linux-kernel - Re: [PATCH v5 1/8] interconnect: Add generic on-chip interconnect API

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Date:   Sun, 1 Jul 2018 14:06:21 +0300
From:   Georgi Djakov <georgi.djakov@...aro.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     linux-pm@...r.kernel.org, gregkh@...uxfoundation.org,
        rjw@...ysocki.net, robh+dt@...nel.org, mturquette@...libre.com,
        khilman@...libre.com, vincent.guittot@...aro.org,
        skannan@...eaurora.org, bjorn.andersson@...aro.org,
        amit.kucheria@...aro.org, seansw@....qualcomm.com,
        daidavid1@...eaurora.org, evgreen@...omium.org,
        mark.rutland@....com, lorenzo.pieralisi@....com,
        abailon@...libre.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v5 1/8] interconnect: Add generic on-chip interconnect API

Hi Matthias,

Thanks for reviewing!

On 06/27/2018 02:34 AM, Matthias Kaehlcke wrote:
> Hi Georgi,
> 
> On Wed, Jun 20, 2018 at 03:11:34PM +0300, Georgi Djakov wrote:
>> This patch introduce a new API to get requirements and configure the
> 
> nit: s/introduce/introduces/

Thanks!

[..]

>> +	if (found) {
>> +		struct icc_path *path = path_allocate(dst, depth);
>> +
>> +		if (IS_ERR(path))
>> +			return path;
>> +
>> +		/* initialize the path */
>> +		for (i = 0; i < path->num_nodes; i++) {
>> +			node = path->reqs[i].node;
>> +			path->reqs[i].dev = dev;
>> +			node->provider->users++;
> 
> nit: doing the assignment of path->reqs[i].dev before assiging 'node'
> or after incrementing the 'users' would slightly improve readability.

Ok, will re-factor this a bit.

>> +static int apply_constraints(struct icc_path *path)
>> +{
>> +	struct icc_node *next, *prev = NULL;
>> +	int ret = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < path->num_nodes; i++, prev = next) {
>> +		struct icc_provider *p;
>> +
>> +		next = path->reqs[i].node;
>> +		/*
>> +		 * Both endpoints should be valid master-slave pairs of the
>> +		 * same interconnect provider that will be configured.
>> +		 */
>> +		if (!prev || next->provider != prev->provider)
>> +			continue;
>> +
>> +		p = next->provider;
>> +
>> +		aggregate_provider(p);
>> +
>> +		if (p->set) {
>> +			/* set the constraints */
>> +			ret = p->set(prev, next, p->avg_bw, p->peak_bw);
>> +		}
> 
> remove curly brackets
> 
> EDIT: actually the condition can be removed, icc_provider_add() fails
> when p->set is NULL.

Agree!

> 
>> +int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw)
>> +{
>> +	struct icc_node *node;
>> +	struct icc_provider *p;
>> +	size_t i;
>> +	int ret = 0;
> 
> initialization is not necessary
> 

Ok.

>> +struct icc_path *icc_get(struct device *dev, const int src_id, const int dst_id)
>> +{
>> +	struct icc_node *src, *dst;
>> +	struct icc_path *path = ERR_PTR(-EPROBE_DEFER);
>> +
>> +	src = node_find(src_id);
>> +	if (!src) {
>> +		dev_err(dev, "%s: invalid src=%d\n", __func__, src_id);
>> +		goto out;
>> +	}
>> +
>> +	dst = node_find(dst_id);
>> +	if (!dst) {
>> +		dev_err(dev, "%s: invalid dst=%d\n", __func__, dst_id);
>> +		goto out;
>> +	}
>> +
>> +	mutex_lock(&icc_lock);
>> +	path = path_find(dev, src, dst);
>> +	mutex_unlock(&icc_lock);
>> +	if (IS_ERR(path)) {
>> +		dev_err(dev, "%s: invalid path=%ld\n", __func__, PTR_ERR(path));
>> +		goto out;
> 
> this goto isn't really needed

Ok.

>> +struct icc_node *icc_node_create(int id)
>> +{
>> +	struct icc_node *node;
>> +
>> +	/* check if node already exists */
>> +	node = node_find(id);
>> +	if (node)
>> +		goto out;
>> +
>> +	node = kzalloc(sizeof(*node), GFP_KERNEL);
>> +	if (!node) {
>> +		node = ERR_PTR(-ENOMEM);
>> +		goto out;
>> +	}
>> +
>> +	mutex_lock(&icc_lock);
>> +
>> +	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
>> +	if (WARN(id < 0, "couldn't get idr")) {
> 
> kfree(node);

Thanks!

>> +int icc_node_add(struct icc_node *node, struct icc_provider *provider)
>> +{
>> +	mutex_lock(&icc_lock);
>> +
>> +	node->provider = provider;
>> +	list_add(&node->node_list, &provider->nodes);
>> +
>> +	mutex_unlock(&icc_lock);
>> +
>> +	return 0;
>> +}
> 
> The function returns always 0. Should probably be void so callers
> don't add pointless checks of the return value.

Agree, will change it!

>> +int icc_provider_add(struct icc_provider *provider)
>> +{
>> +	if (WARN_ON(!provider->set))
>> +		return -EINVAL;
>> +
>> +	mutex_init(&icc_lock);
> 
> Shouldn't this be mutex_lock()?

Yes, right!

>> +int icc_provider_del(struct icc_provider *provider)
>> +{
>> +	mutex_lock(&icc_lock);
>> +	if (provider->users) {
>> +		pr_warn("interconnect provider still has %d users\n",
>> +			provider->users);
>> +		mutex_unlock(&icc_lock);
>> +		return -EBUSY;
>> +	}
>> +
>> +	if (!list_empty_careful(&provider->nodes)) {
>> +		pr_warn("interconnect provider still has nodes\n");
>> +		mutex_unlock(&icc_lock);
>> +		return -EEXIST;
>> +	}
> 
> Could this be just list_empty()? If I didn't miss something icc_lock
> is held in all paths that change p->nodes (assuming that all changes
> should be done through the interfaces in this file).

It could be. Will update it. I just always want to be careful!

> Actually this check will always fail if icc_node_add() was called for
> this provider, it doesn't seem nodes are ever removed.
> 

The provider driver is responsible for the node removal.

Thanks,
Georgi