloaded the snapshot from the website, since it mentions that it's
the daily snapshot of the source. Can you please update the snapshot on the
website.

Thanks,
Shubhangi

-----Original Message-----
From: steven james [mailto:[e-mail]]
Sent: Friday, March 07, 2003 8:00 PM
To: Shubhangi Jadhav
Cc: [e-mail]
Subject: RE: Help needed to understand code

Greetings,

By chance, are you looking at a snapshot tarball? If so, that's very
old. The best bet is to check out the CVS tree from sourceforge. These
days, intel_main is gone and there's nothing in the chip directory.

G'day,
sjames

On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> Hi,
>
> However according to the LinuxBIOS readme the assembly code calls
> intel_main in freebios/chip/intel/intel_main.c which in turn calls
> linuxbios_main in linuxbios/inflate/main.c. So is intel_main called first

or
> hardwaremain. Am I missing something
>    Please elaborate more on the flow.
>
> Thanks,
> Shubhangi
>
> -----Original Message-----
> From: steven james [mailto:[e-mail]]
> Sent: Friday, March 07, 2003 6:29 PM
> To: Shubhangi Jadhav
> Cc: [e-mail]
> Subject: Re: Help needed to understand code
>
> Greetings,
>
> Probably the first thing to understand is the overall flow of control.
>
> On powerup, the reset vector at f000:fff0 jumps to the start of the
> assembly code. The assembly code consists of a series of modular units
> that the config files paste together using include directives. It just
> starts at the beginning, and new pieces are tacked on as encountered in
> the config files. The config files are invoked by directives like
> northbridge and southbridge. The master config file is in the mainboard
> directory and is invoked by the user's config file.  Most mainboard
> directory have example user configs.
>
> The c code is linked together seperatly and then compressed. The last part
> of the asm code decompresses it into RAM and calls hardwaremain
> (found in src/arch/<arch>/lib/hardwaremain.c currently, <arch> can be
> alpha, i386 or ppc). The remainder of the C code is all invoked from
> there.
>
> G'day,
> sjames
>
> On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> > Hi,
> >
> > I'm a LinuxBIOS newbie. I have downloaded the source code for the same
>
> and
> > was trying to understand it. Looks too complicated to me.
> >    I'd started with the code for Intel440gx mainboard, but failed to
> > understand how the northbridge and southbridge intialization routines

are
> > invoked.
> >    Can someone tell me how to go about understanding the code?
> >
> > Thanks,
> > Shubhangi
> >
> > Linuxbios mailing list
> > [e-mail]
> > http://www.clustermatic.org/mailman/listinfo/linuxbios
>
> Linuxbios mailing list
> [e-mail]
> http://www.clustermatic.org/mailman/listinfo/linuxbios

[Shubhangi Jadhav]

Hi,

Could anyone tell me what are the .inc files found in the LinuxBIOS source?
    Are these generated from the C code (for the sdram code I could see an
association between the .c and corresponding .inc) and how ?

Thanks,
Shubhangi

-----Original Message-----
From: steven james [mailto:[e-mail]]
Sent: Friday, March 07, 2003 8:00 PM
To: Shubhangi Jadhav
Cc: [e-mail]
Subject: RE: Help needed to understand code

Greetings,

By chance, are you looking at a snapshot tarball? If so, that's very
old. The best bet is to check out the CVS tree from sourceforge. These
days, intel_main is gone and there's nothing in the chip directory.

G'day,
sjames

On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> Hi,
>
> However according to the LinuxBIOS readme the assembly code calls
> intel_main in freebios/chip/intel/intel_main.c which in turn calls
> linuxbios_main in linuxbios/inflate/main.c. So is intel_main called first

or
> hardwaremain. Am I missing something
>    Please elaborate more on the flow.
>
> Thanks,
> Shubhangi
>
> -----Original Message-----
> From: steven james [mailto:[e-mail]]
> Sent: Friday, March 07, 2003 6:29 PM
> To: Shubhangi Jadhav
> Cc: [e-mail]
> Subject: Re: Help needed to understand code
>
> Greetings,
>
> Probably the first thing to understand is the overall flow of control.
>
> On powerup, the reset vector at f000:fff0 jumps to the start of the
> assembly code. The assembly code consists of a series of modular units
> that the config files paste together using include directives. It just
> starts at the beginning, and new pieces are tacked on as encountered in
> the config files. The config files are invoked by directives like
> northbridge and southbridge. The master config file is in the mainboard
> directory and is invoked by the user's config file.  Most mainboard
> directory have example user configs.
>
> The c code is linked together seperatly and then compressed. The last part
> of the asm code decompresses it into RAM and calls hardwaremain
> (found in src/arch/<arch>/lib/hardwaremain.c currently, <arch> can be
> alpha, i386 or ppc). The remainder of the C code is all invoked from
> there.
>
> G'day,
> sjames
>
> On Fri, 7 Mar 2003, Shubhangi Jadhav wrote:
> > Hi,
> >
> > I'm a LinuxBIOS newbie. I have downloaded the source code for the same
>
> and
> > was trying to understand it. Looks too complicated to me.
> >    I'd started with the code for Intel440gx mainboard, but failed to
> > understand how the northbridge and southbridge intialization routines

are
> > invoked.
> >    Can someone tell me how to go about understanding the code?
> >
> > Thanks,
> > Shubhangi
> >
> > Linuxbios mailing list
> > [e-mail]
> > http://www.clustermatic.org/mailman/listinfo/linuxbios
>
> Linuxbios mailing list
> [e-mail]
> http://www.clustermatic.org/mailman/listinfo/linuxbios

[Steve Gehlbach]

Shubhangi Jadhav wrote:
> Hi,
>
> Could anyone tell me what are the .inc files found in the LinuxBIOS source?
>    Are these generated from the C code (for the sdram code I could see an
> association between the .c and corresponding .inc) and how ?

The .inc files are assembly language files that "stack up" or include, 
in order, on top of crt0.base.  These execute first, and eventually move 
the C-code (and decompress it if necessary) to RAM, ending at c_start.S, 
which jumps to the C-code.  The .inc files do things that are necessary 
as a prelude to running C, which needs RAM (ie, a stack).

Each .inc file must jump around its data, it is expected to execute top 
to bottom and flow to the next file included below it.

-Steve

[Shubhangi Jadhav]

how does crt0.base move to c_start.S. I did not find any reference to
c_start.S from crt0.base or any other .inc files included in crt0.base

-Shubhangi

-----Original Message-----
From: [e-mail]
[mailto:[e-mail]]On Behalf Of Steve Gehlbach
Sent: Saturday, March 15, 2003 10:44 PM
To: Shubhangi Jadhav
Cc: [e-mail]
Subject: Re: Help needed to understand code

Shubhangi Jadhav wrote:
> Hi,
>
> Could anyone tell me what are the .inc files found in the LinuxBIOS

source?
> Are these generated from the C code (for the sdram code I could see an
> association between the .c and corresponding .inc) and how ?

The .inc files are assembly language files that "stack up" or include,
in order, on top of crt0.base.  These execute first, and eventually move
the C-code (and decompress it if necessary) to RAM, ending at c_start.S,
which jumps to the C-code.  The .inc files do things that are necessary
as a prelude to running C, which needs RAM (ie, a stack).

Each .inc file must jump around its data, it is expected to execute top
to bottom and flow to the next file included below it.

-Steve

_______________________________________________
Linuxbios mailing list
[e-mail]
http://www.clustermatic.org/mailman/listinfo/linuxbios

[Steve Gehlbach]

Shubhangi Jadhav wrote:
> how does crt0.base move to c_start.S. I did not find any reference to
> c_start.S from crt0.base or any other .inc files included in crt0.base

The bottom of crt0.base jumps to c_start.S using loader "magic". 
c_start.S runs in ram in the C code address space.  crt0.base runs in rom.

-Steve

[Shubhangi Jadhav]

Hi,

Could you please explain to me the complete flow, right from the beginning
of execution of the assembly code. How does the assembly code jump to the C
code ? which is the jump instruction in crt0.base that makes it jump to
c_start.S

Thanks,
Shubhangi

-----Original Message-----
From: Steve Gehlbach [mailto:[e-mail]]
Sent: Monday, March 17, 2003 11:57 PM
To: Shubhangi Jadhav
Cc: [e-mail]
Subject: Re: Help needed to understand code

Shubhangi Jadhav wrote:
> how does crt0.base move to c_start.S. I did not find any reference to
> c_start.S from crt0.base or any other .inc files included in crt0.base

The bottom of crt0.base jumps to c_start.S using loader "magic".
c_start.S runs in ram in the C code address space.  crt0.base runs in rom.

-Steve