Re: [PATCH v2 07/14] remoteproc: Introduce function __rproc_detach()

[Arnaud POULIQUEN <arnaud.pouliquen@st.com>]

On 10/30/20 8:57 PM, Mathieu Poirier wrote:
> Introduce function __rproc_detach() to perform the same kind of
> operation as rproc_stop(), but instead of switching off the
> remote processor using rproc->ops->stop(), it uses
> rproc->ops->detach().  That way it is possible for the core
> to release the resources associated with a remote processor while
> the latter is kept operating.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> Reviewed-by: Peng Fan <peng.fan@nxp.com>
> ---
>  drivers/remoteproc/remoteproc_core.c | 31 ++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index ed1f9ca4248b..62e88ff65009 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1664,6 +1664,37 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
>  	return 0;
>  }
>  
> +/*
> + * __rproc_detach(): Does the opposite of rproc_attach()
> + */
> +static int __maybe_unused __rproc_detach(struct rproc *rproc)
> +{
> +	struct device *dev = &rproc->dev;
> +	int ret;
> +
> +	/* No need to continue if a detach() operation has not been provided */
> +	if (!rproc->ops->detach)
> +		return -EINVAL;
> +
> +	/* Stop any subdevices for the remote processor */
> +	rproc_stop_subdevices(rproc, false);

How to determine whether a subdevice should be stopped or detached? 
For instance, in ST, we have a resource manager subdev which maintains clocks and regulators
for peripherals used by the remote processor.
In case of detachment we would need to maintain clock and regulators.

> +
> +	/* Tell the remote processor the core isn't available anymore */
> +	ret = rproc->ops->detach(rproc);
> +	if (ret) {
> +		dev_err(dev, "can't detach from rproc: %d\n", ret);
> +		rproc_start_subdevices(rproc);
> +		return ret;
> +	}
> +
> +	rproc_unprepare_subdevices(rproc);

Same here, is prepare/unprepare can depend on the operation?

Seems that adding rproc_attach_subdevices/rproc_detach_subdevices could be not sufficient
to address prepare/unprepare.
Alternative could be:
- extra parameter for the subdev ops to indicate attach/detach action...?
- intermediate rproc state : ATTACHING, DETACHING
- other?

That's said, I don't think that it is blocking for the ST resource manager.
In this particular case, regulators and clocks can be permanently activated
as a back-up solution (always-on).

So, if no other company has a problem with that, we can keep this implementation for now.

Regards,
Arnaud

> +
> +	rproc->state = RPROC_DETACHED;
> +
> +	dev_info(dev, "detached remote processor %s\n", rproc->name);
> +
> +	return 0;
> +}
>  
>  /**
>   * rproc_trigger_recovery() - recover a remoteproc
>