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SubjectRe: [PATCH] media: i2c: tvp5150: fix color burst lock instability on some hardware
On Mon, Mar 26, 2018 at 06:43:53AM -0300, Mauro Carvalho Chehab wrote:
> Hi Nasser,
>
> Em Mon, 26 Mar 2018 03:26:33 +0430
> Nasser Afshin <afshin.nasser@gmail.com> escreveu:
>
> > According to the datasheet, INTREQ/GPCL/VBLK should have a pull-up/down
> > resistor if it's been disabled. On hardware that does not have such
> > resistor, we should use the default output enable value.
> > This prevents the color burst lock instability problem.
>

Color burst lock instability is just a side effect of not using the
recommended value for this bit. If we use the recommended setting, we
will support more hardware while not breaking anything.

> If this is hardware-dependent, you should instead store it at
> OF (for SoC) or pass via platform_data (for PCI/USB devices).
>

We have used the recommended value for this bit (as the datasheet
suggests) while we are in tvp5150_init_enable but in tvp5150_s_stream
we are using the wrong value.

Also we have this comment at line 319:
/* Default values as sugested at TVP5150AM1 datasheet */
But as you see, TVP5150_MISC_CTL is not set to its suggested default
value.

> >
> > Signed-off-by: Nasser Afshin <Afshin.Nasser@gmail.com>
> > ---
> > drivers/media/i2c/tvp5150.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/i2c/tvp5150.c b/drivers/media/i2c/tvp5150.c
> > index 2476d812f669..0e9713814816 100644
> > --- a/drivers/media/i2c/tvp5150.c
> > +++ b/drivers/media/i2c/tvp5150.c
> > @@ -328,7 +328,7 @@ static const struct i2c_reg_value tvp5150_init_default[] = {
> > TVP5150_OP_MODE_CTL,0x00
> > },
> > { /* 0x03 */
> > - TVP5150_MISC_CTL,0x01
> > + TVP5150_MISC_CTL,0x21
> > },
> > { /* 0x06 */
> > TVP5150_COLOR_KIL_THSH_CTL,0x10
> > @@ -1072,7 +1072,8 @@ static int tvp5150_s_stream(struct v4l2_subdev *sd, int enable)
> > * Enable the YCbCr and clock outputs. In discrete sync mode
> > * (non-BT.656) additionally enable the the sync outputs.
> > */
> > - val |= TVP5150_MISC_CTL_YCBCR_OE | TVP5150_MISC_CTL_CLOCK_OE;
> > + val |= TVP5150_MISC_CTL_YCBCR_OE | TVP5150_MISC_CTL_CLOCK_OE |
> > + TVP5150_MISC_CTL_INTREQ_OE;
> > if (decoder->mbus_type == V4L2_MBUS_PARALLEL)
> > val |= TVP5150_MISC_CTL_SYNC_OE;
> > }
>
>
>
> Thanks,
> Mauro

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