Re: [PATCH v9 4/7] remoteproc: core: Add TEE interface support for firmware release

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Wed, Sep 18, 2024 at 04:43:32PM +0200, Arnaud POULIQUEN wrote:
> Hello Mathieu,
> 
> On 8/30/24 11:51, Arnaud Pouliquen wrote:
> > Add support for releasing remote processor firmware through
> > the Trusted Execution Environment (TEE) interface.
> > 
> > The tee_rproc_release_fw() function is called in the following cases:
> > 
> > - An error occurs in rproc_start() between the loading of the segments and
> >   the start of the remote processor.
> > - When rproc_release_fw is called on error or after stopping the remote
> >   processor.
> > 
> > Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
> > ---
> >  drivers/remoteproc/remoteproc_core.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> > index 7694817f25d4..32052dedc149 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -29,6 +29,7 @@
> >  #include <linux/debugfs.h>
> >  #include <linux/rculist.h>
> >  #include <linux/remoteproc.h>
> > +#include <linux/remoteproc_tee.h>
> >  #include <linux/iommu.h>
> >  #include <linux/idr.h>
> >  #include <linux/elf.h>
> > @@ -1258,6 +1259,9 @@ static int rproc_alloc_registered_carveouts(struct rproc *rproc)
> >  
> >  static void rproc_release_fw(struct rproc *rproc)
> >  {
> > +	if (rproc->state == RPROC_OFFLINE && rproc->tee_interface)
> > +		tee_rproc_release_fw(rproc);
> 
> I'm requesting you expertise to fix an issue I'm facing during my test preparing
> the V10.
> 
> My issue is that here, we can call the tee_rproc_release_fw() function, defined
> in remoteproc_tee built as a remoteproc_tee.ko module.
> 
> I tried to use the IS_ENABLED and IS_REACHABLE macros in remoteproc_tee.h, but
> without success:
> - use IS_ENABLED() results in a link error: "undefined reference to
> tee_rproc_release_fw."
> - use IS_REACHABLE() returns false and remoteproc_core calls the inline
> tee_rproc_release_fw function that just call WARN_ON(1).
> 
> To solve the issue, I can see three alternatives:
> 
> 1) Modify Kconfig and remoteproc_tee.c to support only built-in.
> 2) Use symbol_get/symbol_put.
> 3) Define a new rproc_ops->release_fw operation that will be initialized to
> tee_rproc_release_fw.
>

Option (1) is best but make sure people can disable the TEE interface if they
don't wish to use it.

> From my perspective, the solution 3 seems to be the cleanest way, as it also
> removes the dependency between remoteproc_core.c and remoteproc_tee.c. But
> regarding previous discussion/series version, it seems that it could not be your
> preferred solution.
> 
> Please, could you indicate your preference so that I can directly implement the
> best solution (or perhaps you have another alternative to propose)?
> 
> Thanks in advance!
> 
> Arnaud
> 
> 
> > +
> >  	/* Free the copy of the resource table */
> >  	kfree(rproc->cached_table);
> >  	rproc->cached_table = NULL;
> > @@ -1348,7 +1352,7 @@ static int rproc_start(struct rproc *rproc, const struct firmware *fw)
> >  	if (ret) {
> >  		dev_err(dev, "failed to prepare subdevices for %s: %d\n",
> >  			rproc->name, ret);
> > -		goto reset_table_ptr;
> > +		goto release_fw;
> >  	}
> >  
> >  	/* power up the remote processor */
> > @@ -1376,7 +1380,9 @@ static int rproc_start(struct rproc *rproc, const struct firmware *fw)
> >  	rproc->ops->stop(rproc);
> >  unprepare_subdevices:
> >  	rproc_unprepare_subdevices(rproc);
> > -reset_table_ptr:
> > +release_fw:
> > +	if (rproc->tee_interface)
> > +		tee_rproc_release_fw(rproc);
> >  	rproc->table_ptr = rproc->cached_table;
> >  
> >  	return ret;