linux-kernel - Re: [PATCH 07/16] media: i2c: rdacm2x: Fix wake up delay

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Message-ID: <YDMGfQFKWUq9hyDv@pendragon.ideasonboard.com>
Date:   Mon, 22 Feb 2021 03:18:53 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>
Cc:     Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        niklas.soderlund+renesas@...natech.se, geert@...ux-m68k.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/16] media: i2c: rdacm2x: Fix wake up delay

Hi Jacopo,

Thank you for the patch.

On Wed, Feb 17, 2021 at 01:33:01PM +0000, Kieran Bingham wrote:
> On 16/02/2021 17:41, Jacopo Mondi wrote:
> > The MAX9271 chip manual prescribes a delay of 5 milliseconds
> > after the chip exists from low power state.
> > 
> > Adjust the required delay in the rdacm21 camera module and add it
> > to the rdacm20 that currently doesn't implement one.
> 
> This sounds to me like it should be a common function in the max9271 module:
> 
> >         /* Verify communication with the MAX9271: ping to wakeup. */
> >         dev->serializer.client->addr = MAX9271_DEFAULT_ADDR;
> >         i2c_smbus_read_byte(dev->serializer.client);
> >         usleep_range(5000, 8000);
> 
> Especially as that MAX9271_DEFAULT_ADDR should probably be handled
> directly in the max9271.c file too, and the RDACM's shouldn't care about it.

I think this is a good idea. With this addressed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> If we end up moving the max9271 'library' into more of a module/device
> then this would have to be done in it's 'probe' anyway, so it's likely
> better handled down there...?
> 
> But ... it's not essential at this point in the series, so if you want
> to keep this patch as is,
> 
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> 	> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> > ---
> >  drivers/media/i2c/rdacm20.c | 1 +
> >  drivers/media/i2c/rdacm21.c | 2 +-
> >  2 files changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/i2c/rdacm20.c b/drivers/media/i2c/rdacm20.c
> > index ea30cc936531..39e4b4241870 100644
> > --- a/drivers/media/i2c/rdacm20.c
> > +++ b/drivers/media/i2c/rdacm20.c
> > @@ -460,6 +460,7 @@ static int rdacm20_initialize(struct rdacm20_device *dev)
> >  	/* Verify communication with the MAX9271: ping to wakeup. */
> >  	dev->serializer.client->addr = MAX9271_DEFAULT_ADDR;
> >  	i2c_smbus_read_byte(dev->serializer.client);
> > +	usleep_range(5000, 8000);
> >  
> >  	/* Serial link disabled during config as it needs a valid pixel clock. */
> >  	ret = max9271_set_serial_link(&dev->serializer, false);
> > diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c
> > index 179d107f494c..b22a2ca5340b 100644
> > --- a/drivers/media/i2c/rdacm21.c
> > +++ b/drivers/media/i2c/rdacm21.c
> > @@ -453,7 +453,7 @@ static int rdacm21_initialize(struct rdacm21_device *dev)
> >  	/* Verify communication with the MAX9271: ping to wakeup. */
> >  	dev->serializer.client->addr = MAX9271_DEFAULT_ADDR;
> >  	i2c_smbus_read_byte(dev->serializer.client);
> > -	usleep_range(3000, 5000);
> > +	usleep_range(5000, 8000);
> >  
> >  	/* Enable reverse channel and disable the serial link. */
> >  	ret = max9271_set_serial_link(&dev->serializer, false);

-- 
Regards,

Laurent Pinchart