Re: Some comments on Linux-OMAP tree by Russell King

Re: Some comments on Linux-OMAP tree by Russell King

[Dirk Behme]

Romain Goyet wrote:
 > By the way, Russell also added this :
 >
 >>Hmm, I notice that omap folk are _still_ buggering up the MMC core in
 >>relation to mmc.c.  It'd also be nice of omap folk could conform to
 >>the agreed usage of clk_use/unuse vs clk_enable/disable as documented
 >>in the header file.  The clock framework *relies* on everyone
 >>following the rules.  Frustrated sigh.

Everybody who is interested in this, "Clock framework" thread on 
linux-arm-kernel starting with (still ongoing)

http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2005-December/032851.html

Dirk

Some comments on Linux-OMAP tree by Russell King

[Romain Goyet]

Hello guys,
  I've had recently many problems on my Palm Tungsten E. In
particular, it was crashing when I ran "local_flush_tlb_all()", in
arch/arm/mm/init.c. I asked for help on the ARM-Linux mailing list,
and here is what Russell finally told me :

> Argh, omap sets up a mapping and then immediately tries to access
> IO space.  If some of the cache lines for the page tables were already
> in the cache, or you are using a write-alloc cache, that's not going
> to work - the mappings will not be visible to the MMU.  Note carefully
> the comment:
>
>       /*
>        * Finally flush the caches and tlb to ensure that we're in a
>        * consistent state wrt the writebuffer.  This also ensures that
>        * any write-allocated cache lines in the vector page are written
>        * back.  After this point, we can start to touch devices again.
>        */
>
> and omap is accessing devices _prior_ to that point. 8(
>
> This is most likely the reason why you're seeing boot failures.

What do you think about this ? In particular, I think he is talking about this :
in arch/arm/mach-omap1/io.c

        /* We have to initialize the IO space mapping before we can run
         * cpu_is_omapxxx() macros. */

This is true, but we have to wait _as well_ that
mm/init.c:devicemaps_init() has terminated. I would have proposed a
patch, but it looks like many functions, like
omap_sram_init();
and
omap1_clk_init();
Use cpu_is_omapXXXX() functions.

Do you have any idea for a workaround ?

Thanks in advance

Romain Goyet.


By the way, Russell also added this :

> Hmm, I notice that omap folk are _still_ buggering up the MMC core in
> relation to mmc.c.  It'd also be nice of omap folk could conform to
> the agreed usage of clk_use/unuse vs clk_enable/disable as documented
> in the header file.  The clock framework *relies* on everyone following
> the rules.  Frustrated sigh.

Re: Some comments on Linux-OMAP tree by Russell King

[Tony Lindgren]

Hi,

Back from vacation now.

* Romain Goyet <r.goyet@gmail.com> [051214 06:26]:
> Hello guys,
>   I've had recently many problems on my Palm Tungsten E. In
> particular, it was crashing when I ran "local_flush_tlb_all()", in
> arch/arm/mm/init.c. I asked for help on the ARM-Linux mailing list,
> and here is what Russell finally told me :
> 
> > Argh, omap sets up a mapping and then immediately tries to access
> > IO space.  If some of the cache lines for the page tables were already
> > in the cache, or you are using a write-alloc cache, that's not going
> > to work - the mappings will not be visible to the MMU.  Note carefully
> > the comment:
> >
> >       /*
> >        * Finally flush the caches and tlb to ensure that we're in a
> >        * consistent state wrt the writebuffer.  This also ensures that
> >        * any write-allocated cache lines in the vector page are written
> >        * back.  After this point, we can start to touch devices again.
> >        */
> >
> > and omap is accessing devices _prior_ to that point. 8(
> >
> > This is most likely the reason why you're seeing boot failures.
> 
> What do you think about this ? In particular, I think he is talking about this :
> in arch/arm/mach-omap1/io.c
> 
>         /* We have to initialize the IO space mapping before we can run
>          * cpu_is_omapxxx() macros. */
> 
> This is true, but we have to wait _as well_ that
> mm/init.c:devicemaps_init() has terminated. I would have proposed a
> patch, but it looks like many functions, like
> omap_sram_init();
> and
> omap1_clk_init();
> Use cpu_is_omapXXXX() functions.
> 
> Do you have any idea for a workaround ?

I'll take a look at it. The omap specific init could use some clean up.
 
> Thanks in advance
> 
> Romain Goyet.
> 
> 
> By the way, Russell also added this :
> 
> > Hmm, I notice that omap folk are _still_ buggering up the MMC core in
> > relation to mmc.c.  It'd also be nice of omap folk could conform to
> > the agreed usage of clk_use/unuse vs clk_enable/disable as documented
> > in the header file.  The clock framework *relies* on everyone following
> > the rules.  Frustrated sigh.

Yeah, we should clean up the MMC driver and send it upstream. There are
some buggy card fixes for mmc.c that should also be sent upstream.

Regards,

Tony