[U-Boot] common/xyzmodem.c, ymodem, slow behavior receiving bytes
Wolfgang Denk
wd at denx.de
Tue Nov 13 08:09:19 CET 2012
Dear Angelo Dureghello,
please don't top-post / full quote.
In message <20121113001651.GA21177 at angel3> you wrote:
>
> seems that mcf5307, working at 90Mhz, is not fast enough when "-Os -g"
> compile options are set.
>
> I changed for test config.mk from
>
> DBGFLAGS= -g # -DDEBUG
> OPTFLAGS= -Os #-fomit-frame-pointer
>
> into
>
> DBGFLAGS= #-g # -DDEBUG
> OPTFLAGS= -O2 #-Os #-fomit-frame-pointer
>
> common compiles now with -O2 and ymodem works fine again at 115200.
Removing -g makes no sense in this cotext. It has no impact on the
generated code.
I am really surprised about your claim that the -O2 compiled code is
actually running faster than the -Os compiled one on a low-end system
as yours (90 MHz CPU clock, 8 kB cache size).
Which exact tool chain are you using to build the code?
> Also, i don't understand why "-g" is set by default.
It is set because it is useful to some (those in the need of debugging
their code) and does not hurt others.
> Is there a way to override/customize this options for this cpu ?
I am not convinced that it makes sense to change settings on a per-cpu
base. A 90 MHz CPU should be more than sufficient to receive data at
115kbps. I can only compare against 50 MHz PowerQuicc I systems
(which is about the lowest end machines I have at hands now), and
there no such problem exists.
It would be good to understand exactly where the problem is coming
from. I don't think that the -Os setting is the core of the problem;
I tend to suspect rather your tool chain or your serial driver or such.
> Or i have to definitely step down to 57600 ?
There should be no need for that.
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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