Re: [PATCH v2] media: i2c: alvium: Accelerated alvium_set_power

[Martin Hecht]

Hi Sakari,

thank you for your feedback. Please ignore v3 because overlap. I will 
adopt your proposal and send v4. Nevertheless I'm in conversation with 
Ricardo because some eventually misleading feedback from CI to learn how 
to deal with that.

BR Martin

On 9/10/25 17:09, Sakari Ailus wrote:
> Hi Martin,
>
> On Tue, Sep 09, 2025 at 01:22:51PM +0200, Martin Hecht wrote:
> > Now alvium_set_power tests if Alvium is up and running already
> > instead of waiting for the period of a full reboot. This safes
> > about 5-7 seconds delay for each connected camera what is already
> > booted especially when using multiple Alvium cameras or using
> > camera arrays.
> > The new function alvium_check is used by read_poll_timeout to check
> > whether a camera is connected on I2C and if it responds already.
> >
> > Signed-off-by: Martin Hecht <mhecht73@xxxxxxxxx>
> > ---
> > v2:
> > - added alvium_check to be used by read_poll_timeout as
> >    suggested by Sakari
> > ---
> >   drivers/media/i2c/alvium-csi2.c | 32 +++++++++++++++++++++++++-------
> >   1 file changed, 25 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/media/i2c/alvium-csi2.c b/drivers/media/i2c/alvium-csi2.c
> > index 5c1bab574394..c63af96d3b31 100644
> > --- a/drivers/media/i2c/alvium-csi2.c
> > +++ b/drivers/media/i2c/alvium-csi2.c
> > @@ -443,10 +443,8 @@ static int alvium_is_alive(struct alvium_dev *alvium)
> >   
> >   	alvium_read(alvium, REG_BCRM_MINOR_VERSION_R, &bcrm, &ret);
> >   	alvium_read(alvium, REG_BCRM_HEARTBEAT_RW, &hbeat, &ret);
> > -	if (ret)
> > -		return ret;
> >   
> > -	return hbeat;
> > +	return ret;
> >   }
> >   
> >   static void alvium_print_avail_mipi_fmt(struct alvium_dev *alvium)
> > @@ -2364,8 +2362,25 @@ static int alvium_get_dt_data(struct alvium_dev *alvium)
> >   	return -EINVAL;
> >   }
> >   
> > +static int alvium_check(struct alvium_dev *alvium, u64 *bcrm_major)
> > +{
> > +	struct device *dev = &alvium->i2c_client->dev;
> > +	int ret = 0;
>
> No need to assign ret here.
>
> > +
> > +	ret = alvium_read(alvium, REG_BCRM_MAJOR_VERSION_R, bcrm_major, NULL);
> > +
>
> No need for an empty line here.
>
> But see below...
>
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (*bcrm_major != 0)
> > +		return 0;
> > +
> > +	return -ENODEV;
> > +}
> > +
> >   static int alvium_set_power(struct alvium_dev *alvium, bool on)
> >   {
> > +	u64 bcrm_major = 0;
> >   	int ret;
> >   
> >   	if (!on)
> > @@ -2375,9 +2390,12 @@ static int alvium_set_power(struct alvium_dev *alvium, bool on)
> >   	if (ret)
> >   		return ret;
> >   
> > -	/* alvium boot time 7s */
> > -	msleep(7000);
> > -	return 0;
> > +	/* alvium boot time is up to 7.5s but test if its available already */
> > +	read_poll_timeout(alvium_check, bcrm_major, (bcrm_major == 0),
> > +		250000, 7500000, false,
> > +		alvium, &bcrm_major);
>
> I presume bcrm_major needs to be non-zero to proceed rather than zero?
>
> I think you could also do:
>
> 	read_poll_timeout(alvium_read, ret, !ret && brcm_major, 250000, 7500000,
> 			  false, alvium, REG_BCRM_MAJOR_VERSION_R, bcrm_major,
> 			  NULL);
>
> 	return ret ?: brcm_major ? 0 : -ENODEV;
>
> > +
> > +	return ret;
> >   }
> >   
> >   static int alvium_runtime_resume(struct device *dev)
> > @@ -2442,7 +2460,7 @@ static int alvium_probe(struct i2c_client *client)
> >   	if (ret)
> >   		goto err_powerdown;
> >   
> > -	if (!alvium_is_alive(alvium)) {
> > +	if (alvium_is_alive(alvium)) {
>
> If you prefer to change this, then I'd assign the return value to ret, as
> returned by alvium_read() and use it as the error code here, too. But this
> should be a separate patch.
>
> >   		ret = -ENODEV;
> >   		dev_err_probe(dev, ret, "Device detection failed\n");
> >   		goto err_powerdown;