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Message-ID: <5201F42B.5040308@nvidia.com>
Date: Wed, 7 Aug 2013 15:15:55 +0800
From: Wei Ni <wni@...dia.com>
To: Guenter Roeck <linux@...ck-us.net>
CC: "khali@...ux-fr.org" <khali@...ux-fr.org>,
"swarren@...dotorg.org" <swarren@...dotorg.org>,
Matthew Longnecker <MLongnecker@...dia.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 1/2] hwmon: (lm90) Add power control
On 08/07/2013 03:03 PM, Guenter Roeck wrote:
> On 08/06/2013 11:52 PM, Wei Ni wrote:
>> The device lm90 can be controlled by the vdd rail.
>> Adding the power control support to power on/off the vdd rail.
>> And make sure that power is enabled before accessing the device.
>>
>> Signed-off-by: Wei Ni <wni@...dia.com>
>> ---
>> drivers/hwmon/lm90.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 52 insertions(+)
>>
>> diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
>> index cdff742..eeb0115 100644
>> --- a/drivers/hwmon/lm90.c
>> +++ b/drivers/hwmon/lm90.c
>> @@ -89,6 +89,8 @@
>> #include <linux/err.h>
>> #include <linux/mutex.h>
>> #include <linux/sysfs.h>
>> +#include <linux/delay.h>
>> +#include <linux/regulator/consumer.h>
>>
>> /*
>> * Addresses to scan
>> @@ -179,6 +181,8 @@ enum chips { lm90, adm1032, lm99, lm86, max6657, max6659, adt7461, max6680,
>> #define LM90_HAVE_TEMP3 (1 << 6) /* 3rd temperature sensor */
>> #define LM90_HAVE_BROKEN_ALERT (1 << 7) /* Broken alert */
>>
>> +#define POWER_ON_DELAY 20 /*ms*/
>> +
>> /*
>> * Driver data (common to all clients)
>> */
>> @@ -302,6 +306,7 @@ static const struct lm90_params lm90_params[] = {
>> struct lm90_data {
>> struct device *hwmon_dev;
>> struct mutex update_lock;
>> + struct regulator *lm90_reg;
>> char valid; /* zero until following fields are valid */
>> unsigned long last_updated; /* in jiffies */
>> int kind;
>> @@ -1391,6 +1396,48 @@ static void lm90_init_client(struct i2c_client *client)
>> i2c_smbus_write_byte_data(client, LM90_REG_W_CONFIG1, config);
>> }
>>
>> +static int lm90_power_control(struct i2c_client *client, bool is_enable)
>> +{
>> + struct lm90_data *data = i2c_get_clientdata(client);
>> + int ret;
>> +
>> + mutex_lock(&data->update_lock);
>> +
>> + if (!data->lm90_reg) {
>> + data->lm90_reg = regulator_get(&client->dev, "vdd");
>> + if (IS_ERR_OR_NULL(data->lm90_reg)) {
>> + if (PTR_ERR(data->lm90_reg) == -ENODEV)
>> + dev_info(&client->dev,
>> + "No regulator found for vdd. Assuming vdd is always powered.");
>> + else
>> + dev_warn(&client->dev,
>> + "Error [%ld] in getting the regulator handle for vdd.\n",
>> + PTR_ERR(data->lm90_reg));
>> + data->lm90_reg = NULL;
>> + mutex_unlock(&data->update_lock);
>> + return -ENODEV;
>
> I don't think it is acceptable to have the driver fail on pretty much all PCs.
Yes, you are right, I didn't consider it carefully, I will fix it.
I think it's better to move these codes to the probe() directly.
>
> Also, I dislike that - even if the calling code doesn't fail - the above message would be displayed on unload as well.
>
> In general, the 'unload' flag seems unnecessary. You could just call
>
> if (data->lm90_reg)
> regulator_disable();
>
> in the remove function. In addition to that, shouldn't you call regulator_put() on exit ?
Oh, sorry, I miss the regulator_put(), I will fix it.
> Also, I am missing error handling in the probe function; if something else fails,
> the regulator is neither disabled nor released.
It looks this patch have many problems, I will fix them.
Thanks for your comments.
>
> Guenter
>
>> + }
>> + }
>> + if (is_enable) {
>> + ret = regulator_enable(data->lm90_reg);
>> + msleep(POWER_ON_DELAY);
>> + } else {
>> + ret = regulator_disable(data->lm90_reg);
>> + }
>> +
>> + if (ret < 0)
>> + dev_err(&client->dev,
>> + "Error in %s rail vdd, error %d\n",
>> + (is_enable) ? "enabling" : "disabling", ret);
>> + else
>> + dev_info(&client->dev, "success in %s rail vdd\n",
>> + (is_enable) ? "enabling" : "disabling");
>> +
>> + mutex_unlock(&data->update_lock);
>> +
>> + return ret;
>> +}
>> +
>> static int lm90_probe(struct i2c_client *client,
>> const struct i2c_device_id *id)
>> {
>> @@ -1406,6 +1453,10 @@ static int lm90_probe(struct i2c_client *client,
>> i2c_set_clientdata(client, data);
>> mutex_init(&data->update_lock);
>>
>> + err = lm90_power_control(client, true);
>> + if (err < 0)
>> + return err;
>> +
>> /* Set the device type */
>> data->kind = id->driver_data;
>> if (data->kind == adm1032) {
>> @@ -1483,6 +1534,7 @@ static int lm90_remove(struct i2c_client *client)
>> hwmon_device_unregister(data->hwmon_dev);
>> lm90_remove_files(client, data);
>> lm90_restore_conf(client, data);
>> + lm90_power_control(client, false);
>>
>> return 0;
>> }
>>
>
--
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