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From: Grant Likely <grant.likely@secretlab.ca>
Date: Tue, 2 Mar 2010 13:06:44 -0700
Message-ID: <fa686aa41003021206v773b30d1vef6362704dca9e61@mail.gmail.com>
Subject: Re: [Patch] mpc5200b: improve baud rate calculation (reach high baud
	rates, better accuracy)
To: =?ISO-8859-1?Q?Albrecht_Dre=DF?= <albrecht.dress@arcor.de>
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On Tue, Mar 2, 2010 at 1:09 AM, Albrecht Dre=DF <albrecht.dress@arcor.de> w=
rote:
>> > + =A0 /* Check only once if we are running on a mpc5200b or not */
>> > + =A0 if (is_mpc5200b =3D=3D -1) {
>> > + =A0 =A0 =A0 =A0 =A0 struct device_node *np;
>> > +
>> > + =A0 =A0 =A0 =A0 =A0 np =3D of_find_compatible_node(NULL, NULL, "fsl,=
mpc5200b-immr");
>>
>> This should be handled using a new compatible-entry
>> "fsl,mpc5200b-psc-uart".
>
> I agree that this would be a lot cleaner, but it's also a lot more intrus=
ive. =A0CC'ing the device tree discussion list here... comments, please!!

fsl,mpc5200b-psc-uart is already in the compatible list for all
MPC500b boards currently in the kernel tree.

>> > + =A0 =A0 =A0 =A0 =A0 if (np) {
>> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 is_mpc5200b =3D 1;
>> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 dev_dbg(&op->dev, "mpc5200b: usi=
ng /4 prescaler\n");
>>
>> Does this message respect the fallback case?
>
> See comment above...
>
>> You could also have a set_divisor-function for 5200 and 5200B and set it
>> here
>> in the function struct (one reason less for the static ;))
>
> Hmmm, but then I would need a 'static struct psc_ops mpc5200b_psc_ops', w=
here only two functions differ from the generic 52xx struct as it is implem=
ented now. =A0Using the static int needs less space. =A0However, in combina=
tion with the new compatible entry, it would of course make sense.
>
> Again, any insight from the device tree gurus would be appreciated!

Wolfram is correct, you should set the correct divisor function in the
ops structure.  Much clearer code that way.

g.