From: Tomasz Figa <tfiga@chromium.org>
To: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: linux-i2c <linux-i2c@vger.kernel.org>,
Wolfram Sang <wsa@the-dreams.de>,
"Rafael J. Wysocki" <rafael@kernel.org>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Mani, Rajmohan" <rajmohan.mani@intel.com>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Bingbu Cao <bingbu.cao@intel.com>,
Chiranjeevi Rapolu <chiranjeevi.rapolu@intel.com>,
Hyungwoo Yang <hyungwoo.yang@intel.com>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: Re: [PATCH v8 6/6] at24: Support probing while off
Date: Tue, 6 Oct 2020 13:23:35 +0200 [thread overview]
Message-ID: <CAAFQd5Br6DePtvAukfjyPc9JEveZzg6ymSv2B+sfN0eOWLvDNw@mail.gmail.com> (raw)
In-Reply-To: <CAAFQd5DqYHckYA4LSkt5UN35HuOLC=rJhPFHbGu8p-B2vSTrqg@mail.gmail.com>
On Tue, Oct 6, 2020 at 1:20 PM Tomasz Figa <tfiga@chromium.org> wrote:
>
> Hi Sakari,
>
> On Thu, Sep 3, 2020 at 10:15 AM Sakari Ailus
> <sakari.ailus@linux.intel.com> wrote:
> >
> > In certain use cases (where the chip is part of a camera module, and the
> > camera module is wired together with a camera privacy LED), powering on
> > the device during probe is undesirable. Add support for the at24 to
> > execute probe while being powered off. For this to happen, a hint in form
> > of a device property is required from the firmware.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > ---
> > drivers/misc/eeprom/at24.c | 43 +++++++++++++++++++++++---------------
> > 1 file changed, 26 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > index 8f5de5f10bbea..2d24e33788d7d 100644
> > --- a/drivers/misc/eeprom/at24.c
> > +++ b/drivers/misc/eeprom/at24.c
> > @@ -595,6 +595,7 @@ static int at24_probe(struct i2c_client *client)
> > bool i2c_fn_i2c, i2c_fn_block;
> > unsigned int i, num_addresses;
> > struct at24_data *at24;
> > + bool low_power;
> > struct regmap *regmap;
> > bool writable;
> > u8 test_byte;
> > @@ -733,25 +734,30 @@ static int at24_probe(struct i2c_client *client)
> >
> > i2c_set_clientdata(client, at24);
> >
> > - err = regulator_enable(at24->vcc_reg);
> > - if (err) {
> > - dev_err(dev, "Failed to enable vcc regulator\n");
> > - return err;
> > - }
> > + low_power = acpi_dev_state_low_power(&client->dev);
> > + if (!low_power) {
> > + err = regulator_enable(at24->vcc_reg);
> > + if (err) {
> > + dev_err(dev, "Failed to enable vcc regulator\n");
> > + return err;
> > + }
> >
> > - /* enable runtime pm */
> > - pm_runtime_set_active(dev);
> > + pm_runtime_set_active(dev);
> > + }
> > pm_runtime_enable(dev);
> >
>
> What's the guarantee that at this point the runtime PM wouldn't
> suspend the device? Notice that the nvmem device is already exposed to
> the userspace, which could trigger pm runtime gets and puts (and thus
> idles as well).
>
> Best regards,
> Tomasz
>
> > /*
> > - * Perform a one-byte test read to verify that the
> > - * chip is functional.
> > + * Perform a one-byte test read to verify that the chip is functional,
> > + * unless powering on the device is to be avoided during probe (i.e.
> > + * it's powered off right now).
> > */
> > - err = at24_read(at24, 0, &test_byte, 1);
Actually never mind. Someone pointed out to me that at24_read() calls
pm_runtime_get_sync() internally, so we should be fine. Sorry, for the
noise.
Best regards,
Tomasz
> > - if (err) {
> > - pm_runtime_disable(dev);
> > - regulator_disable(at24->vcc_reg);
> > - return -ENODEV;
> > + if (!low_power) {
> > + err = at24_read(at24, 0, &test_byte, 1);
> > + if (err) {
> > + pm_runtime_disable(dev);
> > + regulator_disable(at24->vcc_reg);
> > + return -ENODEV;
> > + }
> > }
> >
> > pm_runtime_idle(dev);
> > @@ -771,9 +777,11 @@ static int at24_remove(struct i2c_client *client)
> > struct at24_data *at24 = i2c_get_clientdata(client);
> >
> > pm_runtime_disable(&client->dev);
> > - if (!pm_runtime_status_suspended(&client->dev))
> > - regulator_disable(at24->vcc_reg);
> > - pm_runtime_set_suspended(&client->dev);
> > + if (!acpi_dev_state_low_power(&client->dev)) {
> > + if (!pm_runtime_status_suspended(&client->dev))
> > + regulator_disable(at24->vcc_reg);
> > + pm_runtime_set_suspended(&client->dev);
> > + }
> >
> > return 0;
> > }
> > @@ -810,6 +818,7 @@ static struct i2c_driver at24_driver = {
> > .probe_new = at24_probe,
> > .remove = at24_remove,
> > .id_table = at24_ids,
> > + .flags = I2C_DRV_FL_ALLOW_LOW_POWER_PROBE,
> > };
> >
> > static int __init at24_init(void)
> > --
> > 2.20.1
> >
next prev parent reply other threads:[~2020-10-06 11:23 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 8:15 [PATCH v8 0/6] Support running driver's probe for a device powered off Sakari Ailus
2020-09-03 8:15 ` [PATCH v8 1/6] i2c: Allow an ACPI driver to manage the device's power state during probe Sakari Ailus
2020-09-03 8:15 ` [PATCH v8 2/6] Documentation: ACPI: Document i2c-allow-low-power-probe _DSD property Sakari Ailus
2020-09-03 8:15 ` [PATCH v8 3/6] ACPI: Add a convenience function to tell a device is in low power state Sakari Ailus
[not found] ` <0c2d4728-6e32-ef93-8961-381fe36cfdaa@linux.intel.com>
2020-09-11 13:01 ` Sakari Ailus
2020-09-03 8:15 ` [PATCH v8 4/6] ov5670: Support probe whilst the device is in a " Sakari Ailus
2020-09-03 8:15 ` [PATCH v8 5/6] media: i2c: imx319: Support probe while the device is off Sakari Ailus
2020-09-03 8:15 ` [PATCH v8 6/6] at24: Support probing while off Sakari Ailus
2020-09-09 9:35 ` Bartosz Golaszewski
2020-09-09 11:11 ` Wolfram Sang
2020-09-09 11:56 ` Bartosz Golaszewski
2020-09-09 12:16 ` Sakari Ailus
2020-09-11 12:11 ` Sakari Ailus
2020-10-06 11:20 ` Tomasz Figa
2020-10-06 11:23 ` Tomasz Figa [this message]
2020-09-11 12:49 ` [PATCH v8 0/6] Support running driver's probe for a device powered off Luca Ceresoli
2020-09-11 13:01 ` Sakari Ailus
2020-09-14 7:58 ` Luca Ceresoli
[not found] ` <20200914094727.GM26842@paasikivi.fi.intel.com>
2020-09-14 16:49 ` Luca Ceresoli
2020-09-23 11:08 ` Sakari Ailus
2020-09-23 15:37 ` Luca Ceresoli
2020-09-26 12:38 ` Tomasz Figa
2020-09-27 19:39 ` Wolfram Sang
2020-09-27 19:44 ` Tomasz Figa
2020-09-28 14:17 ` Rafael J. Wysocki
2020-09-28 16:49 ` Tomasz Figa
2020-09-28 20:49 ` Sakari Ailus
2020-09-26 12:46 ` Tomasz Figa
2021-01-28 23:27 ` [PATCH v9 1/7] ACPI: scan: Obtain device's desired enumeration power state Sakari Ailus
[not found] ` <CAJZ5v0hdG1W0D5E6GbrTDiAjMyC0mSgb3Z2WEBy3hhb4iJhDNw@mail.gmail.com>
2021-01-29 16:45 ` Sakari Ailus
2021-01-29 16:57 ` Rafael J. Wysocki
2021-01-29 21:22 ` Sakari Ailus
2021-02-01 11:44 ` Rafael J. Wysocki
2021-01-28 23:27 ` [PATCH v9 2/7] i2c: Allow an ACPI driver to manage the device's power state during probe Sakari Ailus
2021-01-28 23:27 ` [PATCH v9 3/7] Documentation: ACPI: Document _PRE object usage for enum power state Sakari Ailus
2021-01-28 23:27 ` [PATCH v9 4/7] ACPI: Add a convenience function to tell a device is in low " Sakari Ailus
2021-01-28 23:27 ` [PATCH v9 5/7] ov5670: Support probe whilst the device is in a " Sakari Ailus
2021-01-28 23:27 ` [PATCH v9 6/7] media: i2c: imx319: Support probe while the device is off Sakari Ailus
2021-01-29 2:58 ` Bingbu Cao
2021-01-28 23:27 ` [PATCH v9 7/7] at24: Support probing while off Sakari Ailus
[not found] ` <CAMpxmJVTPgvxOVdTkmt4VjUnGabNBKauKF_DKtnnkV6O0QYTWA@mail.gmail.com>
[not found] ` <20210129121955.GH32460@paasikivi.fi.intel.com>
2021-02-01 8:57 ` Bartosz Golaszewski
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