[PATCH] interconnect: Aggregate bandwidth votes for unused nodes in sync_state()

[PATCH] interconnect: Aggregate bandwidth votes for unused nodes in sync_state()

[Odelu Kukatla]

When removing the initial bandwidth votes in sync_state(), make sure
to call the aggregate() function for nodes which don't have any
clients yet. aggregate_requests() does not invoke aggregate()
for unused nodes.

Signed-off-by: Odelu Kukatla <okukatla@codeaurora.org>
---
 drivers/interconnect/core.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
index 8a1e70e..1d9a00a 100644
--- a/drivers/interconnect/core.c
+++ b/drivers/interconnect/core.c
@@ -1106,7 +1106,16 @@ void icc_sync_state(struct device *dev)
 		dev_dbg(p->dev, "interconnect provider is in synced state\n");
 		list_for_each_entry(n, &p->nodes, node_list) {
 			if (n->init_avg || n->init_peak) {
-				aggregate_requests(n);
+				if (hlist_empty(&n->req_list)) {
+					if (p->pre_aggregate)
+						p->pre_aggregate(n);
+
+					p->aggregate(n, 0, 0, 0, &n->avg_bw,
+						&n->peak_bw);
+				} else {
+					aggregate_requests(n);
+				}
+
 				p->set(n, n);
 			}
 		}
-- 
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a Linux Foundation Collaborative Project

Re: [PATCH] interconnect: Aggregate bandwidth votes for unused nodes in sync_state()

[Matthias Kaehlcke]

On Sat, Jun 19, 2021 at 10:38:29PM +0530, Odelu Kukatla wrote:
> When removing the initial bandwidth votes in sync_state(), make sure
> to call the aggregate() function for nodes which don't have any
> clients yet. aggregate_requests() does not invoke aggregate()
> for unused nodes.
> 
> Signed-off-by: Odelu Kukatla <okukatla@codeaurora.org>

It seems this should have a 'Fixes' tag for b1d681d8d324 ("interconnect:
Add sync state support")', to make sure the change makes it into the
stable trees.

> ---
>  drivers/interconnect/core.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> index 8a1e70e..1d9a00a 100644
> --- a/drivers/interconnect/core.c
> +++ b/drivers/interconnect/core.c
> @@ -1106,7 +1106,16 @@ void icc_sync_state(struct device *dev)
>  		dev_dbg(p->dev, "interconnect provider is in synced state\n");
>  		list_for_each_entry(n, &p->nodes, node_list) {
>  			if (n->init_avg || n->init_peak) {
> -				aggregate_requests(n);
> +				if (hlist_empty(&n->req_list)) {

nit: consider handling the common case in the 'if' branch and the exception of
the initial votes in 'else'.

> +					if (p->pre_aggregate)
> +						p->pre_aggregate(n);
> +
> +					p->aggregate(n, 0, 0, 0, &n->avg_bw,
> +						&n->peak_bw);
> +				} else {
> +					aggregate_requests(n);
> +				}
> +
>  				p->set(n, n);
>  			}
>  		}

Re: [PATCH] interconnect: Aggregate bandwidth votes for unused nodes in sync_state()

[Mike Tipton]

On 6/19/2021 10:08 AM, Odelu Kukatla wrote:
> When removing the initial bandwidth votes in sync_state(), make sure
> to call the aggregate() function for nodes which don't have any
> clients yet. aggregate_requests() does not invoke aggregate()
> for unused nodes.
> 
> Signed-off-by: Odelu Kukatla <okukatla@codeaurora.org>
> ---
>   drivers/interconnect/core.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> index 8a1e70e..1d9a00a 100644
> --- a/drivers/interconnect/core.c
> +++ b/drivers/interconnect/core.c
> @@ -1106,7 +1106,16 @@ void icc_sync_state(struct device *dev)
>   		dev_dbg(p->dev, "interconnect provider is in synced state\n");
>   		list_for_each_entry(n, &p->nodes, node_list) {
>   			if (n->init_avg || n->init_peak) {
> -				aggregate_requests(n);
> +				if (hlist_empty(&n->req_list)) {
> +					if (p->pre_aggregate)
> +						p->pre_aggregate(n);
> +
> +					p->aggregate(n, 0, 0, 0, &n->avg_bw,
> +						&n->peak_bw);
> +				} else {
> +					aggregate_requests(n);
> +				}
> +
>   				p->set(n, n);
>   			}
>   		}
> 

I ran into this issue myself last week. There is an alternative fix that 
I think is a little cleaner. The reason we need the aggregate() call 
here is that the icc-rpmh providers only add BCMs to the commit list in 
the aggregate() callback. If aggregate() isn't called, then we don't 
commit anything to HW. But, if we instead add BCMs to the commit list in 
pre_aggregate(), then the existing aggregate_requests() call is 
sufficient, since that always calls pre_aggregate() even when req_list 
is empty. That means we'd need to update icc_node_add() to call 
pre_aggregate() before aggregate(), otherwise we wouldn't commit the 
initial floors. But I think always calling pre_aggregate() before 
aggregate() is a reasonable requirement.

I've posted these changes in a patch series along with a separate 
sync-state-related fix. The solutions could co-exist, but they are 
largely redundant.