Hi Sakari & Tomas, Are you ok with the current revision, let me know if any changes are needed. --- ^Divagar >-----Original Message----- >From: sakari.ailus@xxxxxx [mailto:sakari.ailus@xxxxxx] >Sent: Wednesday, September 20, 2017 3:02 PM >To: Tomasz Figa <tfiga@xxxxxxxxxxxx> >Cc: Mani, Rajmohan <rajmohan.mani@xxxxxxxxx>; Mohandass, Divagar ><divagar.mohandass@xxxxxxxxx>; robh+dt@xxxxxxxxxx; >mark.rutland@xxxxxxx; wsa@xxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; >linux-i2c@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; >mika.westerberg@xxxxxxxxxxxxxxx >Subject: Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support > >Hi Tomasz, > >On Wed, Sep 20, 2017 at 05:59:18PM +0900, Tomasz Figa wrote: >> On Wed, Sep 20, 2017 at 5:45 PM, sakari.ailus@xxxxxx >> <sakari.ailus@xxxxxx> wrote: >> > Hi Tomasz, >> > >> > On Wed, Sep 20, 2017 at 12:56:09PM +0900, Tomasz Figa wrote: >> >> Thanks Raj. >> >> >> >> Let me post my comments inline. >> >> >> >> On Wed, Sep 20, 2017 at 12:52 PM, Mani, Rajmohan >> >> <rajmohan.mani@xxxxxxxxx> wrote: >> >> > Adding Tomasz... >> >> > >> >> >> -----Original Message----- >> >> >> From: Mohandass, Divagar >> >> >> Sent: Monday, September 04, 2017 3:29 AM >> >> >> To: robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; wsa@the- >dreams.de; >> >> >> sakari.ailus@xxxxxx >> >> >> Cc: devicetree@xxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; >> >> >> linux- kernel@xxxxxxxxxxxxxxx; Mani, Rajmohan >> >> >> <rajmohan.mani@xxxxxxxxx>; Mohandass, Divagar >> >> >> <divagar.mohandass@xxxxxxxxx> >> >> >> Subject: [PATCH v6 3/3] eeprom: at24: enable runtime pm support >> >> >> >> >> >> Currently the device is kept in D0, there is an opportunity to >> >> >> save power by enabling runtime pm. >> >> >> >> >> >> Device can be daisy chained from PMIC and we can't rely on I2C >> >> >> core for auto resume/suspend. Driver will decide when to >resume/suspend. >> >> >> >> >> >> Signed-off-by: Divagar Mohandass <divagar.mohandass@xxxxxxxxx> >> >> >> --- >> >> >> drivers/misc/eeprom/at24.c | 38 >> >> >> ++++++++++++++++++++++++++++++++++++++ >> >> >> 1 file changed, 38 insertions(+) >> >> >> >> >> >> diff --git a/drivers/misc/eeprom/at24.c >> >> >> b/drivers/misc/eeprom/at24.c index 2199c42..d718a7a 100644 >> >> >> --- a/drivers/misc/eeprom/at24.c >> >> >> +++ b/drivers/misc/eeprom/at24.c >> >> >> @@ -24,6 +24,7 @@ >> >> >> #include <linux/i2c.h> >> >> >> #include <linux/nvmem-provider.h> #include >> >> >> <linux/platform_data/at24.h> >> >> >> +#include <linux/pm_runtime.h> >> >> >> >> >> >> /* >> >> >> * I2C EEPROMs from most vendors are inexpensive and mostly >> >> >> interchangeable. >> >> >> @@ -501,11 +502,21 @@ static ssize_t >> >> >> at24_eeprom_write_i2c(struct at24_data *at24, const char *buf, >> >> >> static int at24_read(void *priv, unsigned int off, void *val, size_t >count) { >> >> >> struct at24_data *at24 = priv; >> >> >> + struct i2c_client *client; >> >> >> char *buf = val; >> >> >> + int ret; >> >> >> >> >> >> if (unlikely(!count)) >> >> >> return count; >> >> >> >> >> >> + client = at24_translate_offset(at24, &off); >> >> >> + >> >> >> + ret = pm_runtime_get_sync(&client->dev); >> >> >> + if (ret < 0) { >> >> >> + pm_runtime_put_noidle(&client->dev); >> >> >> + return ret; >> >> >> + } >> >> >> + >> >> >> /* >> >> >> * Read data from chip, protecting against concurrent updates >> >> >> * from this host, but not from other I2C masters. >> >> >> @@ -518,6 +529,7 @@ static int at24_read(void *priv, unsigned >> >> >> int off, void *val, size_t count) >> >> >> status = at24->read_func(at24, buf, off, count); >> >> >> if (status < 0) { >> >> >> mutex_unlock(&at24->lock); >> >> >> + pm_runtime_put(&client->dev); >> >> >> return status; >> >> >> } >> >> >> buf += status; >> >> >> @@ -527,17 +539,29 @@ static int at24_read(void *priv, unsigned >> >> >> int off, void *val, size_t count) >> >> >> >> >> >> mutex_unlock(&at24->lock); >> >> >> >> >> >> + pm_runtime_put(&client->dev); >> >> >> + >> >> >> return 0; >> >> >> } >> >> >> >> >> >> static int at24_write(void *priv, unsigned int off, void *val, size_t >count) { >> >> >> struct at24_data *at24 = priv; >> >> >> + struct i2c_client *client; >> >> >> char *buf = val; >> >> >> + int ret; >> >> >> >> >> >> if (unlikely(!count)) >> >> >> return -EINVAL; >> >> >> >> >> >> + client = at24_translate_offset(at24, &off); >> >> >> + >> >> >> + ret = pm_runtime_get_sync(&client->dev); >> >> >> + if (ret < 0) { >> >> >> + pm_runtime_put_noidle(&client->dev); >> >> >> + return ret; >> >> >> + } >> >> >> + >> >> >> /* >> >> >> * Write data to chip, protecting against concurrent updates >> >> >> * from this host, but not from other I2C masters. >> >> >> @@ -550,6 +574,7 @@ static int at24_write(void *priv, unsigned >> >> >> int off, void *val, size_t count) >> >> >> status = at24->write_func(at24, buf, off, count); >> >> >> if (status < 0) { >> >> >> mutex_unlock(&at24->lock); >> >> >> + pm_runtime_put(&client->dev); >> >> >> return status; >> >> >> } >> >> >> buf += status; >> >> >> @@ -559,6 +584,8 @@ static int at24_write(void *priv, unsigned >> >> >> int off, void *val, size_t count) >> >> >> >> >> >> mutex_unlock(&at24->lock); >> >> >> >> >> >> + pm_runtime_put(&client->dev); >> >> >> + >> >> >> return 0; >> >> >> } >> >> >> >> >> >> @@ -743,11 +770,17 @@ static int at24_probe(struct i2c_client >> >> >> *client, const struct i2c_device_id *id) >> >> >> >> >> >> i2c_set_clientdata(client, at24); >> >> >> >> >> >> + /* enable runtime pm */ >> >> >> + pm_runtime_get_noresume(&client->dev); >> >> >> + pm_runtime_set_active(&client->dev); >> >> >> + pm_runtime_enable(&client->dev); >> >> >> >> Do we need this get_noresume/set_active dance? I remember it was >> >> for some reason needed for PCI devices, but I don't see why for I2C >> >> anything else than just pm_runtime_enable() would be necessary. >> > >> > You specifically do not need (all) this for PCI devices, but AFAIU >> > for I涎 >> > devices you do. The runtime PM status of a device is disabled by >> > default and the use count is zero, but on ACPI based systems the >> > device is still powered on. >> >> Okay, so _get_noresume() and _set_active() would do the thing for ACPI >> indeed, but not sure about other platforms. Perhaps _enable(), >> _get_sync() would be more general? > >What I ended up doing in e.g. the smiapp driver was to explicitly power the >device on first and then enable runtime PM. (See >drivers/media/i2c/smiapp/smiapp-core.c .) This approach works even if >CONFIG_PM is disabled, both on DT and ACPI. > >-- >Regards, > >Sakari Ailus >e-mail: sakari.ailus@xxxxxx ��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
