[U-Boot] [PATCH] 440spe MQ initialization

[Stefan Roese]

Hi Wolfgang,

On Friday 17 October 2008, Wolfgang Denk wrote:
> >  Set the MQ Read Passing & MCIF Cycle limits to the recommended by AMCC
> > values. This fixes the occasional 440SPe hard locking issues when the
> > 440SPe's dedicated DMA engines are used (e.g. by the h/w accelerated RAID
> > driver).
> >
> >  Previously the appropriate initialization had been made in Linux, by the
> > ppc440spe ADMA driver, which is wrong because modifying the MQ
> > configuration registers after normal operation has begun is not supported
> > and could have unpredictable results.
> >
> > Signed-off-by: Yuri Tikhonov <yur at emcraft.com>
> > ---
> >  cpu/ppc4xx/44x_spd_ddr2.c      |   10 ++++++----
> >  include/asm-ppc/ppc4xx-sdram.h |    5 +++++
> >  2 files changed, 11 insertions(+), 4 deletions(-)
>
> I must admit that I lost  track  in  the  discussion  following  this
> posting  what  the real state of affairs is now. Do we need to change
> anything in U-Boot, or not, and why not?

I also lost track of whats really needed, I'm afraid. That's why I asked about 
this a few weeks ago. Here an extract from the last mail:

On Thursday 25 September 2008, Prodyut Hazarika wrote:
> > So please let me know if Yuri's original MQ patch should be applied and
> > if there is another PLB arbiter patch that should be applied too.
>
> Yuri's patch does the following
>  - set RLPM (read passing limit) bits in MQ register to 1,
>  - set  WRCL (MCIF cycle limit) in MQ registers to 1.
> In my testing, as far as I can remember, these values were set to 1 by
> default. I had tested with Canyonlands, Kilauea, Katmai and Glacier boards.
> So unless Yuri found that these values were not default values in some
> processor, Yuri's patch should be applied.

So it seems that the current code relies on some already preset (default) 
values in those registers. I don't really like this. I'll try to provide a 
patch that configures those registers completely in a short while.

It would be great if Yuri could test this on a target to see if we are still 
missing something.

Best regards,
Stefan

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