Re: [RFC PATCH 12/18] cxl/cache: Add CXL Cache ID Route Table mapping

["Cheatham, Benjamin" <benjamin.cheatham@amd.com>]

[snip]

>> +
>> +static int find_cache_id(struct cxl_cachedev *cxlcd)
> 
> get_cache_id()? since you are returning the id.
> 

Sure!

>> +{
>> +	struct cxl_cache_state *cstate = &cxlcd->cxlds->cstate;
>> +	u32 cap, count, entry, portn;
>> +	struct cxl_dport *dport;
>> +	struct cxl_port *port;
>> +	int id;
>> +
>> +	if (cstate->cache_id != CXL_CACHE_ID_NO_ID)
>> +		return cstate->cache_id;
>> +
>> +	dport = cxlcd->endpoint->parent_dport;
>> +	if (!dport)
>> +		return -ENODEV;
>> +	port = dport->port;
>> +
>> +	cap = readl(port->regs.cidrt + CXL_CACHE_IDRT_CAP_OFFSET);
>> +	count = FIELD_GET(CXL_CACHE_IDRT_CAP_CNT_MASK, cap);
>> +
>> +	for (id = 0; id < count; id++) {
>> +		entry = readl(port->regs.cidrt +
>> +			      CXL_CACHE_IDRT_TARGETN_OFFSET(id));
>> +		portn = FIELD_GET(CXL_CACHE_IDRT_TARGETN_PORT_MASK, entry);
>> +		if (portn != dport->port_id &&
>> +		    !(entry & CXL_CACHE_IDRT_TARGETN_VALID))
>> +			continue;
>> +
>> +		cstate->cache_id = id;
>> +		return 0;
>> +	}
>> +
>> +	id = ida_alloc(&cache_id_ida, GFP_KERNEL);
>> +	if (id < 0)
>> +		return id;
>> +
>> +	cstate->cache_id = id;
>> +	return devm_add_action_or_reset(&cxlcd->dev, free_cache_id, cstate);
>> +}
>> +
>> +static int devm_cxl_cachedev_allocate_cache_id(struct cxl_cachedev *cxlcd)
>> +{
>> +	struct cxl_port *endpoint = cxlcd->endpoint, *port;
>> +	struct cxl_dport *dport;
>> +	int rc;
>> +
>> +	for (dport = endpoint->parent_dport, port = parent_port_of(endpoint);
>> +	     dport && port && !is_cxl_root(port);
>> +	     dport = port->parent_dport, port = parent_port_of(port)) {
>> +		guard(device)(&port->dev);
>> +		rc = map_cache_idrt_cap(port);
> 
> Would it make sense to map this once at enumeration instead of every allocation?
> 

Yes. I ended up changing cache id assignment/programming to be part of the endpoint port probe
for cache devices. It makes more sense to do this there (imo) since it's technically a port capability
and not device dependent.