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SubjectRe: [PATCH v10 1/7] interconnect: Add generic on-chip interconnect API
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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;
> +}
[]
> 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


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