Re: Question on OPP table handling

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Kevin Hilman had written, on 10/05/2009 11:56 AM, the following:
"Premi, Sanjeev" <premi@xxxxxx> writes:

-----Original Message-----
From: Nishanth Menon [mailto:menon.nishanth@xxxxxxxxx] Sent: Saturday, October 03, 2009 8:35 PM
To: Premi, Sanjeev
Cc: linux-omap@xxxxxxxxxxxxxxx
Subject: Question on OPP table handling

Sanjeev Premi said the following on 10/01/2009 01:03 PM:
+struct omap_opp omap3_mpu_rate_table[] = {
+	{0, 0, 0},
+	/*OPP1*/
+	{S125M, VDD1_OPP1, 0x1E},
+	/*OPP2*/
+	{S250M, VDD1_OPP2, 0x26},
+	/*OPP3*/
+	{S500M, VDD1_OPP3, 0x30},
+	/*OPP4*/
+	{S550M, VDD1_OPP4, 0x36},
+	/*OPP5*/
+	{S600M, VDD1_OPP5, 0x3C},
+};
For those involved,
if we wanted to convert omap3_mpu_table[] into *omap3_mpu_table so that
we dynamically initialize it based on cpu type - what would be the
recommendations?
Nishanth,

Good idea!
As a table, previous patch enables it (not as intent, but due to syntax):

  >  +/* struct omap_opp_table - View OPP table as an object
  > + * @min: Minimum OPP id
  > + * @max: Maximim OPP id
  > + * @opps: Pointer to array defining the OPPs.
  > + *
  > + * An OPP table has varied length. Knowing minimum and maximum
  > + * OPP ids allow easy traversal.
  > + */
  > +struct omap_opp_table {
  > +       u8      min;
  > +       u8      max;
  > +       struct omap_opp* opps;
  > +};

But now, I think it would be good to have an API that can fill an opp_table:

int add_opp_definition(u8 id, u32 freq, u16 vsel);

...and, if an array is preferred, length can be set as:
int set_opp_table_length (u8 max);

I'm all for dynamic OPP setting, but not as an array.  A list should
probably be used.

Won't a list implementation cause more than necessary overhead? I agree that something like set_opp_table_length probably might be redundant in that case.


If I were to extend the discussion from other thread on toggling the valid OPPs
based on "enable_off_mode", these could be handy.

int set_opp_valid(bool flag);
bool is_opp_valid(void);

Yes, we need a concept of a valid OPP, not just for OFF mode, but for
OSWR and possibly for a full constraint framework as well.
Ack.
--
Regards,
Nishanth Menon
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