Re: [PATCH v2] interconnect: qcom: implement get_bw with rpmh_read

[Neil Armstrong]

On 9/8/26 16:39, Maulik Shah wrote:
> On 08-09-2026 13:39, Neil Armstrong wrote:
> > Since we can actually read back the APPS rpmh interconnect
> > BCM votes we can actually implement the get_bw() callback
> > and provide a coherent average and peak bandwidth at probe time.
> >
> > The benefits of that are:
> > - keep disabled BCMs disabled
> > - avoid voting unused BCMs to INT_MAX
> >
> > If the interconnects are correctly described for a platform,
> > all the required BCMs would be voted to the maximum bandwidth
> > until sync_state is reached.
> >
> > Since we only get the BCM vote, we need to redistribute
> > the vote values to the associated nodes. The initial BCM
> > votes are read back at probe time in order to be ready when
> > the get_bw() is called when a node is added.
> >
> > Tested-by: Georgi Djakov <djakov@xxxxxxxxxx> #db845c
> > Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> > ---
> > Changes in v2:
> > - Added tested-by
> > - Rebased on v7.3-rc1 now the rpmh_read() is merged
> > - Link to v1: https://patch.msgid.link/20251106-topic-sm8x50-icc-read-rpmh-v1-1-d03a2e5ca5f7@xxxxxxxxxx
> > ---
> >   drivers/interconnect/qcom/bcm-voter.c | 36 +++++++++++++++++++++
> >   drivers/interconnect/qcom/bcm-voter.h |  1 +
> >   drivers/interconnect/qcom/icc-rpmh.c  | 60 ++++++++++++++++++++++++++++++++++-
> >   3 files changed, 96 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/interconnect/qcom/bcm-voter.c b/drivers/interconnect/qcom/bcm-voter.c
> > index a2d437a05a11..9014bf20adad 100644
> > --- a/drivers/interconnect/qcom/bcm-voter.c
> > +++ b/drivers/interconnect/qcom/bcm-voter.c
> > @@ -261,6 +261,42 @@ void qcom_icc_bcm_voter_add(struct bcm_voter *voter, struct qcom_icc_bcm *bcm)
> >   }
> >   EXPORT_SYMBOL_GPL(qcom_icc_bcm_voter_add);
> >   
> > +/**
> > + * qcom_icc_bcm_get_bw - get current bcm vote
> > + * @voter: voter used to query bcm
> > + * @bcm: bcm to get current vote from
> > + */
> > +void qcom_icc_bcm_get_bw(struct bcm_voter *voter,
> > +			 struct qcom_icc_bcm *bcm)
> > +{
> > +	struct tcs_cmd cmd = { .addr = bcm->addr };
> > +	int ret, i;
> > +	u64 x, y;
> > +
> > +	mutex_lock(&voter->lock);
> > +
> > +	rpmh_invalidate(voter->dev);
>
> Don't see why rpmh_invalidate() is needed before a read request.

You're right, will drop.

Thanks,
Neil

> Thanks,
> Maulik
>
> > +
> > +	ret = rpmh_read(voter->dev, &cmd);
> > +	if (ret) {
> > +		pr_err("Error sending AMC RPMH requests (%d)\n", ret);
> > +		goto out;
> > +	}
> > +