linux-kernel - Re: [PATCH] media: i2c: OV5647: gate clock lane before stream on

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Message-ID: <CAFLEztQcCijnmkp_r3-gy2ptM0b+WFEw4Sf1MeiatJbvnKqA8A@mail.gmail.com>
Date:   Mon, 7 Aug 2017 19:06:17 +0800
From:   Jacob Chen <jacobchen110@...il.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, roliveir@...opsys.com,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        vladimir_zapolskiy@...tor.com,
        Hans Verkuil <hans.verkuil@...co.com>,
        sakari.ailus@...ux.intel.com, slongerbeam@...il.com,
        robh+dt@...nel.org, lolivei@...opsys.com
Subject: Re: [PATCH] media: i2c: OV5647: gate clock lane before stream on

Hi Philipp,

2017-08-07 16:17 GMT+08:00 Philipp Zabel <p.zabel@...gutronix.de>:
> Hi Jacob,
>
> On Mon, 2017-08-07 at 15:11 +0800, Jacob Chen wrote:
>> Hi all,
>>
>> 2017-07-25 10:34 GMT+08:00 Jacob Chen <jacob-chen@...wrt.com>:
>> > According to datasheet, BIT5 in reg-0x4800 are used to
>> > enable/disable clock lane gate.
>> >
>> > It's wrong to make clock lane free running before
>> > sensor stream on was called, while the mipi phy
>> > are not initialized.
>> >
>> > Signed-off-by: Jacob Chen <jacob-chen@...wrt.com>
>>>
>> > ---
>> >  drivers/media/i2c/ov5647.c | 10 +++++++++-
>> >  1 file changed, 9 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/media/i2c/ov5647.c b/drivers/media/i2c/ov5647.c
>> > index 95ce90f..d3e6fd0 100644
>> > --- a/drivers/media/i2c/ov5647.c
>> > +++ b/drivers/media/i2c/ov5647.c
>> > @@ -253,6 +253,10 @@ static int ov5647_stream_on(struct v4l2_subdev *sd)
>> >  {
>> >         int ret;
>> >
>> > +       ret = ov5647_write(sd, 0x4800, 0x04);
>> > +       if (ret < 0)
>> > +               return ret;
>> > +
>> >         ret = ov5647_write(sd, 0x4202, 0x00);
>> >         if (ret < 0)
>> >                 return ret;
>> > @@ -264,6 +268,10 @@ static int ov5647_stream_off(struct v4l2_subdev *sd)
>> >  {
>> >         int ret;
>> >
>> > +       ret = ov5647_write(sd, 0x4800, 0x25);
>> > +       if (ret < 0)
>> > +               return ret;
>> > +
>> >         ret = ov5647_write(sd, 0x4202, 0x0f);
>> >         if (ret < 0)
>> >                 return ret;
>> > @@ -320,7 +328,7 @@ static int __sensor_init(struct v4l2_subdev *sd)
>> >                         return ret;
>> >         }
>> >
>> > -       return ov5647_write(sd, 0x4800, 0x04);
>> > +       return ov5647_stream_off(sd);
>> >  }
>> >
>> >  static int ov5647_sensor_power(struct v4l2_subdev *sd, int on)
>> > --
>> > 2.7.4
>> >
>>
>> Can anyone comment on it?
>>
>> I saw there is a same discussion in  https://patchwork.kernel.org/patch/9569031/
>> There is a comment in i.MX CSI2 driver.
>> "
>> Configure MIPI Camera Sensor to put all Tx lanes in LP-11 state.
>> This must be carried out by the MIPI sensor's s_power(ON) subdev
>> op.
>> "
>> That's what this patch do, sensor driver should make sure that clock
>> lanes are in stop state while not streaming.
>
> This is not the same, as far as I can tell. BIT(5) is just clock lane
> gating, as you describe above. To put the bus into LP-11 state, BIT(2)
> needs to be set.
>

Yeah, but i double that clock lane is not in LP11 when continue clock
mode is enabled.

> regards
> Philipp
>