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Date:   Mon, 3 Aug 2020 21:28:01 +0200
From:   Niklas <niklas.soderlund@ragnatech.se>
To:     "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media <linux-media@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Biju Das <biju.das.jz@bp.renesas.com>
Subject: Re: [PATCH v2] media: rcar-vin: Add support to select data pins for
 YCbCr422-8bit input
Message-ID: <20200803192801.GC2297236@oden.dyn.berto.se>
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Hi Lad,

On 2020-08-03 20:17:54 +0100, Lad, Prabhakar wrote:
> Hi Niklas,
> 
> Thank you for the review.
> 
> On Mon, Aug 3, 2020 at 7:06 PM Niklas <niklas.soderlund@ragnatech.se> wrote:
> >
> > Hi Lad,
> >
> > Thanks for your work.
> >
> > On 2020-08-03 17:02:53 +0100, Lad Prabhakar wrote:
> > > Select the data pins for YCbCr422-8bit input format depending on
> > > bus_width and data_shift passed as part of DT.
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
> > > ---
> > > Changes for v2:
> > > * Dropped DT binding documentation patch
> > > * Select the data pins depending on bus-width and data-shift
> >
> > I like this v2 much better then v1, nice work!
> >
> > >
> > > v1 -
> > > https://patchwork.kernel.org/project/linux-renesas-soc/list/?series=323799
> > > ---
> > >  drivers/media/platform/rcar-vin/rcar-core.c | 5 +++++
> > >  drivers/media/platform/rcar-vin/rcar-dma.c  | 7 +++++++
> > >  drivers/media/platform/rcar-vin/rcar-vin.h  | 5 +++++
> > >  3 files changed, 17 insertions(+)
> > >
> > > diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> > > index 7440c8965d27..55005d86928d 100644
> > > --- a/drivers/media/platform/rcar-vin/rcar-core.c
> > > +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> > > @@ -624,6 +624,11 @@ static int rvin_parallel_parse_v4l2(struct device *dev,
> > >       vin->parallel = rvpe;
> > >       vin->parallel->mbus_type = vep->bus_type;
> > >
> > > +     /* select VInDATA[15:8] pins for YCbCr422-8bit format */
> > > +     if (vep->bus.parallel.bus_width == BUS_WIDTH_8 &&
> > > +         vep->bus.parallel.data_shift == DATA_SHIFT_8)
> > > +             vin->parallel->ycbcr_8b_g = true;
> > > +
> >
> > I would store the bus_width and bus_shift values in the struct
> > rvin_parallel_entity and evaluate them in place rater then create a flag
> > for this specific use-case..
> >
> Ok will do that.
> 
> > Also according to the documentation is the check correct? Do we not wish
> > to use the new mode when bus_width == 16 and bus_shift == 8. The check
> > you have here seems to describe a 8 lane bus where 0 lanes are used.
> >
> bus-width is the actual data lines used, so bus_width == 16 and
> bus_shift == 8 would mean use lines 23:8, so just check for bus_width
> == 8 and bus_shift == 8 should be sufficient.

As you and Geert points out I was wrong, they should indeed both be 8.

> 
> > I think you should also verify that bus_shift is either 0 or 8 as that
> > is all the driver supports.
> >
> Not sure if thats correct.In that case this patch wont make sense, I
> believed we agreed upon we determine the YDS depending on both
> bus-width and bus-shift.

I'm sorry I think I lost you :-) The driver is not capable of supporting 
bus_width = 8 and bus_shift = 2 right? Maybe we are talking about 
different things.

What I tried to say (updated with the knowledge of that bus_width should 
indeed be 8 and not 16) was that would it make sens to with bus_width=8 
allow for a bus_shift value other then 0 or 8? What for example would 
the driver do if the value was 2?

> 
> On iWave G21D-Q7 for VI2 interface VI2_G* pins are connected to SoC
> and for VIN3 interface Vi3_DATA* pins are connected. So in this case
> the capture only works for VIN2 only if YDS bit is set for 8-bit 422,
> and for VIN3 capture only works if YDS is 0
> 
> &vin2 {
>     status = "okay";
>     pinctrl-0 = <&vin2_pins>;
>     pinctrl-names = "default";
> 
>     port {
>         #address-cells = <1>;
>         #size-cells = <0>;
> 
>         vin2ep: endpoint {
>             remote-endpoint = <&ov7725_2>;
>             bus-width = <8>;
>             data-shift = <8>;
>         };
>     };
> };
> 
> &vin3 {
>     status = "okay";
>     pinctrl-0 = <&vin3_pins>;
>     pinctrl-names = "default";
> 
>     port {
>         #address-cells = <1>;
>         #size-cells = <0>;
> 
>         vin3ep: endpoint {
>             remote-endpoint = <&ov7725_3>;
>             bus-width = <8>;
>         };
>     };
> };
> 
> 
> > >       switch (vin->parallel->mbus_type) {
> > >       case V4L2_MBUS_PARALLEL:
> > >               vin_dbg(vin, "Found PARALLEL media bus\n");
> > > diff --git a/drivers/media/platform/rcar-vin/rcar-dma.c b/drivers/media/platform/rcar-vin/rcar-dma.c
> > > index 1a30cd036371..5db483877d65 100644
> > > --- a/drivers/media/platform/rcar-vin/rcar-dma.c
> > > +++ b/drivers/media/platform/rcar-vin/rcar-dma.c
> > > @@ -127,6 +127,8 @@
> > >  #define VNDMR2_FTEV          (1 << 17)
> > >  #define VNDMR2_VLV(n)                ((n & 0xf) << 12)
> > >
> > > +#define VNDMR2_YDS           BIT(22)
> >
> > This should be grouped with the other VNDMR2_* macros and not on its
> > own. Also it should be sorted so it should be inserted between
> > VNDMR2_CES and VNDMR2_FTEV.
> >
> > Also I know BIT() is a nice macro but the rest of the driver uses (1 <<
> > 22), please do the same for this one.
> >
> Sure will take care of it.
> 
> > > +
> > >  /* Video n CSI2 Interface Mode Register (Gen3) */
> > >  #define VNCSI_IFMD_DES1              (1 << 26)
> > >  #define VNCSI_IFMD_DES0              (1 << 25)
> > > @@ -698,6 +700,11 @@ static int rvin_setup(struct rvin_dev *vin)
> > >               /* Data Enable Polarity Select */
> > >               if (vin->parallel->mbus_flags & V4L2_MBUS_DATA_ENABLE_LOW)
> > >                       dmr2 |= VNDMR2_CES;
> > > +
> > > +             if (vin->parallel->ycbcr_8b_g && vin->mbus_code == MEDIA_BUS_FMT_UYVY8_2X8)
> > > +                     dmr2 |= VNDMR2_YDS;
> > > +             else
> > > +                     dmr2 &= ~VNDMR2_YDS;
> >
> > dmr2 is already unitized and YDS is cleared, no need to clear it again
> > if you don't wish to set it. Taking this and the comments above into
> > account this would become something like (not tested),
> >
> Agreed.
> 
> >     switch (vin->mbus_code) {
> >     case MEDIA_BUS_FMT_UYVY8_2X8:
> >         if (vin->parallel->bus_width == 16 && vin->parallel->bus_shift == 8)
> >             dmr2 |= VNDMR2_YDS;
> >         break;
> >     default:
> >         break;
> >     }
> >
> > >       }
> > >
> > >       /*
> > > diff --git a/drivers/media/platform/rcar-vin/rcar-vin.h b/drivers/media/platform/rcar-vin/rcar-vin.h
> > > index c19d077ce1cb..3126fee9a89b 100644
> > > --- a/drivers/media/platform/rcar-vin/rcar-vin.h
> > > +++ b/drivers/media/platform/rcar-vin/rcar-vin.h
> > > @@ -87,6 +87,9 @@ struct rvin_video_format {
> > >       u8 bpp;
> > >  };
> > >
> > > +#define BUS_WIDTH_8  8
> > > +#define DATA_SHIFT_8 8
> >
> > As pointed out by Geert, not so useful, use 8 in the code :-)
> >
> Agreed will drop it.
> 
> Cheers,
> Prabhakar

-- 
Regards,
Niklas S?derlund