RE: [PATCH 6/9] bus: fsl-mc: dpio: add QBMan portal APIs for DPAA2

[Stuart Yoder]

> -----Original Message-----
> From: Ruxandra Ioana Radulescu
> Sent: Monday, November 28, 2016 12:10 PM
> To: Stuart Yoder <stuart.yoder@xxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx
> Cc: German Rivera <german.rivera@xxxxxxx>; devel@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> agraf@xxxxxxx; arnd@xxxxxxxx; Leo Li <leoyang.li@xxxxxxx>; Roy Pledge <roy.pledge@xxxxxxx>; Haiying Wang
> <haiying.wang@xxxxxxx>
> Subject: RE: [PATCH 6/9] bus: fsl-mc: dpio: add QBMan portal APIs for DPAA2
> 
> > -----Original Message-----
> > From: Stuart Yoder [mailto:stuart.yoder@xxxxxxx]
> > Sent: Friday, October 21, 2016 9:02 AM
> > To: gregkh@xxxxxxxxxxxxxxxxxxx
> > Cc: German Rivera <german.rivera@xxxxxxx>; devel@xxxxxxxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; agraf@xxxxxxx; arnd@xxxxxxxx; Leo Li
> > <leoyang.li@xxxxxxx>; Roy Pledge <roy.pledge@xxxxxxx>; Roy Pledge
> > <roy.pledge@xxxxxxx>; Haiying Wang <haiying.wang@xxxxxxx>; Stuart
> > Yoder <stuart.yoder@xxxxxxx>
> > Subject: [PATCH 6/9] bus: fsl-mc: dpio: add QBMan portal APIs for DPAA2
> >
> > From: Roy Pledge <Roy.Pledge@xxxxxxx>
> >
> > Add QBman APIs for frame queue and buffer pool operations.
> >
> > Signed-off-by: Roy Pledge <roy.pledge@xxxxxxx>
> > Signed-off-by: Haiying Wang <haiying.wang@xxxxxxx>
> > Signed-off-by: Stuart Yoder <stuart.yoder@xxxxxxx>
> > ---
> >  drivers/bus/fsl-mc/dpio/Makefile       |    2 +-
> >  drivers/bus/fsl-mc/dpio/qbman-portal.c | 1009
> > ++++++++++++++++++++++++++++++++
> >  drivers/bus/fsl-mc/dpio/qbman-portal.h |  464 +++++++++++++++
> >  3 files changed, 1474 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/bus/fsl-mc/dpio/qbman-portal.c
> >  create mode 100644 drivers/bus/fsl-mc/dpio/qbman-portal.h
> >
> > diff --git a/drivers/bus/fsl-mc/dpio/Makefile b/drivers/bus/fsl-
> > mc/dpio/Makefile
> > index 128befc..6588498 100644
> > --- a/drivers/bus/fsl-mc/dpio/Makefile
> > +++ b/drivers/bus/fsl-mc/dpio/Makefile
> > @@ -6,4 +6,4 @@ subdir-ccflags-y := -Werror
> >
> >  obj-$(CONFIG_FSL_MC_DPIO) += fsl-mc-dpio.o
> >
> > -fsl-mc-dpio-objs := dpio.o
> > +fsl-mc-dpio-objs := dpio.o qbman-portal.o
> > diff --git a/drivers/bus/fsl-mc/dpio/qbman-portal.c b/drivers/bus/fsl-
> > mc/dpio/qbman-portal.c
> > new file mode 100644
> > index 0000000..1eb3dd9
> > --- /dev/null
> > +++ b/drivers/bus/fsl-mc/dpio/qbman-portal.c
> 
> [...]
> 
> > +/**
> > + * qbman_swp_pull() - Issue the pull dequeue command
> > + * @s: the software portal object
> > + * @d: the software portal descriptor which has been configured with
> > + *     the set of qbman_pull_desc_set_*() calls
> > + *
> > + * Return 0 for success, and -EBUSY if the software portal is not ready
> > + * to do pull dequeue.
> > + */
> > +int qbman_swp_pull(struct qbman_swp *s, struct qbman_pull_desc *d)
> > +{
> > +	struct qbman_pull_desc *p;
> > +
> > +	if (!atomic_dec_and_test(&s->vdq.available)) {
> > +		atomic_inc(&s->vdq.available);
> > +		return -EBUSY;
> > +	}
> > +	s->vdq.storage = (void *)d->rsp_addr_virt;
> > +	d->tok = 1;
> > +	p = qbman_get_cmd(s, QBMAN_CENA_SWP_VDQCR);
> > +	*p = *d;
> > +	dma_wmb();
> > +
> > +	/* Set the verb byte, have to substitute in the valid-bit */
> > +	p->verb |= s->vdq.valid_bit;
> > +	s->vdq.valid_bit ^= QB_VALID_BIT;
> > +
> > +	return 0;
> > +}
> > +
> [...]
> > +
> > +/**
> > + * qbman_result_has_new_result() - Check and get the dequeue response
> > from the
> > + *                                 dq storage memory set in pull dequeue command
> > + * @s: the software portal object
> > + * @dq: the dequeue result read from the memory
> > + *
> > + * Return 1 for getting a valid dequeue result, or 0 for not getting a valid
> > + * dequeue result.
> > + *
> > + * Only used for user-provided storage of dequeue results, not DQRR. For
> > + * efficiency purposes, the driver will perform any required endianness
> > + * conversion to ensure that the user's dequeue result storage is in host-
> > endian
> > + * format. As such, once the user has called
> > qbman_result_has_new_result() and
> > + * been returned a valid dequeue result, they should not call it again on
> > + * the same memory location (except of course if another dequeue
> > command has
> > + * been executed to produce a new result to that location).
> > + */
> > +int qbman_result_has_new_result(struct qbman_swp *s, const struct
> > dpaa2_dq *dq)
> > +{
> > +	if (!dq->dq.tok)
> > +		return 0;
> 
> While testing the Ethernet driver I discovered that sometimes the above
> check fails.
> 
> When we check a store entry for the first time, if the hardware didn't
> manage to fill it with a valid respose yet, we may find a non-null value in the
> token field (because the stores have uninitialized memory). So by only
> checking that token is !=0, we risk processing an uninitialized memory area
> as a valid dequeue entry.
> 
> We should always compare the token field against 1, the value that is given
> to the hardware on the dequeue command. It might also be a good idea
> to use a define here, to make it clear 1 is a magic value.
> 
> And I think we should also zero the stores when they are first allocated,
> since even with the proposed fix there's still a (much smaller) risk of finding
> our exact token value in an uninitialized memory area.

Thanks.  Will fix this on v3 respin.

Stuart