Re: [PATCH 12/16] gpu: ipu-v3: Fix CSI0 blur in NTSC format

[Steve Longerbeam]

On 07/15/2016 05:58 AM, Philipp Zabel wrote:
> Am Mittwoch, den 13.07.2016, 16:02 -0700 schrieb Steve Longerbeam:
> > On 07/10/2016 09:33 AM, Steve Longerbeam wrote:
> > > On 07/08/2016 10:34 AM, Philipp Zabel wrote:
> > > > Am Donnerstag, den 07.07.2016, 16:03 -0700 schrieb Steve Longerbeam:
> > > > > From: Suresh Dhandapani <Suresh.Dhandapani@xxxxxxxxxxxx>
> > > > >
> > > > > This patch will change the register IPU_CSI0_CCIR_CODE_2 value from
> > > > > 0x40596 to 0x405A6. The change is related to the Start of field 1
> > > > > first blanking line command bit[5-3] for NTSC format only. This
> > > > > change is dependent with ADV chip where the NEWAVMODE is set to 0
> > > > > in register 0x31. Setting NEWAVMODE to "0" in ADV means "EAV/SAV
> > > > > codes generated to suit analog devices encoders".
> > > > >
> > > > > Signed-off-by: Suresh Dhandapani <Suresh.Dhandapani@xxxxxxxxxxxx>
> > > > > ---
> > > > >    drivers/gpu/ipu-v3/ipu-csi.c | 2 +-
> > > > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/gpu/ipu-v3/ipu-csi.c b/drivers/gpu/ipu-v3/ipu-csi.c
> > > > > index 0eac28c..ec81958 100644
> > > > > --- a/drivers/gpu/ipu-v3/ipu-csi.c
> > > > > +++ b/drivers/gpu/ipu-v3/ipu-csi.c
> > > > > @@ -422,7 +422,7 @@ int ipu_csi_init_interface(struct ipu_csi *csi,
> > > > >                  ipu_csi_write(csi, 0xD07DF | CSI_CCIR_ERR_DET_EN,
> > > > >                          CSI_CCIR_CODE_1);
> > > > > -            ipu_csi_write(csi, 0x40596, CSI_CCIR_CODE_2);
> > > > > +            ipu_csi_write(csi, 0x405A6, CSI_CCIR_CODE_2);
> > > > >                ipu_csi_write(csi, 0xFF0000, CSI_CCIR_CODE_3);
> > > > >            } else {
> > > > >                dev_err(csi->ipu->dev,
> > > > This looks like a very hardware specific hack? I'll at least have to
> > > > test if that also works with other analog decoders.
> > > Hi Philipp,
> > >
> > > Yes it's a hack, but it has always been a hack (hardcoded values). And the
> > > reason is simple, nobody AFAIK (including me) understands how to program
> > > these CSI_CCIR_CODE registers, the description in the reference manual is
> > > complete gibberish.
> > Hi Philipp, Ian over at linux-media helped me to understand these registers a
> > little better, although there are still mysteries given the poor documentation.
> > You should have been copied on that linux-media thread.
> >
> > > The reason we made this change is that, in discussions with Analog Devices,
> > > they recommended setting NEWAVMODE, which changes the positions of
> > > the AV codes sent by the ADV7180 on the bt.656 bus. It took Suresh at least
> > > a full day of reverse engineering (Suresh correct me if I am wrong) to hit
> > > on the correct values in these registers to regain stable video after switching
> > > the ADV7180 to NEWAVMODE.
> > So this NEWAVMODE is somehow breaking from the BT.656 standard, which
> > necessitated the change to CSI_CCIR_CODE_2. So NEWAVMODE if enabled in
> > the ADV7180 will break other capture backends that are expecting standard
> > BT.656 SAV/EAV codes. So NEWAVMODE should not be used and I will remove
> > this patch in the next version.
> Ok. To use that mode, first a new v4l2 mbus type and corresponding DT
> bindings would have to be added.

Hmm, do you mean define something like a V4L2_MBUS_BT656_NEWAVMODE,
and then add a new "newavmode" boolean DT binding parsed by
v4l2_of_parse_endpoint()?

I don't know if that would make sense given that this NEWAVMODE is a kind
of hack of the BT.656 standard, only used by Analog Devices 
encoders/decoders.

Although there a _lot_ of AD encoder/decoder chips (and subdev drivers 
written for
them), so maybe it would make sense to do this.

Adding Hans.

Steve