On Fri, Dec 11, 2009 at 01:41:46AM +0100, ext Nishanth Menon wrote:
> Kevin Hilman had written, on 12/10/2009 05:25 PM, the following:
> Thanks for the acks..
>
> > Nishanth Menon <nm@xxxxxx> writes:
> [...]
>
> >> diff --git a/arch/arm/plat-omap/include/plat/opp.h b/arch/arm/plat-omap/include/plat/opp.h
> >> new file mode 100644
> >> index 0000000..341c02b
>
> [...]
>
> >> +/**
> >> + * struct omap_opp - OMAP OPP description structure
> >> + * @enabled: true/false - marking this OPP as enabled/disabled
> >> + * @rate: Frequency in hertz
> >> + * @opp_id: (DEPRECATED) opp identifier
> >> + * @vsel: Voltage in volt processor level(this usage is
> >> + * DEPRECATED to use Voltage in microvolts in future)
> >> + * uV = ((vsel * 12.5) + 600) * 1000
> >> + *
> >> + * This structure stores the OPP information for a given domain.
> >> + * Due to legacy reasons, this structure is currently exposed and
> >> + * will soon be removed elsewhere and will only be used as a handle
> >> + * from the OPP internal referencing mechanism
> >> + */
> >> +struct omap_opp {
> >> + bool enabled;
> >> + unsigned long rate;
> >> + u8 opp_id __deprecated;
> >> + u16 vsel;
> >
> > How about we add 'u32 voltage' here and mark vsel as __deprecated. Then
> > we no longer need both an 'struct omap_opp' and a 'struct omap_opp_def'.
> >
> > Or even better, with the uv <--> vsel conversion macros you added,
> > couldn't we alrady define the OPPs in terms of voltage, and drop the
> > vsel already?
>
> we should do that once we fix SR + resource34xx (underworks) - they
> directly use them and I kept my "status quo" rule switch on ;). Once it
> is done, vsel becomes voltage and an unsigned long. and we can manage it
> inside opp.c anyway we choose. For this starting set, I dont think we
> should do this.
I'm OK if you have the plan to do it in steps. But might be useful to have some
REVISIT / TODO comment on top of things you know you are going to change afterwards.
It is not mandatory, but it helps to keep track of what is in your plans.
>
> [...]
> >
> >> +/**
> >> + * opp_find_freq_exact() - search for an exact frequency
> >> + * @oppl: OPP list
> >> + * @freq: frequency to search for
> >> + * @enabled: enabled/disabled OPP to search for
> >> + *
> >> + * searches for the match in the opp list and returns handle to the matching
> >> + * opp if found, else returns ERR_PTR in case of error and should be handled
> >> + * using IS_ERR.
> >> + *
> >> + * Note enabled is a modifier for the search. if enabled=true, then the match is
> >> + * for exact matching frequency and is enabled. if true, the match is for exact
> >> + * frequency which is disabled.
> >> + */
> >> +struct omap_opp *opp_find_freq_exact(struct omap_opp *oppl,
> >> + unsigned long freq, bool enabled);
> >
> > ack
> >
> > I think we could drop the _exact, and just call it opp_find_freq(), but I'm
> > ok either way.
> shrug.. kinda matches with _approx .. it improves readability esp when
> people look at a usage code 6 months from now and question what
> find_freq is doing and get confused about freq_approx
>
> [...]
>
> >> +/**
> >> + * struct omap_opp_def - OMAP OPP Definition
> >> + * @enabled: True/false - is this OPP enabled/disabled by default
> >> + * @freq: Frequency in hertz corresponding to this OPP
> >> + * @u_volt: Nominal voltage in microvolts corresponding to this OPP
> >> + *
> >> + * OMAP SOCs have a standard set of tuples consisting of frequency and voltage
> >> + * pairs that the device will support per voltage domain. This is called
> >> + * Operating Points or OPP. The actual definitions of OMAP Operating Points
> >> + * varies over silicon within the same family of devices. For a specific
> >> + * domain, you can have a set of {frequency, voltage} pairs and this is denoted
> >> + * by an array of omap_opp_def. As the kernel boots and more information is
> >> + * available, a set of these are activated based on the precise nature of
> >> + * device the kernel boots up on. It is interesting to remember that each IP
> >> + * which belongs to a voltage domain may define their own set of OPPs on top
> >> + * of this - but this is handled by the appropriate driver.
> >> + */
> >> +struct omap_opp_def {
> >> + bool enabled;
> >> + unsigned long freq;
> >> + u32 u_volt;
> Comment to self: I should really make the u32 as unsigned long to be in
> sync with what is used elsewhere..(get_voltage)
>
> >> +};
> >
> > See above comment on 'struct omap_opp'. I think these two should be
> > combined.
> >
> > I think the initial intent of having them separated so that the
> > internal struct of 'struct omap_opp' could eventually move to the C
> > file was the original intent, but I think it aids readability to just
> > have a single OPP struct.
>
> In a few weeks we wont have the struct omap_opp exposed out(once all the
> cleanups are done).. at that point, how would one define an OPP and
> expect to get an handle which they cannot manipulate?
>
> >
> >> +/* Initialization wrapper */
> >> +#define OMAP_OPP_DEF(_enabled, _freq, _uv) \
> >> +{ \
> >> + .enabled = _enabled, \
> >> + .freq = _freq, \
> >> + .u_volt = _uv, \
> >> +}
> >
> > nice
> >
> >> +/* Terminator for the initialization list */
> >> +#define OMAP_OPP_DEF_TERMINATOR OMAP_OPP_DEF(0, 0, 0)
> >
> > I'd just drop this and use OMAP_OPP_DEF(0, 0, 0) directly in
> > the table.
>
> Am ok with either (I dont like additional #defs). but terminator helps
> redability a bit though (debatable).. any reasons why u'd like it 0,0,0?
> >
> >> +/**
> >> + * opp_init_list() - Initialize an opp list from the opp definitions
> >> + * @opp_defs: Initial opp definitions to create the list.
> >> + *
> >> + * This function creates a list of opp definitions and returns a handle.
> >> + * This list can be used to further validation/search/modifications. New
> >> + * opp entries can be added to this list by using opp_add().
> >> + *
> >> + * In the case of error, ERR_PTR is returned to the caller and should be
> >> + * appropriately handled with IS_ERR.
> >> + */
> >> +struct omap_opp __init *opp_init_list(const struct omap_opp_def *opp_defs);
> >
> > My original suggestion was that opp_init_list() simply creates a new
> > but empty list. Adding OPPs should be done using opp_add().
> >
> > I guess I'm OK with having the 'bulk add' feature of init_list() but
> > would rather see a single way to add OPPs.
> Reasons why to have a buld add feature in init:
> a) There is opp_add below which allows u to add single opp
> b) In terms of walk thru code duplication (once this gets used accross
> OMAPs) it is essentially the same thing we do (add each OPP definition
> for a domain)..
> c) you dont incur function call latencies. (ok not a big deal.. but still).
>
> >
> >> +/**
> >> + * opp_add() - Add an OPP table from a table definitions
> >> + * @oppl: List to add the OPP to
> >> + * @opp_def: omap_opp_def to describe the OPP which we want to add to list.
> >> + *
> >> + * This function adds an opp definition to the opp list and returns
> >> + * a handle representing the new OPP list. This handle is then used for further
> >> + * validation, search, modification operations on the OPP list.
> >> + *
> >> + * This function returns the pointer to the allocated list through oppl if
> >> + * success, else corresponding ERR_PTR value. Caller should NOT free the oppl.
> >> + * opps_defs can be freed after use.
> >> + *
> >> + * NOTE: caller should assume that on success, oppl is probably populated with
> >> + * a new handle and the new handle should be used for further referencing
> >> + */
> >> +struct omap_opp *opp_add(struct omap_opp *oppl,
> >> + const struct omap_opp_def *opp_def);
> >
> > c.f. proposal to drop omap_opp_def.
> explained above.
>
> >
> > otherwise, ack.
> >
>
> --
> Regards,
> Nishanth Menon
--
Eduardo Valentin
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