Hi Paul,
On 29/12/15 20:13, Paul Kocialkowski wrote:
Hi Milo,
Le mardi 29 décembre 2015 à 09:45 +0900, Milo Kim a écrit :
Hi Paul,
On 29/12/15 07:49, Paul Kocialkowski wrote:
Hi Milo, thanks for the review,
Le lundi 28 décembre 2015 à 09:56 +0900, Milo Kim a écrit :
Hi Paul,
On 23/12/15 20:56, Mark Brown wrote:
On Wed, Dec 23, 2015 at 11:58:37AM +0100, Paul Kocialkowski wrote:
+ gpio = lp->pdata->enable_gpio;
+ if (!gpio_is_valid(gpio))
+ return 0;
+
+ /* Always set enable GPIO high. */
+ ret = devm_gpio_request_one(lp->dev, gpio, GPIOF_OUT_INIT_HIGH, "LP872X EN");
+ if (ret) {
+ dev_err(lp->dev, "gpio request err: %d\n", ret);
+ return ret;
+ }
This isn't really adding support for the enable GPIO as the changelog
suggests, it's requesting but not managing the GPIO. Since there is
core support for manging enable GPIOs this seems especially silly,
please tell the core about the GPIO and then it will work at runtime
too.
With reference to my previous mail, external GPIOs for LDO3 and BUCK2 in
LP8725 can be specified through regulator_config.ena_gpio. BUCK2 only
can be controlled by external pin when CONFIG pin is grounded.
Please see the description at page 5 of the datasheet.
http://www.ti.com/lit/ds/symlink/lp8725.pdf
After reading the datasheets thoroughly, it seems to me that for the
lp8720, the EN pin is used to enable the regulators output, which is a
good fit for the core regulator GPIO framework, as there is no reason to
keep it on when no regulator is in use. The serial interface is already
available when EN=0 and regulators can be configured in that state. The
lp8725 seems seems to behave the same when CONFIG=0 (the datasheet
clearly states: "CONFIG=0: EN=1 turns on outputs or standby mode if
EN=0"). On the other hand, it is indeed used as a power-on pin when
CONFIG=1.
I think it's different use case. LP8720/5 are designed for system PMU,
so some regulators are enabled by default after the device is on. EN pin
is used for turning on/off the chip. This pin does not control regulator
outputs directly. It's separate functional block in the silicon.
Well, I really don't understand why the EN pin would turn on/off the
chip. All it does it enable the regulators outputs (by entering IDLE
mode), the serial block is already available in STANDBY state.
If we want some regulators enabled at boot, the best thing to do seems
to be to request the GPIO with the GPIOF_INIT_HIGH flag, as done in e.g.
the max8952 regulator driver:
if (pdata->reg_data->constraints.boot_on)
config.ena_gpio_flags |= GPIOF_OUT_INIT_HIGH;
According to MAX8952 datasheet, output regulator is enabled/disabled
using EN pin, so ena_gpio is used correctly.
However, LP8720/5 regulators are enabled/disabled through I2C command.
Only few regulators of LP8725 can be on/off by separate external pins.
(B2_EN and LDO3_EN)
Please note that EN pin in LP8720/5 is not the control pin for
enabling/disabling regulators.
Best regards,
Milo
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