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Date: Thu, 9 Jul 2020 22:04:08 -0700
From: Mike Tipton <mdtipton@...eaurora.org>
To: Georgi Djakov <georgi.djakov@...aro.org>, linux-pm@...r.kernel.org
Cc: saravanak@...gle.com, okukatla@...eaurora.org,
bjorn.andersson@...aro.org, vincent.guittot@...aro.org,
linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] interconnect: Add sync state support
On 7/9/2020 4:07 AM, Georgi Djakov wrote:
> The bootloaders often do some initial configuration of the interconnects
> in the system and we want to keep this configuration until all consumers
> have probed and expressed their bandwidth needs. This is because we don't
> want to change the configuration by starting to disable unused paths until
> every user had a chance to request the amount of bandwidth it needs.
>
> To accomplish this we will implement an interconnect specific sync_state
> callback which will synchronize (aggregate and set) the current bandwidth
> settings when all consumers have been probed.
>
> Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>
> ---
> drivers/interconnect/core.c | 56 +++++++++++++++++++++++++++
> include/linux/interconnect-provider.h | 3 ++
> 2 files changed, 59 insertions(+)
>
> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> index e5f998744501..e53adfee1ee3 100644
> --- a/drivers/interconnect/core.c
> +++ b/drivers/interconnect/core.c
> @@ -26,6 +26,8 @@
>
> static DEFINE_IDR(icc_idr);
> static LIST_HEAD(icc_providers);
> +static int providers_count;
> +static bool synced_state;
> static DEFINE_MUTEX(icc_lock);
> static struct dentry *icc_debugfs_dir;
>
> @@ -255,6 +257,10 @@ static int aggregate_requests(struct icc_node *node)
> continue;
> p->aggregate(node, r->tag, r->avg_bw, r->peak_bw,
> &node->avg_bw, &node->peak_bw);
> +
> + /* during boot use the initial bandwidth as a floor value */
> + if (!synced_state)
> + node->peak_bw = max(node->peak_bw, node->init_bw);
> }
>
> return 0;
> @@ -919,6 +925,12 @@ void icc_node_add(struct icc_node *node, struct icc_provider *provider)
> node->provider = provider;
> list_add_tail(&node->node_list, &provider->nodes);
>
> + /* get the bandwidth value and sync it with the hardware */
> + if (node->init_bw && provider->set) {
> + node->peak_bw = node->init_bw;
> + provider->set(node, node);
> + }
> +
We'll need separate initial values for avg_bw/peak_bw. Some of our BCMs
only support one or the other. Voting for one it doesn't support is a
NOP. Additionally, some targets bring multiple subsystems out of reset
in bootloaders and in those cases we'd need BCM to sum our initial
avg_bw with the other subsystems.
> mutex_unlock(&icc_lock);
> }
> EXPORT_SYMBOL_GPL(icc_node_add);
> @@ -1014,8 +1026,52 @@ int icc_provider_del(struct icc_provider *provider)
> }
> EXPORT_SYMBOL_GPL(icc_provider_del);
>
> +static int of_count_icc_providers(struct device_node *np)
> +{
> + struct device_node *child;
> + int count = 0;
> +
> + for_each_available_child_of_node(np, child) {
> + if (of_property_read_bool(child, "#interconnect-cells"))
> + count++;
> + count += of_count_icc_providers(child);
> + }
> + of_node_put(np);
> +
> + return count;
> +}
> +
> +void icc_sync_state(struct device *dev)
> +{
> + struct icc_provider *p;
> + struct icc_node *n;
> + static int count;
> +
> + count++;
> +
> + if (count < providers_count)
> + return;
> +
> + mutex_lock(&icc_lock);
> + list_for_each_entry(p, &icc_providers, provider_list) {
> + dev_dbg(p->dev, "interconnect provider is in synced state\n");
> + list_for_each_entry(n, &p->nodes, node_list) {
> + aggregate_requests(n);
> + p->set(n, n);
We could skip re-aggregating/setting for nodes that don't specify an
initial BW. That'll save a lot of unnecessary HW voting. In practice,
we'll only need to specify an initial minimum BW for a small subset of
nodes (likely only one per-BCM we care about). Technically we only need
to re-aggregate/set if the current BW vote is limited by init_bw, but
that optimization is less important than skipping the majority that
don't have an init_bw.
> + }
> + }
> + mutex_unlock(&icc_lock);
> + synced_state = true;
> +}
> +EXPORT_SYMBOL_GPL(icc_sync_state);
> +
> static int __init icc_init(void)
> {
> + struct device_node *root = of_find_node_by_path("/");
> +
> + providers_count = of_count_icc_providers(root);
> + of_node_put(root);
> +
> icc_debugfs_dir = debugfs_create_dir("interconnect", NULL);
> debugfs_create_file("interconnect_summary", 0444,
> icc_debugfs_dir, NULL, &icc_summary_fops);
> diff --git a/include/linux/interconnect-provider.h b/include/linux/interconnect-provider.h
> index 0c494534b4d3..153fb7616f96 100644
> --- a/include/linux/interconnect-provider.h
> +++ b/include/linux/interconnect-provider.h
> @@ -71,6 +71,7 @@ struct icc_provider {
> * @req_list: a list of QoS constraint requests associated with this node
> * @avg_bw: aggregated value of average bandwidth requests from all consumers
> * @peak_bw: aggregated value of peak bandwidth requests from all consumers
> + * @init_bw: the bandwidth value that is read from the hardware during init
> * @data: pointer to private data
> */
> struct icc_node {
> @@ -87,6 +88,7 @@ struct icc_node {
> struct hlist_head req_list;
> u32 avg_bw;
> u32 peak_bw;
> + u32 init_bw;
> void *data;
> };
>
> @@ -103,6 +105,7 @@ void icc_node_del(struct icc_node *node);
> int icc_nodes_remove(struct icc_provider *provider);
> int icc_provider_add(struct icc_provider *provider);
> int icc_provider_del(struct icc_provider *provider);
> +void icc_sync_state(struct device *dev);
>
> #else
>
>
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