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Message-ID: <20111024130429.GD1755@S2100-06.ap.freescale.net>
Date: Mon, 24 Oct 2011 21:04:31 +0800
From: Shawn Guo <shawn.guo@...escale.com>
To: Grant Likely <grant.likely@...retlab.ca>
CC: Rajendra Nayak <rnayak@...com>,
<broonie@...nsource.wolfsonmicro.com>, <patches@...aro.org>,
<tony@...mide.com>, <devicetree-discuss@...ts.ozlabs.org>,
<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
<lrg@...com>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/5] regulator: helper routine to extract
regulator_init_data
On Mon, Oct 24, 2011 at 11:24:11AM +0200, Grant Likely wrote:
> On Fri, Oct 21, 2011 at 04:23:12PM +0800, Shawn Guo wrote:
> > On Thu, Oct 20, 2011 at 05:39:32PM +0530, Rajendra Nayak wrote:
> > > On Thursday 20 October 2011 11:44 AM, Shawn Guo wrote:
> > > >On Thu, Oct 20, 2011 at 10:48:58AM +0530, Rajendra Nayak wrote:
> > > >>>Let's look at mc13892-regulator driver. There are 23 regulators defined
> > > >>>in array mc13892_regulators. Needless to say, there is a dev behind
> > > >>>mc13892-regulator driver. And when getting probed, this driver will
> > > >>>call regulator_register() to register those 23 regulators individually.
> > > >>>That said, for non-dt world, we have 1 + 23 'dev' with that 1 as the
> > > >>>parent of all other 23 'dev' (wrapped by regulator_dev). But with the
> > > >>>current DT implementation, we will have at least 1 + 23 * 2 'dev'.
> > > >>>These extra 23 'dev' is totally new with DT.
> > > >>>
> > > >>
> > > >>but thats only because the mc13892-regulator driver is implemeted in
> > > >>such a way that all the regulators on the platform are bundled in as
> > > >>*one* device.
> > > >
> > > >I did not look into too many regulator drivers, but I expect this is
> > > >way that most regulator drivers are implemented in. Having
> > > >mc13892-regulator being probed 23 times to register these 23 regulators
> > > >just makes less sense to me.
> > > >
> > > >>It would again depend on how you would pass these from
> > > >>the DT, if you indeed stick to the same way of bundling all regulators
> > > >>as one device from DT, the mc13892-regulator probe would just get called
> > > >>once and there would be one device associated, no?
> > > >>
> > > >Yes, I indeed would stick to the same way of bundling the registration
> > > >of all regulators with mc13892-regulator being probed once. The problem
> > > >I have with the current regulator core DT implementation is that it
> > > >assumes the device_node of rdev->dev (dev wrapped in regulator_dev) is
> > > >being attached to rdev->dev.parent rather than itself. Back to
> > > >mc13892-regulator example, that said, it requires the dev of
> > > >mc13892-regulator have the device_node of individual regulator attached
> > > >to. IOW, the current implementation forces mc13892-regulator to be
> > > >probed 23 times to register those 23 regulators. This is wrong to me.
> > >
> > > I think I now understand to some extent the problem that you seem to be
> > > reporting. It is mainly with drivers which bundle all regulators and
> > > pass them as one device and would want to do so with DT too.
> > >
> > > however I am still not clear on how what you seem to suggest would
> > > solve this problem. Note that not all drivers do it this way, and
> > > there are drivers where each regulator is considered as one device
> > > and I suspect they would remain that way with DT too. And hence we
> > > need to support both.
> > >
> > > Do you have any RFC patch/code which could explain better what you are
> > > suggesting we do here?
> > > >
> > Here is what I changed based on your patches. It only changes
> > drivers/regulator/core.c.
> >
> > ---8<-------
> > diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> > index 9a5ebbe..8fe132d 100644
> > --- a/drivers/regulator/core.c
> > +++ b/drivers/regulator/core.c
> > @@ -1211,7 +1211,7 @@ static struct regulator *_regulator_get(struct device *dev, const char *id,
> > node = of_get_regulator(dev, id);
> > if (node)
> > list_for_each_entry(rdev, ®ulator_list, list)
> > - if (node == rdev->dev.parent->of_node)
> > + if (node == rdev->dev.of_node)
> > goto found;
> > }
> > list_for_each_entry(map, ®ulator_map_list, list) {
> > @@ -2642,9 +2642,6 @@ struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
> > regulator_desc->type != REGULATOR_CURRENT)
> > return ERR_PTR(-EINVAL);
> >
> > - if (!init_data)
> > - return ERR_PTR(-EINVAL);
> > -
> > /* Only one of each should be implemented */
> > WARN_ON(regulator_desc->ops->get_voltage &&
> > regulator_desc->ops->get_voltage_sel);
> > @@ -2675,12 +2672,8 @@ struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
> > INIT_LIST_HEAD(&rdev->list);
> > BLOCKING_INIT_NOTIFIER_HEAD(&rdev->notifier);
> >
> > - /* preform any regulator specific init */
> > - if (init_data->regulator_init) {
> > - ret = init_data->regulator_init(rdev->reg_data);
> > - if (ret < 0)
> > - goto clean;
> > - }
> > + /* find device_node and attach it */
> > + rdev->dev.of_node = of_find_node_by_name(NULL, regulator_desc->name);
> >
> > /* register with sysfs */
> > rdev->dev.class = ®ulator_class;
> > @@ -2693,6 +2686,20 @@ struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
> > goto clean;
> > }
> >
> > + if (!init_data) {
> > + /* try to get init_data from device tree */
> > + init_data = of_get_regulator_init_data(&rdev->dev);
> > + if (!init_data)
> > + return ERR_PTR(-EINVAL);
> > + }
> > +
> > + /* preform any regulator specific init */
> > + if (init_data->regulator_init) {
> > + ret = init_data->regulator_init(rdev->reg_data);
> > + if (ret < 0)
> > + goto clean;
> > + }
> > +
> > dev_set_drvdata(&rdev->dev, rdev);
> >
> > /* set regulator constraints */
> > @@ -2719,7 +2726,7 @@ struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
> > node = of_get_regulator(dev, supply);
> > if (node)
> > list_for_each_entry(r, ®ulator_list, list)
> > - if (node == r->dev.parent->of_node)
> > + if (node == r->dev.of_node)
> > goto found;
> > }
> >
> > ------->8---
> >
> > And my dts file looks like something below.
> >
> > ecspi@...10000 { /* ECSPI1 */
> > fsl,spi-num-chipselects = <2>;
> > cs-gpios = <&gpio3 24 0>, /* GPIO4_24 */
> > <&gpio3 25 0>; /* GPIO4_25 */
> > status = "okay";
> >
> > pmic: mc13892@0 {
> > #address-cells = <1>;
> > #size-cells = <0>;
> > compatible = "fsl,mc13892";
> > spi-max-frequency = <6000000>;
> > reg = <0>;
> > mc13xxx-irq-gpios = <&gpio0 8 0>; /* GPIO1_8 */
> >
> > regulators {
> > sw1reg: mc13892_sw1 {
> > regulator-min-uV = <600000>;
> > regulator-max-uV = <1375000>;
> > regulator-change-voltage;
> > regulator-boot-on;
> > regulator-always-on;
> > };
> >
> > sw2reg: mc13892_sw2 {
> > regulator-min-uV = <900000>;
> > regulator-max-uV = <1850000>;
> > regulator-change-voltage;
> > regulator-boot-on;
> > regulator-always-on;
> > };
> >
> > ......
> > };
>
> To follow up from my earlier comment, this .dts structure looks fine
> and reasonable to me, and it would also be fine for the mc13892 driver
> to use for_each_child_of_node() to find all the children of the
> regulators node. Even finding the 'regulators' node by name from the
> mc13892 driver is perfectly fine provided for_each_child_of_node is
> used to find it. All of this is okay because it is under the umbrella
> of the "fsl,mc13892" binding.
>
For mc13892 regulator example, there are 3 levels 'struct dev'.
1. drivers/mfd/mc13xxx-core.c
The "fsl,mc13892" binding is used in this mfd driver to get
mc13xxx-core device probed. And this mfd driver will in turn
call mfd_add_devices() to add the second level device below.
2. drivers/regulator/mc13892-regulator.c
As this device is created by mfd_add_devices() above, there is no
device_node attached to its of_node, though we would hope that node
'regulators' is attached there. And the driver will call
regulator_register() to have each regulator device created and
registered in regulator core below.
3. drivers/regulator/core.c
regulator_register() called above will create device (rdev->dev)
for each regulator.
I am thinking about hiding the device_node discovering for each
regulator from the second level (regulator driver) and make it
internal to the third level (regulator core), as it seems to me
that regulator driver does not need to necessarily know about this.
If we can attach the device_node of 'regulators' node to dev->of_node
when calling regulator_register(regulator_desc, dev, ...) from
regulator driver, the regulator core will be able to find all nodes under
'regulators' using for_each_child_of_node(dev->of_node, child).
Then the question would be how we attach the device_node of 'regulators'
to dev->of_node where 'dev' is the second level device above. I somehow
hesitate to hack this into mfd_add_devices(), so I would like to add
compatible string "fsl,mc13892-regulators" to node 'regulators' and
find the node using of_find_compatible_node(dev->parent, NULL,
"fsl,mc13892-regulators").
I'm not sure this is exactly same as what your comment suggests above.
So please let me know if it's appropriate.
--
Regards,
Shawn
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