Re: [PATCH v1 03/12] media: i2c: mt9m111: Skip chid identification

[jmondi]

Hi Laurent,

On Tue, Jun 20, 2017 at 10:48:21AM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Monday 19 Jun 2017 19:04:40 Jacopo Mondi wrote:
> > Reads of chip identification code (both on registers 0x00 and 0xff)
> > always return 0x00.
>
> This shouldn't be the case. It might mean that your I2C master controller
> doesn't handle reads correctly. I don't think this patch is correct.

Indeed this patch was not meant for inclusion (as it is part of an RFC series)
but I still fail to read the chip identifier even when using a tool to
sniff the bus or talk directly to the chip (I'm using bus pirate
for this purpose).

What puzzles me is that I get back reads from some registers that match the
defaults reported by the data sheet, while other registers return
meaningful values but different from what I have indicated as defaults
in the sensor manual, while chip identifier reads always back as 0x00.

I am pasting some examples down here of some interactions with the
chip using bus pirate serial control console [1]

I wonder if I am working with a different chip revision from the one
the driver and the datasheet have as reference, but it really seems
unlikely to me..

Thanks
   j


[1]
** Read register 0x106: expected value 0x700E -> got it!
I2C>[0x90+0xf0+0x00+0x1]
I2C START BIT
WRITE: 0x90 ACK
WRITE: 0xF0 ACK
WRITE: 0x00 ACK
WRITE: 0x01 ACK
I2C STOP BIT
I2C>[0x90+0x06+[0x91+rr]
I2C START BIT
WRITE: 0x90 ACK
WRITE: 0x06 ACK
I2C START BIT
WRITE: 0x91 ACK
READ: 0x70
READ:  ACK 0x0E
NACK
I2C STOP BIT

** Read register 0x108: expected value 0x0080 -> got 0xc800
I2C>[0x90+0xf0+0x00+0x1]
I2C START BIT
WRITE: 0x90 ACK
WRITE: 0xF0 ACK
WRITE: 0x00 ACK
WRITE: 0x01 ACK
I2C STOP BIT
I2C>[0x90+0x08+[0x91+rr]
I2C START BIT
WRITE: 0x90 ACK
WRITE: 0x08 ACK
I2C START BIT
WRITE: 0x91 ACK
READ: 0xC8
READ:  ACK 0x00
NACK
I2C STOP BIT

** Read Chip ID: expected value 0x143a -> got 0x
I2C>[0x90+0xf0+0x00+0x0]
I2C START BIT
WRITE: 0x90 ACK
WRITE: 0xF0 ACK
WRITE: 0x00 ACK
WRITE: 0x00 ACK
I2C STOP BIT
I2C>[0x90+0x00+[0x91+rr]
I2C START BIT
WRITE: 0x90 ACK
WRITE: 0x00 ACK
I2C START BIT
WRITE: 0x91 ACK
READ: 0x00
READ:  ACK 0x00
NACK
I2C STOP BIT

>
> > Skip chip identification to have the device complete probing.
> >
> > Signed-off-by: Jacopo Mondi 
> > ---
> >  drivers/media/i2c/mt9m111.c | 19 ---
> >  1 file changed, 19 deletions(-)
> >
> > diff --git a/drivers/media/i2c/mt9m111.c b/drivers/media/i2c/mt9m111.c
> > index 72e71b7..8e86d51 100644
> > --- a/drivers/media/i2c/mt9m111.c
> > +++ b/drivers/media/i2c/mt9m111.c
> > @@ -890,31 +890,12 @@ static struct v4l2_subdev_ops mt9m111_subdev_ops = {
> >  static int mt9m111_video_probe(struct i2c_client *client)
> >  {
> > struct mt9m111 *mt9m111 = to_mt9m111(client);
> > -   s32 data;
> > int ret;
> >
> > ret = mt9m111_s_power(>subdev, 1);
> > if (ret < 0)
> > return ret;
> >
> > -   data = reg_read(CHIP_VERSION);
> > -
> > -   switch (data) {
> > -   case 0x143a: /* MT9M111 or MT9M131 */
> > -   dev_info(>dev,
> > -   "Detected a MT9M111/MT9M131 chip ID %x\n", data);
> > -   break;
> > -   case 0x148c: /* MT9M112 */
> > -   dev_info(>dev, "Detected a MT9M112 chip ID %x\n",
> data);
> > -   break;
> > -   default:
> > -   dev_err(>dev,
> > -   "No MT9M111/MT9M112/MT9M131 chip detected register
> read %x\n",
> > -   data);
> > -   ret = -ENODEV;
> > -   goto done;
> > -   }
> > -
> > ret = mt9m111_init(mt9m111);
> > if (ret)
> > goto done;
>
> --
> Regards,
>
> Laurent Pinchart
>

Re: [PATCH v1 03/12] media: i2c: mt9m111: Skip chid identification

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Monday 19 Jun 2017 19:04:40 Jacopo Mondi wrote:
> Reads of chip identification code (both on registers 0x00 and 0xff)
> always return 0x00.

This shouldn't be the case. It might mean that your I2C master controller 
doesn't handle reads correctly. I don't think this patch is correct.

> Skip chip identification to have the device complete probing.
>
> Signed-off-by: Jacopo Mondi 
> ---
>  drivers/media/i2c/mt9m111.c | 19 ---
>  1 file changed, 19 deletions(-)
> 
> diff --git a/drivers/media/i2c/mt9m111.c b/drivers/media/i2c/mt9m111.c
> index 72e71b7..8e86d51 100644
> --- a/drivers/media/i2c/mt9m111.c
> +++ b/drivers/media/i2c/mt9m111.c
> @@ -890,31 +890,12 @@ static struct v4l2_subdev_ops mt9m111_subdev_ops = {
>  static int mt9m111_video_probe(struct i2c_client *client)
>  {
>   struct mt9m111 *mt9m111 = to_mt9m111(client);
> - s32 data;
>   int ret;
> 
>   ret = mt9m111_s_power(>subdev, 1);
>   if (ret < 0)
>   return ret;
> 
> - data = reg_read(CHIP_VERSION);
> -
> - switch (data) {
> - case 0x143a: /* MT9M111 or MT9M131 */
> - dev_info(>dev,
> - "Detected a MT9M111/MT9M131 chip ID %x\n", data);
> - break;
> - case 0x148c: /* MT9M112 */
> - dev_info(>dev, "Detected a MT9M112 chip ID %x\n", 
data);
> - break;
> - default:
> - dev_err(>dev,
> - "No MT9M111/MT9M112/MT9M131 chip detected register 
read %x\n",
> - data);
> - ret = -ENODEV;
> - goto done;
> - }
> -
>   ret = mt9m111_init(mt9m111);
>   if (ret)
>   goto done;

-- 
Regards,

Laurent Pinchart