Re: [PATCH 11/14] fsi: Improve master indexing

[Eddie James]

On 8/9/23 02:08, Joel Stanley wrote:
> On Mon, 12 Jun 2023 at 19:57, Eddie James <eajames@xxxxxxxxxxxxx> wrote:
> > Master indexing is problematic if a hub is rescanned while the
> > root master is being rescanned. Move the IDA free below the device
> > unregistration, lock the scan mutex in the probe function, and
> > request a specific idx in the hub driver.
> I've applied this series, but taking a closer look at this patch I
> think it can be improved. If you resend, just send this patch.
>
> > Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
> > ---
> >   drivers/fsi/fsi-core.c       | 41 ++++++++++++++++++++++--------------
> >   drivers/fsi/fsi-master-hub.c |  2 ++
> >   2 files changed, 27 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
> > index ec4d02264391..503061a6740b 100644
> > --- a/drivers/fsi/fsi-core.c
> > +++ b/drivers/fsi/fsi-core.c
> > @@ -1327,46 +1327,55 @@ static struct class fsi_master_class = {
> >   int fsi_master_register(struct fsi_master *master)
> >   {
> >          int rc;
> > -       struct device_node *np;
> >
> >          mutex_init(&master->scan_lock);
> > -       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
> > +
> > +       if (master->idx) {
> Why do we allocate a new idx if there's already one?


At this point, the master driver (aspeed, hub, i2cr, whatever) might 
just be requesting a certain index. It's not allocated yet, so it needs 
to be allocated so that we don't get overlap.


> > +               master->idx = ida_alloc_range(&master_ida, master->idx,
> > +                                             master->idx, GFP_KERNEL);
> If we can't get one in the range we want, we ask for any? Should this
> print a warning?


Perhaps, we could also return error here if we decide that the requested 
index is needed and not just wanted.


> > +               if (master->idx < 0)
> > +                       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
> > +       } else {
> If ixd was zero, we create one. This is the "normal" case?


Yes, the assumption is: zero is the default due to zero-alloc'd master 
structures.


> > +               master->idx = ida_alloc(&master_ida, GFP_KERNEL);
> > +       }
> > +
> We check the same error condition again.


Yes I might be able to make this cleaner...


> >          if (master->idx < 0)
> >                  return master->idx;
> > -       dev_set_name(&master->dev, "fsi%d", master->idx);
> > +       if (!dev_name(&master->dev))
> > +               dev_set_name(&master->dev, "fsi%d", master->idx);
> > +
> >          master->dev.class = &fsi_master_class;
> >
> > +       mutex_lock(&master->scan_lock);
> >          rc = device_register(&master->dev);
> >          if (rc) {
> >                  ida_free(&master_ida, master->idx);
> > -               return rc;
> > -       }
> > +       } else {
> > +               struct device_node *np = dev_of_node(&master->dev);
> This change looks a bit different to the idx changes. What's happening here?


This is just restructuring to get the lock before the scan. It could be 
a separate commit, yea.

Thanks for the review!

Eddie


> > -       np = dev_of_node(&master->dev);
> > -       if (!of_property_read_bool(np, "no-scan-on-init")) {
> > -               mutex_lock(&master->scan_lock);
> > -               fsi_master_scan(master);
> > -               mutex_unlock(&master->scan_lock);
> > +               if (!of_property_read_bool(np, "no-scan-on-init"))
> > +                       fsi_master_scan(master);
> >          }
> >
> > -       return 0;
> > +       mutex_unlock(&master->scan_lock);
> > +       return rc;
> >   }
> >   EXPORT_SYMBOL_GPL(fsi_master_register);
> >
> >   void fsi_master_unregister(struct fsi_master *master)
> >   {
> > -       trace_fsi_master_unregister(master);
> > +       int idx = master->idx;
> >
> > -       if (master->idx >= 0) {
> > -               ida_free(&master_ida, master->idx);
> > -               master->idx = -1;
> > -       }
> > +       trace_fsi_master_unregister(master);
> >
> >          mutex_lock(&master->scan_lock);
> >          fsi_master_unscan(master);
> > +       master->n_links = 0;
> >          mutex_unlock(&master->scan_lock);
> > +
> >          device_unregister(&master->dev);
> > +       ida_free(&master_ida, idx);
> >   }
> >   EXPORT_SYMBOL_GPL(fsi_master_unregister);
> >
> > diff --git a/drivers/fsi/fsi-master-hub.c b/drivers/fsi/fsi-master-hub.c
> > index 6d8b6e8854e5..36da643b3201 100644
> > --- a/drivers/fsi/fsi-master-hub.c
> > +++ b/drivers/fsi/fsi-master-hub.c
> > @@ -12,6 +12,7 @@
> >   #include <linux/slab.h>
> >
> >   #include "fsi-master.h"
> > +#include "fsi-slave.h"
> >
> >   #define FSI_ENGID_HUB_MASTER           0x1c
> >
> > @@ -229,6 +230,7 @@ static int hub_master_probe(struct device *dev)
> >          hub->master.dev.release = hub_master_release;
> >          hub->master.dev.of_node = of_node_get(dev_of_node(dev));
> >
> > +       hub->master.idx = fsi_dev->slave->link + 1;
> >          hub->master.n_links = links;
> >          hub->master.read = hub_master_read;
> >          hub->master.write = hub_master_write;
> > --
> > 2.31.1