[PATCH v2] iio: mcp320x: Fix occasional incorrect readings

[PATCH v2] iio: mcp320x: Fix occasional incorrect readings

[Michael Welling]

Without the cacheline alignment, the readings will occasionally incorrectly
return 0.

Signed-off-by: Michael Welling <mwelling@ieee.org>
---

v2: Moved buffers to the end of the mcp320x struct per suggestion to keep
them on their own cacheline.

 drivers/iio/adc/mcp320x.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
index efbfd12..8d9c9b9 100644
--- a/drivers/iio/adc/mcp320x.c
+++ b/drivers/iio/adc/mcp320x.c
@@ -60,12 +60,12 @@ struct mcp320x {
 	struct spi_message msg;
 	struct spi_transfer transfer[2];
 
-	u8 tx_buf;
-	u8 rx_buf[2];
-
 	struct regulator *reg;
 	struct mutex lock;
 	const struct mcp320x_chip_info *chip_info;
+
+	u8 tx_buf ____cacheline_aligned;
+	u8 rx_buf[2];
 };
 
 static int mcp320x_channel_to_tx_data(int device_index,
-- 
1.7.9.5

Re: [PATCH v2] iio: mcp320x: Fix occasional incorrect readings

[Jonathan Cameron]

On 06/05/15 17:49, Michael Welling wrote:
> Without the cacheline alignment, the readings will occasionally incorrectly
> return 0.
> 
> Signed-off-by: Michael Welling <mwelling@ieee.org>
Applied to the fixes-togreg branch of iio.git.  Not sure
when I'll be able to push this out publicly as travelling
/ working nights and generally having a silly week.

J
> ---
> 
> v2: Moved buffers to the end of the mcp320x struct per suggestion to keep
> them on their own cacheline.
> 
>  drivers/iio/adc/mcp320x.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
> index efbfd12..8d9c9b9 100644
> --- a/drivers/iio/adc/mcp320x.c
> +++ b/drivers/iio/adc/mcp320x.c
> @@ -60,12 +60,12 @@ struct mcp320x {
>  	struct spi_message msg;
>  	struct spi_transfer transfer[2];
>  
> -	u8 tx_buf;
> -	u8 rx_buf[2];
> -
>  	struct regulator *reg;
>  	struct mutex lock;
>  	const struct mcp320x_chip_info *chip_info;
> +
> +	u8 tx_buf ____cacheline_aligned;
> +	u8 rx_buf[2];
>  };
>  
>  static int mcp320x_channel_to_tx_data(int device_index,
> 

Re: [PATCH v2] iio: mcp320x: Fix occasional incorrect readings

[Michael Welling]

On Thu, May 07, 2015 at 11:13:15AM +0100, Jonathan Cameron wrote:
> On 06/05/15 17:49, Michael Welling wrote:
> > Without the cacheline alignment, the readings will occasionally incorrectly
> > return 0.
> > 
> > Signed-off-by: Michael Welling <mwelling@ieee.org>
> Applied to the fixes-togreg branch of iio.git.  Not sure
> when I'll be able to push this out publicly as travelling
> / working nights and generally having a silly week.
> 
> J

Thanks.

Appearently code can be silly too:
https://lkml.org/lkml/2015/5/7/879

> > ---
> > 
> > v2: Moved buffers to the end of the mcp320x struct per suggestion to keep
> > them on their own cacheline.
> > 
> >  drivers/iio/adc/mcp320x.c |    6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
> > index efbfd12..8d9c9b9 100644
> > --- a/drivers/iio/adc/mcp320x.c
> > +++ b/drivers/iio/adc/mcp320x.c
> > @@ -60,12 +60,12 @@ struct mcp320x {
> >  	struct spi_message msg;
> >  	struct spi_transfer transfer[2];
> >  
> > -	u8 tx_buf;
> > -	u8 rx_buf[2];
> > -
> >  	struct regulator *reg;
> >  	struct mutex lock;
> >  	const struct mcp320x_chip_info *chip_info;
> > +
> > +	u8 tx_buf ____cacheline_aligned;
> > +	u8 rx_buf[2];
> >  };
> >  
> >  static int mcp320x_channel_to_tx_data(int device_index,
> > 
> 

Re: [PATCH v2] iio: mcp320x: Fix occasional incorrect readings

[jic23]

Michael Welling writes: 

> On Thu, May 07, 2015 at 11:13:15AM +0100, Jonathan Cameron wrote:
>> On 06/05/15 17:49, Michael Welling wrote:
>> > Without the cacheline alignment, the readings will occasionally incorrectly
>> > return 0.
>> > 
>> > Signed-off-by: Michael Welling <mwelling@ieee.org>
>> Applied to the fixes-togreg branch of iio.git.  Not sure
>> when I'll be able to push this out publicly as travelling
>> / working nights and generally having a silly week. 
>> 
>> J
> 
> Thanks. 
> 
> Appearently code can be silly too:
> https://lkml.org/lkml/2015/5/7/879
*laughs*.  Hmm. 8.56pm. Chances are Mark was a beer or two down ;) 

> 
>> > ---
>> > 
>> > v2: Moved buffers to the end of the mcp320x struct per suggestion to keep
>> > them on their own cacheline.
>> > 
>> >  drivers/iio/adc/mcp320x.c |    6 +++---
>> >  1 file changed, 3 insertions(+), 3 deletions(-)
>> > 
>> > diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
>> > index efbfd12..8d9c9b9 100644
>> > --- a/drivers/iio/adc/mcp320x.c
>> > +++ b/drivers/iio/adc/mcp320x.c
>> > @@ -60,12 +60,12 @@ struct mcp320x {
>> >  	struct spi_message msg;
>> >  	struct spi_transfer transfer[2];
>> >  
>> > -	u8 tx_buf;
>> > -	u8 rx_buf[2];
>> > -
>> >  	struct regulator *reg;
>> >  	struct mutex lock;
>> >  	const struct mcp320x_chip_info *chip_info;
>> > +
>> > +	u8 tx_buf ____cacheline_aligned;
>> > +	u8 rx_buf[2];
>> >  };
>> >  
>> >  static int mcp320x_channel_to_tx_data(int device_index,
>> >  
>> 
> --
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