Re: [PATCH v3 11/14] remoteproc: Deal with synchronisation when changing FW image

Mathieu Poirier
2020-04-30T20:32:11Z

On Wed, Apr 29, 2020 at 10:52:48AM +0200, Arnaud POULIQUEN wrote:
>
>
> On 4/24/20 10:01 PM, Mathieu Poirier wrote:
> > This patch prevents the firmware image from being displayed or changed
> > when the remoteproc core is synchronising with a remote processor. This
> > is needed since there is no guarantee about the nature of the firmware
> > image that is loaded by the external entity.
> >
> > Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> > ---
> > drivers/remoteproc/remoteproc_sysfs.c | 24 +++++++++++++++++++++++-
> > 1 file changed, 23 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> > index 7f8536b73295..cdd322a6ecfa 100644
> > --- a/drivers/remoteproc/remoteproc_sysfs.c
> > +++ b/drivers/remoteproc/remoteproc_sysfs.c
> > @@ -13,9 +13,20 @@
> > static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
> > char *buf)
> > {
> > + ssize_t ret;
> > struct rproc *rproc = to_rproc(dev);
> >
> > - return sprintf(buf, "%s\n", rproc->firmware);
> > + /*
> > + * In most instances there is no guarantee about the firmware
> > + * that was loaded by the external entity. As such simply don't
> > + * print anything.
> > + */
> > + if (rproc_needs_syncing(rproc))
> > + ret = sprintf(buf, "\n");
>
> A default name is provided in sysfs if no firmware is started/synchronised on boot.
>
> IMO providing an empty name here could be confusing.
> Perhaps a refactoring of this sysfs entry would be nice:
> - Normal boot (no firmware loaded) : empty name instead of a default name

That is guaranteed to break user space so we can't proceed this way.

> - auto_boot: name provided by the platform driver or default name ( current implementation)
> - synchronization: a predefined name such as Default, unknown, External, None,...

Loic had the same comment. Usually it is best to provide sysfs output that
don't need parsing, i.e 0/1 or nothing at all, but in the remoteproc subsystem
we already have "state", "name" and "firmware" that need parsing. As such my
next revision will have "unknown", which I think is the best way to describe the
situation.

>
> > + else
> > + ret = sprintf(buf, "%s\n", rproc->firmware);
> > +
> > + return ret;
> > }
> >
> > /* Change firmware name via sysfs */
> > @@ -39,6 +50,17 @@ static ssize_t firmware_store(struct device *dev,
> > goto out;
> > }
> >
> > + /*
> > + * There is no point in trying to change the firmware if loading the
> > + * image of the remote processor is done by another entity.
> > + */
> > + if (rproc_needs_syncing(rproc)) {
> > + dev_err(dev,
> > + "can't change firmware while synchronising with MCU\n");
>
> I don't know if you decide to keep "MCU" or not. If not the case
> you have also some other instances in your patch 9/14.

MCU should be long gone. I thought I had spotted them all but was obviously
wrong.

>
> Regards
> Arnaud
>
> > + err = -EBUSY;
> > + goto out;
> > + }
> > +
> > len = strcspn(buf, "\n");
> > if (!len) {
> > dev_err(dev, "can't provide a NULL firmware\n");
> >