public inbox for linuxppc-dev@ozlabs.org 
 help / color / mirror / Atom feed

From: "Albrecht Dreß" <albrecht.dress@arcor•de>
To: w.sang@pengutronix•de
Cc: linuxppc-dev@ozlabs•org, devicetree-discuss@lists•ozlabs.org
Subject: Re: [Patch] mpc5200b: improve baud rate calculation (reach high baud rates, better accuracy)
Date: Tue, 2 Mar 2010 09:56:48 +0100 (CET)	[thread overview]
Message-ID: <22132814.1267520208614.JavaMail.ngmail@webmail14.arcor-online.net> (raw)
In-Reply-To: <20100302082858.GA4087@pengutronix.de>

Hi Wolfram:

[snip]
> > Yes, but I do all /calculations/ with the /4 prescaler for higher
> accuracy.
> > If the divisor exceeds the available 16 bits of the counter reg, I roun=
d
> > (divisor / 8) to use the /32 prescaler.  Think of a 19-bit counter valu=
e,
> > where I can choose to use either the lower or the higher 16 bits for th=
e
> > counter reg.
>=20
> Okay, now I got it. (Maybe this is an indication for another comment abov=
e
> the
> set divisor function?)

O.k., I will add that comment...

> > Remember also that using the higher 16 bits (/32 prescaler) is
> > probably the exceptional case - with an IPB frequency of 132 MHz this
> will
> > happen only for standard baud rates B300 and slower.
>=20
> Even the rare cases have to be correct ;)

I agree - will make the debug output and comments clearer...

[snip]
> > > This should be handled using a new compatible-entry
> > > "fsl,mpc5200b-psc-uart".
> >=20
>=20
> > I agree that this would be a lot cleaner, but it's also a lot more
> intrusive.
> > CC'ing the device tree discussion list here... comments, please!!
>=20
> Why intrusive? Maybe I miss something?

Not for the source file, but for all the dts files, if they want to benefit=
 from the detection of the '5200B.  Basically, *all* files have to be check=
ed and touched if necessary.  Again, I agree that this would be the clean a=
pproach, but I wanted to avoid that effort.  Grant???

[snip]
> Leave those two function pointers empty and fill them during probe (probe
> has
> access to the compatible-property it was matched against, see its
> arguments).
> So it should be a matter of:
>=20
> if (matched_property =3D=3D 5200b)
> =09ops->func =3D this_one;
> else
> =09ops->func =3D that_one;

Umm, yes, that's true of course.  Will pick it up.

Thanks, Albrecht.

Tolle Dekollet=E9s oder scharfe Tatoos? Vote jetzt ... oder mach selbst mit=
 und zeige Deine Schokoladenseite
bei Topp oder Hopp von Arcor: http://www.arcor.de/rd/footer.toh

next prev parent reply	other threads:[~2010-03-02  8:56 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-02  8:09 [Patch] mpc5200b: improve baud rate calculation (reach high baud rates, better accuracy) Albrecht Dreß
2010-03-02  8:28 ` Wolfram Sang
2010-03-02  8:56   ` Albrecht Dreß [this message]
2010-03-02 15:27     ` Wolfram Sang
2010-03-02 20:12     ` Grant Likely
2010-03-02 20:06 ` Grant Likely
  -- strict thread matches above, loose matches on Subject: below --
2010-03-01 18:11 Albrecht Dreß
2010-03-02  0:32 ` Wolfram Sang
2010-03-02 20:22 ` Grant Likely

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=22132814.1267520208614.JavaMail.ngmail@webmail14.arcor-online.net \
    --to=albrecht.dress@arcor$(echo .)de \
    --cc=devicetree-discuss@lists$(echo .)ozlabs.org \
    --cc=linuxppc-dev@ozlabs$(echo .)org \
    --cc=w.sang@pengutronix$(echo .)de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox