Hi Wolfram!
Thanks a lot for your comments!
[snip]
quoted
+ * as the chip can be only either a 5200B or not. */
+static int is_mpc5200b =3D -1;
+
+
=20
One empty line too much. Maybe we can also get rid of the static later in
the
process, but first things first.
Ooops....
[snip]
quoted
+=09if (is_mpc5200b =3D=3D 1)
+=09=09return mpc5xxx_get_bus_frequency(p) * 4;
+=09else
+=09=09return mpc5xxx_get_bus_frequency(p) / 2;
=20
Isn't this wrong? You can also have /32 on the 5200B (the fallback).
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 round =
(divisor / 8) to use the /32 prescaler. Think of a 19-bit counter value, w=
here I can choose to use either the lower or the higher 16 bits for the cou=
nter reg. Remember also that using the higher 16 bits (/32 prescaler) is p=
robably the exceptional case - with an IPB frequency of 132 MHz this will h=
appen only for standard baud rates B300 and slower.
[snip]
quoted
+=09/* Check only once if we are running on a mpc5200b or not */
+=09if (is_mpc5200b =3D=3D -1) {
+=09=09struct device_node *np;
+
+=09=09np =3D of_find_compatible_node(NULL, NULL, "fsl,mpc5200b-immr");
=20
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 intrusiv=
e. CC'ing the device tree discussion list here... comments, please!!
quoted
+=09=09if (np) {
+=09=09=09is_mpc5200b =3D 1;
+=09=09=09dev_dbg(&op->dev, "mpc5200b: using /4 prescaler\n");
=20
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', whe=
re only two functions differ from the generic 52xx struct as it is implemen=
ted now. Using the static int needs less space. However, in combination w=
ith the new compatible entry, it would of course make sense.
Again, any insight from the device tree gurus would be appreciated!
Thanks, Albrecht.
Tolle Dekollet=E9s oder scharfe Tatoos? Vote jetzt ... oder mach selbst mit=
und zeige Deine Schokoladenseite
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[snip]
quoted
quoted
+ if (is_mpc5200b == 1)
+ return mpc5xxx_get_bus_frequency(p) * 4;
+ else
+ return mpc5xxx_get_bus_frequency(p) / 2;
Isn't this wrong? You can also have /32 on the 5200B (the fallback).
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 round
(divisor / 8) to use the /32 prescaler. Think of a 19-bit counter value,
where I can choose to use either the lower or the higher 16 bits for the
counter reg.
Okay, now I got it. (Maybe this is an indication for another comment above the
set divisor function?)
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.
Even the rare cases have to be correct ;)
[snip]
quoted
quoted
+ /* Check only once if we are running on a mpc5200b or not */
+ if (is_mpc5200b == -1) {
+ struct device_node *np;
+
+ np = 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 intrusive.
CC'ing the device tree discussion list here... comments, please!!
Why intrusive? Maybe I miss something?
quoted
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', where
only two functions differ from the generic 52xx struct as it is implemented
now. Using the static int needs less space. However, in combination with
the new compatible entry, it would of course make sense.
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:
if (matched_property == 5200b)
ops->func = this_one;
else
ops->func = that_one;
Regards,
Wolfram
--
Pengutronix e.K. | Wolfram Sang |
Industrial Linux Solutions | http://www.pengutronix.de/ |
On Tue, Mar 2, 2010 at 1:09 AM, Albrecht Dre=DF [off-list ref] w=
rote:
quoted
quoted
+ =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");
quoted
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.
quoted
quoted
+ =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");
quoted
Does this message respect the fallback case?
See comment above...
quoted
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.