Re: [PATCH v2 08/22] soc/fsl/qbman_portals: add APIs to retrieve the probing status

[Robin Murphy]

On 2018-10-03 11:50 AM, Laurentiu Tudor wrote:
> Hi Leo,
>
> On 27.09.2018 23:03, Li Yang wrote:
> > On Wed, Sep 26, 2018 at 8:26 AM <laurentiu.tudor@xxxxxxx> wrote:
> > > From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> > >
> > > Add a couple of new APIs to check the probing status of the required
> > > cpu bound qman and bman portals:
> > >    'int bman_portals_probed()' and 'int qman_portals_probed()'.
> > > They return the following values.
> > >    *  1 if qman/bman portals were all probed correctly
> > >    *  0 if qman/bman portals were not yet probed
> > >    * -1 if probing of qman/bman portals failed
> > > Drivers that use qman/bman portal driver services are required to use
> > > these APIs before calling any functions exported by these drivers or
> > > otherwise they will crash the kernel.
> > > First user will be the dpaa1 ethernet driver, coming in a subsequent
> > > patch.
> > >
> > > Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> > > ---
> > >    drivers/soc/fsl/qbman/bman_portal.c | 10 ++++++++++
> > >    drivers/soc/fsl/qbman/qman_portal.c | 10 ++++++++++
> > >    include/soc/fsl/bman.h              |  8 ++++++++
> > >    include/soc/fsl/qman.h              |  9 +++++++++
> > >    4 files changed, 37 insertions(+)
> > >
> > > diff --git a/drivers/soc/fsl/qbman/bman_portal.c b/drivers/soc/fsl/qbman/bman_portal.c
> > > index f9edd28894fd..8048d35de8a2 100644
> > > --- a/drivers/soc/fsl/qbman/bman_portal.c
> > > +++ b/drivers/soc/fsl/qbman/bman_portal.c
> > > @@ -32,6 +32,7 @@
> > >
> > >    static struct bman_portal *affine_bportals[NR_CPUS];
> > >    static struct cpumask portal_cpus;
> > > +static int __bman_portals_probed;
> > >    /* protect bman global registers and global data shared among portals */
> > >    static DEFINE_SPINLOCK(bman_lock);
> > >
> > > @@ -85,6 +86,12 @@ static int bman_online_cpu(unsigned int cpu)
> > >           return 0;
> > >    }
> > >
> > > +int bman_portals_probed(void)
> > > +{
> > > +       return __bman_portals_probed;
> > > +}
> > > +EXPORT_SYMBOL_GPL(bman_portals_probed);
> > > +
> > >    static int bman_portal_probe(struct platform_device *pdev)
> > >    {
> > >           struct device *dev = &pdev->dev;
> > > @@ -148,6 +155,7 @@ static int bman_portal_probe(struct platform_device *pdev)
> > >           spin_lock(&bman_lock);
> > >           cpu = cpumask_next_zero(-1, &portal_cpus);
> > >           if (cpu >= nr_cpu_ids) {
> > > +               __bman_portals_probed = 1;
> >
> > What if the last CPU is not used for portals?  Is there a hard
> > requirement that all CPUs need to be used for portal?
>
> As far as I know, in the current driver design a portal is required for
> each CPU.
>
> > What happens if the last CPU is offline?
>
> Can this happen at probe time?

As I understand things, yes - if you boot with "maxcpus=1", only the 
boot CPU will be onlined by the kernel, but the others can still be 
brought up manually by userspace later.

Robin.

> Anyway, I'm not sure that the driver is even aware of cpu hotplug but
> I'll let Roy comment on this one.
>
> > >                   /* unassigned portal, skip init */
> > >                   spin_unlock(&bman_lock);
> > >                   return 0;
> > > @@ -173,6 +181,8 @@ static int bman_portal_probe(struct platform_device *pdev)
> > >    err_ioremap2:
> > >           memunmap(pcfg->addr_virt_ce);
> > >    err_ioremap1:
> > > +        __bman_portals_probed = 1;
> > > +
> >
> > There are other error paths that not covered.
>
> Right, thanks for pointing. On top of that, the assigned value here
> should be -1 to signal error (instead of 1 which signals success).
>
> ---
> Best Regards, Laurentiu