On Tue, Oct 22, 2019 at 1:53 AM Bartosz Golaszewski
<bgolaszewski@xxxxxxxxxxxx> wrote:
>
> pt., 18 paź 2019 o 10:26 Bibby Hsieh <bibby.hsieh@xxxxxxxxxxxx> napisał(a):
> >
> > Although in the most platforms, the power of eeprom and i2c
> > are alway on, some platforms disable the eeprom and i2c power
> > in order to meet low power request.
> > This patch add the pm_runtime ops to control power to support
> > all platforms.
> >
> > Changes since v3:
> > - remove redundant calling function
> > - change SIMPLE_DEV_PM_OPS to SET_RUNTIME_PM_OPS
> > - change supply name
> >
> > Changes since v2:
> > - rebase onto v5.4-rc1
> > - pm_runtime_disable and regulator_bulk_disable at
> > err return in probe function
> >
> > Changes since v1:
> > - remove redundant code
> > - fixup coding style
> >
> > Signed-off-by: Bibby Hsieh <bibby.hsieh@xxxxxxxxxxxx>
> > ---
> > drivers/misc/eeprom/at24.c | 64 ++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 64 insertions(+)
> >
> > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > index 2cccd82a3106..68ced4f25916 100644
> > --- a/drivers/misc/eeprom/at24.c
> > +++ b/drivers/misc/eeprom/at24.c
> > @@ -22,6 +22,7 @@
> > #include <linux/nvmem-provider.h>
> > #include <linux/regmap.h>
> > #include <linux/pm_runtime.h>
> > +#include <linux/regulator/consumer.h>
> > #include <linux/gpio/consumer.h>
> >
> > /* Address pointer is 16 bit. */
> > @@ -67,6 +68,12 @@
> > * which won't work on pure SMBus systems.
> > */
> >
> > +static const char * const at24_supply_names[] = {
> > + "vcc", "i2c",
> > +};
> > +
> > +#define AT24_NUM_SUPPLIES ARRAY_SIZE(at24_supply_names)
> > +
> > struct at24_client {
> > struct i2c_client *client;
> > struct regmap *regmap;
> > @@ -91,6 +98,8 @@ struct at24_data {
> >
> > struct gpio_desc *wp_gpio;
> >
> > + bool has_supplies;
> > + struct regulator_bulk_data supplies[AT24_NUM_SUPPLIES];
> > /*
> > * Some chips tie up multiple I2C addresses; dummy devices reserve
> > * them for us, and we'll use them with SMBus calls.
> > @@ -662,6 +671,17 @@ static int at24_probe(struct i2c_client *client)
> > at24->client[0].client = client;
> > at24->client[0].regmap = regmap;
> >
> > + regulator_bulk_set_supply_names(at24->supplies,
> > + at24_supply_names, AT24_NUM_SUPPLIES);
> > + err = devm_regulator_bulk_get(&at24->client[0].client->dev,
> > + AT24_NUM_SUPPLIES, at24->supplies);
> > + if (err == -ENODEV)
> > + at24->has_supplies = NULL;
>
> I just gave this a spin and noticed that this will never happen - the
> regulator core will use a dummy regulator if none is defined in DT.
> The only way for this to make sense would be to use
> regulator_get_optional() for each supply separately. But actually I
> think we should just leave it this way and remove this if. In the end:
> this chip needs some power supply, so dummy regulator makes sense.
Thanks for testing. I'd still like to make sure what happens on non-DT
platforms.
I can see that the core returns the dummy regulator if
have_full_constraints() [1]. That is always true for DT systems, but
for others it's false by default, unless someone explicitly calls
regulator_has_full_constraints() [2].
[1] https://elixir.bootlin.com/linux/v5.4-rc2/source/drivers/regulator/core.c#L1787
[2] https://elixir.bootlin.com/linux/v5.4-rc2/source/drivers/regulator/core.c#L120
Best regards,
Tomasz
