[PATCH v4 01/14] cxl/region: Store root decoder in struct cxl_region

Robert Richter
2025-11-03T18:48:45Z

A region is always bound to a root decoder. The region's associated
root decoder is often needed. Add it to struct cxl_region.

This simplifies the code by removing dynamic lookups and the root
decoder argument from the function argument list where possible.

Patch is a prerequisite to implement address translation which uses
struct cxl_region to store all relevant region and interleaving
parameters. It changes the argument list of __construct_region() in
preparation of adding a context argument. Additionally the arg list of
cxl_region_attach_position() is simplified and the use of
to_cxl_root_decoder() removed, which always reconstructs and checks
the pointer. The pointer never changes and is frequently used. Code
becomes more readable as this amphazises the binding between both
objects.

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Signed-off-by: Robert Richter <rrichter@amd.com>
---
drivers/cxl/core/region.c | 37 +++++++++++++++++++------------------
drivers/cxl/cxl.h | 2 ++
2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index b06fee1978ba..45b1386a18d7 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -495,9 +495,9 @@ static ssize_t interleave_ways_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t len)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev->parent);
- struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
struct cxl_region *cxlr = to_cxl_region(dev);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
+ struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
struct cxl_region_params *p = &cxlr->params;
unsigned int val, save;
int rc;
@@ -558,9 +558,9 @@ static ssize_t interleave_granularity_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t len)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev->parent);
- struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
struct cxl_region *cxlr = to_cxl_region(dev);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
+ struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
struct cxl_region_params *p = &cxlr->params;
int rc, val;
u16 ig;
@@ -634,7 +634,7 @@ static DEVICE_ATTR_RO(mode);

static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
struct cxl_region_params *p = &cxlr->params;
struct resource *res;
u64 remainder = 0;
@@ -1327,7 +1327,7 @@ static int cxl_port_setup_targets(struct cxl_port *port,
struct cxl_region *cxlr,
struct cxl_endpoint_decoder *cxled)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
int parent_iw, parent_ig, ig, iw, rc, inc = 0, pos = cxled->pos;
struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
@@ -1686,10 +1686,10 @@ static int cxl_region_validate_position(struct cxl_region *cxlr,
}

static int cxl_region_attach_position(struct cxl_region *cxlr,
- struct cxl_root_decoder *cxlrd,
struct cxl_endpoint_decoder *cxled,
const struct cxl_dport *dport, int pos)
{
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
struct cxl_switch_decoder *cxlsd = &cxlrd->cxlsd;
struct cxl_decoder *cxld = &cxlsd->cxld;
@@ -1926,7 +1926,7 @@ static int cxl_region_sort_targets(struct cxl_region *cxlr)
static int cxl_region_attach(struct cxl_region *cxlr,
struct cxl_endpoint_decoder *cxled, int pos)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
struct cxl_dev_state *cxlds = cxlmd->cxlds;
struct cxl_region_params *p = &cxlr->params;
@@ -2031,8 +2031,7 @@ static int cxl_region_attach(struct cxl_region *cxlr,
ep_port = cxled_to_port(cxled);
dport = cxl_find_dport_by_dev(root_port,
ep_port->host_bridge);
- rc = cxl_region_attach_position(cxlr, cxlrd, cxled,
- dport, i);
+ rc = cxl_region_attach_position(cxlr, cxled, dport, i);
if (rc)
return rc;
}
@@ -2055,7 +2054,7 @@ static int cxl_region_attach(struct cxl_region *cxlr,
if (rc)
return rc;

- rc = cxl_region_attach_position(cxlr, cxlrd, cxled, dport, pos);
+ rc = cxl_region_attach_position(cxlr, cxled, dport, pos);
if (rc)
return rc;

@@ -2351,8 +2350,8 @@ static const struct attribute_group *region_groups[] = {

static void cxl_region_release(struct device *dev)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev->parent);
struct cxl_region *cxlr = to_cxl_region(dev);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
int id = atomic_read(&cxlrd->region_id);

/*
@@ -2435,10 +2434,12 @@ static struct cxl_region *cxl_region_alloc(struct cxl_root_decoder *cxlrd, int i
* region id allocations
*/
get_device(dev->parent);
+ cxlr->cxlrd = cxlrd;
+ cxlr->id = id;
+
device_set_pm_not_required(dev);
dev->bus = &cxl_bus_type;
dev->type = &cxl_region_type;
- cxlr->id = id;

return cxlr;
}
@@ -2937,7 +2938,7 @@ static bool has_spa_to_hpa(struct cxl_root_decoder *cxlrd)
u64 cxl_dpa_to_hpa(struct cxl_region *cxlr, const struct cxl_memdev *cxlmd,
u64 dpa)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
u64 dpa_offset, hpa_offset, bits_upper, mask_upper, hpa;
struct cxl_region_params *p = &cxlr->params;
struct cxl_endpoint_decoder *cxled = NULL;
@@ -3013,7 +3014,7 @@ static int region_offset_to_dpa_result(struct cxl_region *cxlr, u64 offset,
struct dpa_result *result)
{
struct cxl_region_params *p = &cxlr->params;
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
struct cxl_endpoint_decoder *cxled;
u64 hpa, hpa_offset, dpa_offset;
u64 bits_upper, bits_lower;
@@ -3404,7 +3405,7 @@ static int match_region_by_range(struct device *dev, const void *data)
static int cxl_extended_linear_cache_resize(struct cxl_region *cxlr,
struct resource *res)
{
- struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
struct cxl_region_params *p = &cxlr->params;
resource_size_t size = resource_size(res);
resource_size_t cache_size, start;
@@ -3440,9 +3441,9 @@ static int cxl_extended_linear_cache_resize(struct cxl_region *cxlr,
}

static int __construct_region(struct cxl_region *cxlr,
- struct cxl_root_decoder *cxlrd,
struct cxl_endpoint_decoder *cxled)
{
+ struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
struct range *hpa = &cxled->cxld.hpa_range;
struct cxl_region_params *p;
@@ -3534,7 +3535,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
return cxlr;
}

- rc = __construct_region(cxlr, cxlrd, cxled);
+ rc = __construct_region(cxlr, cxled);
if (rc) {
devm_release_action(port->uport_dev, unregister_region, cxlr);
return ERR_PTR(rc);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 231ddccf8977..19b8b62a1322 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -521,6 +521,7 @@ enum cxl_partition_mode {
* struct cxl_region - CXL region
* @dev: This region's device
* @id: This region's id. Id is globally unique across all regions
+ * @cxlrd: Region's root decoder
* @mode: Operational mode of the mapped capacity
* @type: Endpoint decoder target type
* @cxl_nvb: nvdimm bridge for coordinating @cxlr_pmem setup / shutdown
@@ -534,6 +535,7 @@ enum cxl_partition_mode {
struct cxl_region {
struct device dev;
int id;
+ struct cxl_root_decoder *cxlrd;
enum cxl_partition_mode mode;
enum cxl_decoder_type type;
struct cxl_nvdimm_bridge *cxl_nvb;
--
2.47.3