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From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Jacopo Mondi <jacopo+renesas@jmondi.org>
Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
	niklas.soderlund+renesas@ragnatech.se, geert@linux-m68k.org,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 01/16] media: i2c: rdacm20: Enable noise immunity
Date: Mon, 22 Feb 2021 02:49:34 +0200	[thread overview]
Message-ID: <YDL/npLVS7vk3TV7@pendragon.ideasonboard.com> (raw)
In-Reply-To: <5691f68f-724d-9d6a-9ea8-1e017b305c66@ideasonboard.com>

Hi Jacopo,

Thank you for the patch.

On Wed, Feb 17, 2021 at 12:55:19PM +0000, Kieran Bingham wrote:
> On 16/02/2021 17:41, Jacopo Mondi wrote:
> > Enable the noise immunity threshold at the end of the rdacm20
> > initialization routine.
> > 
> > The rdcam20 camera module has been so far tested with a startup

s/rdcam20/rdacm20/

> > delay that allowed the embedded MCU to program the serializer. If
> > the initialization routine is run before the MCU programs the
> > serializer and the image sensor and their addresses gets changed
> > by the rdacm20 driver it is required to manually enable the noise
> > immunity threshold to make the communication on the control channel
> > more reliable.
> 
> Oh, this is interesting, ... booting up without the delays would be ...
> much nicer.

I second that, but I'm a bit worried. The MCU has caused us more pain
than gain, the best way to fix it may be with a desoldering station ;-)
Jokes aside, if we want to start initializing with the serializer before
the MCU completes its initialization, then we'll have a racy process,
with two I2C masters configuring the same device. I don't think anything
good can come out of that :-S

Taking into account the fact that on some platforms we'll want to
implement power management for the cameras, disabling power (possibly
individually) when the cameras are not in use, we'll have to handle the
race carefully, and I'm not sure there any other way than waiting for
the camera to be initialized with an initialization delay after power
up.

Based on this, I'm not concerned about this patch in particular, but
potentially about the series as a whole. I'll comment on individual
patches as applicable.

Regarding this patch, doies the MCU enable high threshold for the
reverse channel as part of its initialization procedure ? Do we have a
full list of what it configures in the MAX9271 ? If so, could we capture
it in a comment in the driver ? That would be very helpful as a
reference.

> > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> > ---
> >  drivers/media/i2c/rdacm20.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/i2c/rdacm20.c b/drivers/media/i2c/rdacm20.c
> > index 90eb73f0e6e9..f7fd5ae955d0 100644
> > --- a/drivers/media/i2c/rdacm20.c
> > +++ b/drivers/media/i2c/rdacm20.c
> > @@ -541,7 +541,13 @@ static int rdacm20_initialize(struct rdacm20_device *dev)
> >  
> >  	dev_info(dev->dev, "Identified MAX9271 + OV10635 device\n");
> >  
> > -	return 0;
> > +	/*
> > +	 * Set reverse channel high threshold to increase noise immunity.
> > +	 *
> > +	 * This should be compensated by increasing the reverse channel
> > +	 * amplitude on the remote deserializer side.
> > +	 */
> > +	return max9271_set_high_threshold(&dev->serializer, true);
> 
> Does this work 'out of the box' ? I.e. if this patch is applied, I
> assume it is required to remove the regulator delays that I/we have in DT?
> 
> Likewise, does that note mean this patch must also be accompanied by the
> update in max9286 somehow?
> 
> I guess we can't keep 'test bisectability' with this very easily so it
> probably doesn't matter too much, the end result will be the interesting
> part.
> 
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
> 
> >  }
> >  
> >  static int rdacm20_probe(struct i2c_client *client)

-- 
Regards,

Laurent Pinchart

  reply	other threads:[~2021-02-22  0:51 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-16 17:41 [PATCH 00/16] media: i2c: GMSL reliability improvements Jacopo Mondi
2021-02-16 17:41 ` [PATCH 01/16] media: i2c: rdacm20: Enable noise immunity Jacopo Mondi
2021-02-17 12:55   ` Kieran Bingham
2021-02-22  0:49     ` Laurent Pinchart [this message]
2021-02-22 14:59       ` Jacopo Mondi
2021-02-24 20:35         ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 02/16] media: i2c: rdacm20: Embedded 'serializer' field Jacopo Mondi
2021-02-17 12:56   ` Kieran Bingham
2021-02-22  0:58   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 03/16] media: i2c: rdacm20: Replace goto with a loop Jacopo Mondi
2021-02-17 13:01   ` Kieran Bingham
2021-02-22  1:05     ` Laurent Pinchart
2021-02-22 15:06       ` Jacopo Mondi
2021-02-24 20:27         ` Laurent Pinchart
2021-02-25  8:56           ` Kieran Bingham
2021-02-16 17:41 ` [PATCH 04/16] media: i2c: rdacm20: Report camera module name Jacopo Mondi
2021-02-17 13:02   ` Kieran Bingham
2021-02-22  1:06   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 05/16] media: i2c: rdacm20: Check return values Jacopo Mondi
2021-02-17 13:08   ` Kieran Bingham
2021-02-22  1:09   ` Laurent Pinchart
2021-02-22 15:08     ` Jacopo Mondi
2021-02-16 17:41 ` [PATCH 06/16] media: i2c: rdacm20: Re-work ov10635 reset Jacopo Mondi
2021-02-17 13:22   ` Kieran Bingham
2021-02-22  1:15   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 07/16] media: i2c: rdacm2x: Fix wake up delay Jacopo Mondi
2021-02-17  8:02   ` Geert Uytterhoeven
2021-02-17 13:33   ` Kieran Bingham
2021-02-22  1:18     ` Laurent Pinchart
2021-02-22 15:11       ` Jacopo Mondi
2021-02-24 20:29         ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 08/16] media: i2c: max9286: Adjust parameters indent Jacopo Mondi
2021-02-17 13:36   ` Kieran Bingham
2021-02-22  1:20   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 09/16] media: i2c: rdacm21: Re-work OV10640 initialization Jacopo Mondi
2021-02-17  8:06   ` Geert Uytterhoeven
2021-02-17 13:55   ` Kieran Bingham
2021-02-22  1:27   ` Laurent Pinchart
2021-02-22 15:19     ` Jacopo Mondi
2021-02-24 20:30       ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 10/16] media: i2c: max9286: Rename reverse_channel_mv Jacopo Mondi
2021-02-17  8:07   ` Geert Uytterhoeven
2021-02-18 15:06   ` Kieran Bingham
2021-02-22  1:29   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 11/16] media: i2c: max9286: Cache channel amplitude Jacopo Mondi
2021-02-17  8:08   ` Geert Uytterhoeven
2021-02-18 15:39   ` Kieran Bingham
2021-02-22  1:33   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 12/16] media: i2c: max9286: Define high " Jacopo Mondi
2021-02-18 15:39   ` Kieran Bingham
2021-02-22  1:35   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 13/16] media: i2c: rdacm2x: Implement .init() subdev op Jacopo Mondi
2021-02-17  8:17   ` Geert Uytterhoeven
2021-02-18 16:13   ` Kieran Bingham
2021-02-22  1:52     ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 14/16] media: i2c: max9286: Initialize remotes when bound Jacopo Mondi
2021-02-17  8:19   ` Geert Uytterhoeven
2021-02-18 16:00   ` Kieran Bingham
2021-02-22  2:03   ` Laurent Pinchart
2021-02-16 17:41 ` [PATCH 15/16] media: i2c: max9286: Rework comments in .bound() Jacopo Mondi
2021-02-18 16:03   ` Kieran Bingham
2021-02-16 17:41 ` [PATCH 16/16] media: i2c: gmsl: Use 339Kbps I2C bit-rate Jacopo Mondi
2021-02-17  8:19   ` Geert Uytterhoeven
2021-02-18 16:07   ` Kieran Bingham
2021-02-22  2:06     ` Laurent Pinchart

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