Apologies for the long post, but given the absence of many/any voltage
regulator drivers - especially PMICs - I feel I need to get this all sorted and
agreed. So I have looked long and hard at the Nuttx files and Linux
documentation and to see if I have got it right I would like to see if the
following descriptions of the Nuttx struct fields make sense.
struct regulator_desc_s
{
const char *name; /* Friendly name that will be used to
get/set/etc a given regulator. For example "VCC" */
unsigned int n_voltages; /* The number of discrete voltage selector
steps this regulator allows. 0 if linear mapping is to be used instead */
unsigned int vsel_reg; /* The device-specific regulator
"channel", or GPIO output, or similar, for this regulator */
unsigned int vsel_mask; /* Mask, if relevant, to use with vsel_reg*/
unsigned int enable_reg; /* Device specific enable register, if
relevant, for this regulator */
unsigned int enable_mask; /* Mask, if relevant, to use with enable_reg*/
unsigned int enable_time; /* Time taken for the regulator voltage output
voltage to stabilise after being enabled, in microseconds */
unsigned int ramp_delay; /* Set the ramp delay for the regulator. The
driver should select ramp delay equal to or less than(closest) ramp_delay */
unsigned int uv_step; /* Voltage increase with each selector if
linear mapping. 0 if only selector steps are allowed */
unsigned int min_uv; /* Smallest voltage consumers may set*/
unsigned int max_uv; /* Largest voltage consumers may set */
unsigned int apply_uv; /* ?? SEE BELOW [1] */
bool boot_on; /* Set if the regulator is enabled when the
system is initially started SEE BELOW [2].
If the regulator is not enabled by the
hardware or bootloader then it will be enabled when the constraints are applied
*/
};
[1] "apply_uv" is a bool in Linux but an int in Nuttx. In Linux it tells you
whether the "constraint" voltage is applied during init. I think it should be a
bool in Nuttx too? With the ACT8945A, for example, REG1-5 power on by default,
whereas REG6 and 7 do not. The REG1-5 will report back "0" and REG6/6 "1" in
boot_on.
[2] It is not clear, either in Linux or Nuttx, what the "constraint voltage"
that is applied during init will be. Perhaps the NuttX intent is - or should be
- to use an actual value here (hence the int?) which will be applied during
init IF "boot_on" is set on (suggesting it is a parameter that should be passed
TO the regulator register/init function not filled in BY it?
If this is all (nearly) correct, then I think the call to register a regulator
(from board_bringup, say) needs to initialise the following variables in the
regulator_desc_s struct that's passed:
- name For example, in my design, REG1 is "VIODDR"
- vsel_reg In my example it is "REG1" and I need to tell
the ACT8945A driver this.
- vsel_mask (if relevant). Not relevant in my case
- enable_reg, if relevant. Not relevant in my case.
- enable_mask, if relevant. Not relevant in my case.
So we would have (for this i2c device, at least):
FAR struct regulator_desc_s *act8945a_desc_s;
FAR struct i2c_master_s *act89945a_i2c ;
int ret;
act89945a_i2c = board_i2c_init(busno);
if (!act8945a_i2c)
{
Blah blah;
}
act8945a_desc_s->name = "VIODDR";
act8945a_desc_s->vsel_reg = 1;
ret = act8945a_device_init(act8945a_desc_s, act8945a_i2c);
if (ret < 0)
{
Blah blah;
}
The init/register routine will fill in the missing blanks in the structure and
we can go from there to set it up. When needed in the user app, we can do a
"regulator get" to see what we've got and change things as needed.
Does that sound right or am I way off the mark?
If I'm nearly right I might add that I believe there are useful members of the
regulator_desc_s structure missing, such as "active_discharge" that's useful
for the ACT8945A. Maybe also "always on" which tells the driver NEVER to turn
this one off - rather important for PMIC devices I would say, although NuttX
apps aren't quite so likely to mess around with regulators on these custom
boards. I can add these to the struct, of course, as I write my driver.
Final observation - Linux documentation quite clearly states microvolts for all
voltage parameters. That means a simple 3V3 regulator will be set up with the
value 3300000 passed to the functions, so it has to use uint32_t. Maybe that
makes sense for Linux, but perhaps for Nuttx it should be in millivolts? I see
there's a driver for an AXP202 device and that is clearly assuming millivolts?
