Commit 6aa41144 authored by Dan Williams's avatar Dan Williams
Browse files

cxl/acpi: Add a host-bridge index lookup mechanism 



The ACPI CXL Fixed Memory Window Structure (CFMWS) defines multiple
methods to determine which host bridge provides access to a given
endpoint relative to that device's position in the interleave. The
"Interleave Arithmetic" defines either a "standard modulo" /
round-random algorithm, or "xormap" based algorithm which can be defined
as a non-linear transform. Given that there are already more options
beyond "standard modulo" and that "xormap" may turn out to be ACPI CXL
specific, provide a callback for the region provisioning code to map
endpoint positions back to expected host bridge id (cxl_dport target).

For now just support the simple modulo math case and save the xormap for
a follow-on change.

Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20220624041950.559155-14-dan.j.williams@intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent b9686e8c

drivers/cxl/core/port.c

+16 −0
Original line number Diff line number Diff line
@@ -1421,6 +1421,20 @@ static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd, 
	return rc;

}



static struct cxl_dport *cxl_hb_modulo(struct cxl_root_decoder *cxlrd, int pos)

{

	struct cxl_switch_decoder *cxlsd = &cxlrd->cxlsd;

	struct cxl_decoder *cxld = &cxlsd->cxld;

	int iw;



	iw = cxld->interleave_ways;

	if (dev_WARN_ONCE(&cxld->dev, iw != cxlsd->nr_targets,

			  "misconfigured root decoder\n"))

		return NULL;



	return cxlrd->cxlsd.target[pos % iw];

}



static struct lock_class_key cxl_decoder_key;



/**
@@ -1510,6 +1524,8 @@ struct cxl_root_decoder *cxl_root_decoder_alloc(struct cxl_port *port, 
		return ERR_PTR(rc);

	}



	cxlrd->calc_hb = cxl_hb_modulo;



	cxld = &cxlsd->cxld;

	cxld->dev.type = &cxl_decoder_root_type;

	/*

drivers/cxl/cxl.h

+2 −0
Original line number Diff line number Diff line
@@ -322,11 +322,13 @@ struct cxl_switch_decoder { 
 * struct cxl_root_decoder - Static platform CXL address decoder

 * @res: host / parent resource for region allocations

 * @region_id: region id for next region provisioning event

 * @calc_hb: which host bridge covers the n'th position by granularity

 * @cxlsd: base cxl switch decoder

 */

struct cxl_root_decoder {

	struct resource *res;

	atomic_t region_id;

	struct cxl_dport *(*calc_hb)(struct cxl_root_decoder *cxlrd, int pos);

	struct cxl_switch_decoder cxlsd;

};