On Tue, Mar 21, 2017 at 10:54 PM, Alison Schofield <amsfield22@xxxxxxxxx> wrote:
> On Mon, Mar 20, 2017 at 01:09:21PM +0530, Gargi Sharma wrote:
>> The IIO subsystem is redefining iio_dev->mlock to be used by
>> the IIO core only for protecting device operating mode changes.
>> ie. Changes between INDIO_DIRECT_MODE, INDIO_BUFFER_* modes.
>>
>> In this driver, mlock was being used to protect hardware state
>> changes. Replace it with buf_lock in the devices global data.
>>
>> As buf_lock already protects operations in ade7754_write_frequency,
>> there isn't a need to acquire the lock inside ade7754_spi_write_reg_8
>> when writing to the register.
>
> Hi Gargi,
>
> Looks like something went wrong in your patch below. It doesn't do what
> you say it'll do...Instead of removing the lock from _write_reg_8()
> it inserts a bunch of code. Anyway, it seems that w_rite_reg_8() is used
> in multiple places, so removing that lock doesn't appear to be an
> option.
>
> See below...
>
> alisons
>
>>
>> Signed-off-by: Gargi Sharma <gs051095@xxxxxxxxx>
>> ---
>> drivers/staging/iio/meter/ade7754.c | 13 +++++++++++--
>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/iio/meter/ade7754.c b/drivers/staging/iio/meter/ade7754.c
>> index 024463a..eb03469 100644
>> --- a/drivers/staging/iio/meter/ade7754.c
>> +++ b/drivers/staging/iio/meter/ade7754.c
>> @@ -29,6 +29,15 @@ static int ade7754_spi_write_reg_8(struct device *dev, u8 reg_address, u8 val)
>> struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>> struct ade7754_state *st = iio_priv(indio_dev);
>>
>> + if (reg_address == ADE7754_WAVMODE) {
>> + st->tx[0] = ADE7754_WRITE_REG(reg_address);
>> + st->tx[1] = val;
>> +
>> + ret = spi_write(st->us, st->tx, 2);
>> +
>> + return ret;
>> + }
>> +
> What's this?
When the function ade_spi_write_reg_8() is called inside
ade7754_write_frequency(), we are writing to this( ADE7754_WAVMODE)
register. When writing to this register we don't need to hold the
buf_lock since ade7754_write_frequency() already takes care of that.
>
>> mutex_lock(&st->buf_lock);
>> st->tx[0] = ADE7754_WRITE_REG(reg_address);
>> st->tx[1] = val;
>> @@ -430,7 +439,7 @@ static ssize_t ade7754_write_frequency(struct device *dev,
>> if (!val)
>> return -EINVAL;
>>
>> - mutex_lock(&indio_dev->mlock);
>> + mutex_lock(&st->buf_lock);
>>
>> t = 26000 / val;
>> if (t > 0)
>> @@ -451,7 +460,7 @@ static ssize_t ade7754_write_frequency(struct device *dev,
>> ret = ade7754_spi_write_reg_8(dev, ADE7754_WAVMODE, reg);
>>
>> out:
>> - mutex_unlock(&indio_dev->mlock);
>> + mutex_unlock(&st->buf_lock);
>>
>> return ret ? ret : len;
>> }
The buf_lock inside ade7754_write_frequency() takes into account that
when using the function ade7754_spi_write_reg_8, lock is already held
and locking is no longer required inside the ade7754_spi_write_reg_8()
function.
Let me know if this sounds okay, I can perhaps edit the commit log to
make this clearer.
Thanks,
Gargi
>> --
>> 2.7.4
>>
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