Re: [PATCH v10 1/7] interconnect: Add generic on-chip interconnect API

[Georgi Djakov]

Hi Joe,

On 11/27/18 20:35, Joe Perches wrote:
> On Tue, 2018-11-27 at 20:03 +0200, Georgi Djakov wrote:
> > This patch introduces a new API to get requirements and configure the
> > interconnect buses across the entire chipset to fit with the current
> > demand.
>
> trivial notes:
>
> > diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> []
> > +static int apply_constraints(struct icc_path *path)
> > +{
> > +	struct icc_node *next, *prev = NULL;
> > +	int ret = -EINVAL;
> > +	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;
> > +
> > +		/* set the constraints */
> > +		ret = p->set(prev, next);
> > +		if (ret)
> > +			goto out;
> > +	}
> > +out:
> > +	return ret;
> > +}
>
> The use of ", prev = next" appears somewhat tricky code.
> Perhaps move the assignment of prev to the bottom of the loop.
> Perhaps the temporary p assignment isn't useful either.
>
> > +int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw)
> > +{
> []
> > +	ret = apply_constraints(path);
> > +	if (ret)
> > +		pr_debug("interconnect: error applying constraints (%d)", ret);
>
> Ideally all pr_<foo> formats should end in '\n'
>
> > +static struct icc_node *icc_node_create_nolock(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;
>
> Generally, this code appears to overly rely on goto when
> direct returns could be more readable.
>
> > +	}
> > +
> > +	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
> > +	if (WARN(id < 0, "couldn't get idr")) {
>
> This seems to unnecessarily hide the id < 0 test in a WARN
>
> Why is this a WARN and not a simpler
> 	if (id < 0) {
> 		[ pr_err(...); or WARN(1, ...); ]
>
> > +		kfree(node);
> > +		node = ERR_PTR(id);
> > +		goto out;
> > +	}
> > +
> > +	node->id = id;
> > +
> > +out:
> > +	return node;
> > +}

Thank you for helping to improve the code. The above suggestions make it 
cleaner indeed.

> []
> > diff --git a/include/linux/interconnect.h b/include/linux/interconnect.h
> []
> > +/* macros for converting to icc units */
> > +#define bps_to_icc(x)	(1)
> > +#define kBps_to_icc(x)	(x)
> []
> > +#define MBps_to_icc(x)	(x * 1000)
> > +#define GBps_to_icc(x)	(x * 1000 * 1000)
> > +#define kbps_to_icc(x)	(x / 8 + ((x) % 8 ? 1 : 0))
> > +#define Mbps_to_icc(x)	(x * 1000 / 8 )
> > +#define Gbps_to_icc(x)	(x * 1000 * 1000 / 8)
>
> The last 5 macros should parenthesize x

Oops.. obviously i forgot to run checkpatch --strict. Will fix!

BR,
Georgi