On Wed, Nov 25, 2020 at 02:24:19PM -0500, Jim Quinlan wrote:
> + for (i = 0; i < PCIE_REGULATORS_MAX; i++) {
> + ep_reg = devm_regulator_get_optional(dev, ep_regulator_names[i]);
> + if (IS_ERR(ep_reg)) {
Does PCI allow supplies to be physically absent? If not then the driver
shouldn't be using regulator_get_optional() and much of the code here
can be deleted.
> +static void brcm_set_regulators(struct brcm_pcie *pcie, bool on)
> +{
This is open coding the regulator bulk APIs.
On Thu, Nov 26, 2020 at 6:49 AM Mark Brown <[email protected]> wrote:
>
> On Wed, Nov 25, 2020 at 02:24:19PM -0500, Jim Quinlan wrote:
>
> > + for (i = 0; i < PCIE_REGULATORS_MAX; i++) {
> > + ep_reg = devm_regulator_get_optional(dev, ep_regulator_names[i]);
> > + if (IS_ERR(ep_reg)) {
>
> Does PCI allow supplies to be physically absent? If not then the driver
> shouldn't be using regulator_get_optional() and much of the code here
> can be deleted.
Hi Mark,
First, as an aside, I'm a little confused about the purpose of
devm_regulator_get_optional(...); the other xxx_get_optional() calls
I am familiar with (eg clock, reset, gpio) return NULL if the desired
item does not exist, and then NULL can be used as a valid pointer for
the rest of the API. Not so here.
At any rate, our SOCs are placed in a variety of boards which
implement the PCIe RC-EP connection as they wish. From the PCIe
driver's point of view, the type of power supply that needs to be
turned on is specified in the DT and they cannot be hard coded by the
driver. I've listed all of the four possibilities; typically one,
maybe two will be specified, but never all of them. In addition,
sometimes a regulator is hard wired on and not even controllable by
the PCIe controller.
>
> > +static void brcm_set_regulators(struct brcm_pcie *pcie, bool on)
> > +{
>
> This is open coding the regulator bulk APIs.
Except that a bulk regulator "get" requires that all supplies are
present. I would have to first scan the node's properties for the
"-supply" properties and fill in the bulk regulator structure. I'm
fine with doing that.
However, a previous incarnation of this commit was reviewed by RobH,
and if I understood him correctly he wanted the actual names of the
possible regulators to be used and specified in the bindings doc. I
just followed the example of "pcie-rockchip-host.c" whose bindings doc
was reviewed by RobH.
Regards,
Jim Quinlan
Broadcom STB
On Fri, Nov 27, 2020 at 03:26:53PM -0500, Jim Quinlan wrote:
> On Thu, Nov 26, 2020 at 6:49 AM Mark Brown <[email protected]> wrote:
> > Does PCI allow supplies to be physically absent? If not then the driver
> > shouldn't be using regulator_get_optional() and much of the code here
> > can be deleted.
> First, as an aside, I'm a little confused about the purpose of
> devm_regulator_get_optional(...); the other xxx_get_optional() calls
> I am familiar with (eg clock, reset, gpio) return NULL if the desired
> item does not exist, and then NULL can be used as a valid pointer for
> the rest of the API. Not so here.
The other APIs that cloned the regulator API don't have the dummy
support that the regulator has and unfortunately changed the sense a bit
there.
> > > +static void brcm_set_regulators(struct brcm_pcie *pcie, bool on)
> > > +{
> > This is open coding the regulator bulk APIs.
> Except that a bulk regulator "get" requires that all supplies are
> present. I would have to first scan the node's properties for the
> "-supply" properties and fill in the bulk regulator structure. I'm
> fine with doing that.
No, you should never do that. If the supplies can be physically absent
then you should use regulator_get_optional() which allows you to do
whatever needs doing to configure the hardware for the missing supply.
If it's just that the supply may not be described in the DT but has to
be there for the device to operate then the code should use the normal
regualtor APIs - a dummy regulator will be provided if there's no supply
described.
> However, a previous incarnation of this commit was reviewed by RobH,
> and if I understood him correctly he wanted the actual names of the
> possible regulators to be used and specified in the bindings doc. I
> just followed the example of "pcie-rockchip-host.c" whose bindings doc
> was reviewed by RobH.
That is just plain bad code, the binding may well be fine but I can't
see any excuse for that driver to be using _optional() there.
Another subsystem I'm going to have to keep an eye on :(