linux-kernel - Re: [PATCH 3/4] media: mt9m111: fix device power usage

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Date:   Fri, 19 Aug 2022 09:32:55 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Jacopo Mondi <jacopo@...ndi.org>
Cc:     mchehab@...nel.org, sakari.ailus@...ux.intel.com,
        laurent.pinchart+renesas@...asonboard.com,
        jacopo+renesas@...ndi.org, akinobu.mita@...il.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de
Subject: Re: [PATCH 3/4] media: mt9m111: fix device power usage

Hi Jacopo,

On 22-08-19, Jacopo Mondi wrote:
> Hi Marco
> 
> On Thu, Aug 18, 2022 at 04:47:11PM +0200, Marco Felsch wrote:
> > Currently the driver turn off the power after probe and toggle it during
> > .stream by using the .s_power callback. This is problematic since other
> > callbacks like .set_fmt accessing the hardware as well which will fail.
> 
> Ouch!
> 
> > So in the end the default format is the only supported format.
> >
> > Remove the hardware register access from the callbacks and instead sync
> > the state once right before the stream gets enabled to fix this.
> 
> Where does it happen in this patch ?

during mt9m111_s_power which gets called by s_power() or after this
small series during s_stream().

> >
> > Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> > ---
> >  drivers/media/i2c/mt9m111.c | 20 +++++++++++++-------
> >  1 file changed, 13 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/media/i2c/mt9m111.c b/drivers/media/i2c/mt9m111.c
> > index 53c4dac4e4bd..cd74c408e110 100644
> > --- a/drivers/media/i2c/mt9m111.c
> > +++ b/drivers/media/i2c/mt9m111.c
> > @@ -481,8 +481,6 @@ static int mt9m111_set_selection(struct v4l2_subdev *sd,
> >  	width = min(mt9m111->width, rect.width);
> >  	height = min(mt9m111->height, rect.height);
> >
> > -
> 
> Why in mainline I don't see these empty lines ?

Hm.. because I introduced this during my "media: mt9m111: fix subdev API
usage" patch.. Sorry.

> > -	mt9m111_setup_geometry(mt9m111, &rect, width, height, mt9m111->fmt->code);
> >  	mt9m111->rect = rect;
> >  	mt9m111->width = width;
> >  	mt9m111->height = height;
> > @@ -611,7 +609,6 @@ static int mt9m111_set_pixfmt(struct mt9m111 *mt9m111,
> >  	if (mt9m111->pclk_sample == 0)
> >  		mask_outfmt2 |= MT9M111_OUTFMT_INV_PIX_CLOCK;
> >
> > -
> >  	mt9m111_reg_mask(client, context_a.output_fmt_ctrl2,
> >  			 data_outfmt2, mask_outfmt2);
> >  	mt9m111_reg_mask(client, context_b.output_fmt_ctrl2,
> > @@ -678,9 +675,6 @@ static int mt9m111_set_fmt(struct v4l2_subdev *sd,
> >  		return 0;
> >  	}
> >
> > -
> > -	mt9m111_setup_geometry(mt9m111, rect, mf->width, mf->height, mf->code);
> > -	mt9m111_set_pixfmt(mt9m111, mf->code);
> 
> Are we looking at two different versions of the driver ??
> https://elixir.bootlin.com/linux/latest/source/drivers/media/i2c/mt9m111.c#L684

Same here.

> >  	mt9m111->width	= mf->width;
> >  	mt9m111->height	= mf->height;
> >  	mt9m111->fmt	= fmt;
> > @@ -743,6 +737,8 @@ mt9m111_find_mode(struct mt9m111 *mt9m111, unsigned int req_fps,
> >  	return mode;
> >  }
> >
> > +static int mt9m111_s_power(struct v4l2_subdev *sd, int on);
> > +
> >  #ifdef CONFIG_VIDEO_ADV_DEBUG
> >  static int mt9m111_g_register(struct v4l2_subdev *sd,
> >  			      struct v4l2_dbg_register *reg)
> > @@ -753,10 +749,14 @@ static int mt9m111_g_register(struct v4l2_subdev *sd,
> >  	if (reg->reg > 0x2ff)
> >  		return -EINVAL;
> >
> > +	mt9m111_s_power(sd, 1);
> > +
> >  	val = mt9m111_reg_read(client, reg->reg);
> >  	reg->size = 2;
> >  	reg->val = (u64)val;
> >
> > +	mt9m111_s_power(sd, 0);
> > +
> >  	if (reg->val > 0xffff)
> >  		return -EIO;
> >
> > @@ -771,9 +771,13 @@ static int mt9m111_s_register(struct v4l2_subdev *sd,
> >  	if (reg->reg > 0x2ff)
> >  		return -EINVAL;
> >
> > +	mt9m111_s_power(sd, 1);
> > +
> >  	if (mt9m111_reg_write(client, reg->reg, reg->val) < 0)
> >  		return -EIO;
> >
> > +	mt9m111_s_power(sd, 0);
> > +
> >  	return 0;
> >  }
> >  #endif
> > @@ -896,6 +900,9 @@ static int mt9m111_s_ctrl(struct v4l2_ctrl *ctrl)
> >  					       struct mt9m111, hdl);
> >  	int ret;
> >
> > +	if (!mt9m111->is_streaming)
> > +		return 0;
> > +
> >  	switch (ctrl->id) {
> >  	case V4L2_CID_VFLIP:
> >  		ret = mt9m111_set_flip(mt9m111, ctrl->val,
> > @@ -927,7 +934,6 @@ static int mt9m111_s_ctrl(struct v4l2_ctrl *ctrl)
> >  		ret = -EINVAL;
> >  	}
> >
> > -
> >  	return ret;
> >  }
> >
> > --
> > 2.30.2
> >
>