Hi Sakari,

Thanks for your time.
My comments below.

---
^Divagar

-----Original Message-----
From: Sakari Ailus [mailto:sakari.ailus@iki.fi]
Sent: Wednesday, August 30, 2017 1:24 PM
To: Mohandass, Divagar <redacted>
Cc: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-dreams.de;
devicetree@vger.kernel.org; linux-i2c@vger.kernel.org; linux-
kernel@vger.kernel.org; Mani, Rajmohan [off-list ref]
Subject: Re: [PATCH v3 3/3] eeprom: at24: enable runtime pm support

Hi Divagar,

Thanks for the update. A few more comments below.

On Wed, Aug 30, 2017 at 09:41:06AM +0530, Divagar Mohandass wrote:

quoted

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 <redacted>
---
 drivers/misc/eeprom/at24.c | 39
+++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 2199c42..a670814 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.

quoted

@@ -501,11 +502,22 @@ 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);
+		pm_runtime_put(&client->dev);

Two puts are too much here. How about dropping this one?

Ack
Will fix in next version.

quoted

+		return ret;
+	}
+
 	/*
 	 * Read data from chip, protecting against concurrent updates
 	 * from this host, but not from other I2C masters.

If an error happens between the two chunks, you'll need pm_runtime_put(),
too.

Ack

quoted

@@ -527,17 +539,30 @@ 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);
+		pm_runtime_put(&client->dev);

Same here.

Ack

quoted

+		return ret;
+	}
+
 	/*
 	 * Write data to chip, protecting against concurrent updates
 	 * from this host, but not from other I2C masters.

Ditto.

Ack

quoted

@@ -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;
 }

@@ -743,6 +770,15 @@ 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);
+	err = pm_runtime_set_active(&client->dev);
+	if (err < 0)
+		goto err_clients;
+
+	pm_runtime_enable(&client->dev);
+	pm_runtime_put(&client->dev);
+

You're just about to perform a read here. I believe you should move the last
put after that.

At the end of at24_read we are performing a pm_runtime_put, still we need this change ?

quoted

 	/*
 	 * Perform a one-byte test read to verify that the
 	 * chip is functional.

@@ -810,6 +846,9 @@ static int at24_remove(struct i2c_client *client)
 	for (i = 1; i < at24->num_addresses; i++)
 		i2c_unregister_device(at24->client[i]);

+	pm_runtime_disable(&client->dev);
+	pm_runtime_set_suspended(&client->dev);
+
 	return 0;
 }

--
Regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi