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[209.85.221.45]) by smtp.gmail.com with ESMTPSA id h22sm1942663ejc.80.2020.10.06.04.23.48 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 Oct 2020 04:23:49 -0700 (PDT) Received: by mail-wr1-f45.google.com with SMTP id t10so13029471wrv.1 for ; Tue, 06 Oct 2020 04:23:48 -0700 (PDT) X-Received: by 2002:adf:df8e:: with SMTP id z14mr4285634wrl.32.1601983428264; Tue, 06 Oct 2020 04:23:48 -0700 (PDT) MIME-Version: 1.0 References: <20200903081550.6012-1-sakari.ailus@linux.intel.com> <20200903081550.6012-7-sakari.ailus@linux.intel.com> In-Reply-To: From: Tomasz Figa Date: Tue, 6 Oct 2020 13:23:35 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v8 6/6] at24: Support probing while off To: Sakari Ailus Cc: linux-i2c , Wolfram Sang , "Rafael J. Wysocki" , ACPI Devel Maling List , Linux Kernel Mailing List , Greg Kroah-Hartman , "Mani, Rajmohan" , Bartosz Golaszewski , Bingbu Cao , Chiranjeevi Rapolu , Hyungwoo Yang , Linux Media Mailing List , Sergey Senozhatsky Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Tue, Oct 6, 2020 at 1:20 PM Tomasz Figa wrote: > > Hi Sakari, > > On Thu, Sep 3, 2020 at 10:15 AM Sakari Ailus > 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 > > --- > > 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 > >