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SubjectRe: [PATCH] media: i2c: adv7180: fix adv7280 BT.656-4 compatibility
Hi Tim,

Sorry for taking to so long to look at this.

On 2019-09-23 15:04:47 -0700, Tim Harvey wrote:
> On Thu, Aug 29, 2019 at 7:29 AM Niklas Söderlund
> <niklas.soderlund@ragnatech.se> wrote:
> >
> > Hi,
> >
> > On 2019-08-29 13:43:49 +0200, Hans Verkuil wrote:
> > > Adding Niklas.
> > >
> > > Niklas, can you take a look at this?
> >
> > I'm happy to have a look at this. I'm currently moving so all my boards
> > are in a box somewhere. I hope to have my lab up and running next week,
> > so if this is not urgent I will look at it then.
> >
>
> Niklas,
>
> Have you looked at this yet? Without this patch the ADV7280A does not
> output proper BT.656. We tested this on a Gateworks Ventana GW5404-G
> which uses the ADV7280A connected to the IMX6 CSI parallel bus. I'm
> hoping to see this get merged and perhaps backported to older kernels.

I only have access to an adv7180 so I was unable to test this patch.
After reviewing the documentation I think the patch is OK if what you
want is to unconditionally switch the driver from outputting BT.656-3 to
outputting BT.656-4.

As this change would effect a large number of compat strings (adv7280,
adv7280-m, adv7281, adv7281-m, adv7281-ma, adv7282, adv7282-m) and the
goal is to back port it I'm a bit reluctant to adding my tag to this
patch as I'm not sure if this will break other setups.

From the documentation about the BT.656-4 register (address 0x04 bit 7):

Between Revision 3 and Revision 4 of the ITU-R BT.656 standards,
the ITU has changed the toggling position for the V bit within
the SAV EAV codes for NTSC. The ITU-R BT.656-4 standard
bit allows the user to select an output mode that is compliant
with either the previous or new standard. For further information,
visit the International Telecommunication Union website.

Note that the standard change only affects NTSC and has no
bearing on PAL.

When ITU-R BT.656-4 is 0 (default), the ITU-R BT.656-3
specification is used. The V bit goes low at EAV of Line 10
and Line 273.

When ITU-R BT.656-4 is 1, the ITU-R BT.656-4 specification is
used. The V bit goes low at EAV of Line 20 and Line 283.

Do you know what effects such a change would bring? Looking at the
driver BT.656-4 seems to be set unconditionally for some adv7180 chips.

>
> Regards,
>
> Tim
>
> > >
> > > Regards,
> > >
> > > Hans
> > >
> > > On 8/27/19 11:55 PM, Matthew Michilot wrote:
> > > > From: Matthew Michilot <matthew.michilot@gmail.com>
> > > >
> > > > Captured video would be out of sync when using the adv7280 with
> > > > the BT.656-4 protocol. Certain registers (0x04, 0x31, 0xE6) had to
> > > > be configured properly to ensure BT.656-4 compatibility.
> > > >
> > > > An error in the adv7280 reference manual suggested that EAV/SAV mode
> > > > was enabled by default, however upon inspecting register 0x31, it was
> > > > determined to be disabled by default.

The manual I have [1] states that NEWAVMODE is switched off by default.
I'm only asking as I would like to know if there is an error in that
datasheet or not.

1. https://www.analog.com/media/en/technical-documentation/user-guides/ADV7280_7281_7282_7283_UG-637.pdf

> > > >
> > > > Signed-off-by: Matthew Michilot <matthew.michilot@gmail.com>
> > > > Reviewed-by: Tim Harvey <tharvey@gateworks.com>
> > > > ---
> > > > drivers/media/i2c/adv7180.c | 15 +++++++++++++--
> > > > 1 file changed, 13 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/media/i2c/adv7180.c b/drivers/media/i2c/adv7180.c
> > > > index 99697baad2ea..27da424dce76 100644
> > > > --- a/drivers/media/i2c/adv7180.c
> > > > +++ b/drivers/media/i2c/adv7180.c
> > > > @@ -94,6 +94,7 @@
> > > > #define ADV7180_REG_SHAP_FILTER_CTL_1 0x0017
> > > > #define ADV7180_REG_CTRL_2 0x001d
> > > > #define ADV7180_REG_VSYNC_FIELD_CTL_1 0x0031
> > > > +#define ADV7180_VSYNC_FIELD_CTL_1_NEWAV 0x12
> > > > #define ADV7180_REG_MANUAL_WIN_CTL_1 0x003d
> > > > #define ADV7180_REG_MANUAL_WIN_CTL_2 0x003e
> > > > #define ADV7180_REG_MANUAL_WIN_CTL_3 0x003f
> > > > @@ -935,10 +936,20 @@ static int adv7182_init(struct adv7180_state *state)
> > > > adv7180_write(state, ADV7180_REG_EXTENDED_OUTPUT_CONTROL, 0x57);
> > > > adv7180_write(state, ADV7180_REG_CTRL_2, 0xc0);
> > > > } else {
> > > > - if (state->chip_info->flags & ADV7180_FLAG_V2)
> > > > + if (state->chip_info->flags & ADV7180_FLAG_V2) {
> > > > + /* ITU-R BT.656-4 compatible */
> > > > adv7180_write(state,
> > > > ADV7180_REG_EXTENDED_OUTPUT_CONTROL,
> > > > - 0x17);
> > > > + ADV7180_EXTENDED_OUTPUT_CONTROL_NTSCDIS);
> > > > + /* Manually set NEWAVMODE */
> > > > + adv7180_write(state,
> > > > + ADV7180_REG_VSYNC_FIELD_CTL_1,
> > > > + ADV7180_VSYNC_FIELD_CTL_1_NEWAV);
> > > > + /* Manually set V bit end position in NTSC mode */
> > > > + adv7180_write(state,
> > > > + ADV7180_REG_NTSC_V_BIT_END,
> > > > + ADV7180_NTSC_V_BIT_END_MANUAL_NVEND);
> > > > + }
> > > > else
> > > > adv7180_write(state,
> > > > ADV7180_REG_EXTENDED_OUTPUT_CONTROL,
> > > >
> > >
> >
> > --
> > Regards,
> > Niklas Söderlund

--
Regards,
Niklas Söderlund

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