cxl/region: check interleave capability

Since interleave capability is not verified, if the interleave
capability of a target does not match the region need, committing decoder
should have failed at the device end.

In order to checkout this error as quickly as possible, driver needs
to check the interleave capability of target during attaching it to
region.

Per CXL specification r3.1(8.2.4.20.1 CXL HDM Decoder Capability Register),
bits 11 and 12 indicate the capability to establish interleaving in 3, 6,
12 and 16 ways. If these bits are not set, the target cannot be attached to
a region utilizing such interleave ways.

Additionally, bits 8 and 9 represent the capability of the bits used for
interleaving in the address, Linux tracks this in the cxl_port
interleave_mask.

Per CXL specification r3.1(8.2.4.20.13 Decoder Protection):
  eIW means encoded Interleave Ways.
  eIG means encoded Interleave Granularity.

  in HPA:
  if eIW is 0 or 8 (interleave ways: 1, 3), all the bits of HPA are used,
  the interleave bits are none, the following check is ignored.

  if eIW is less than 8 (interleave ways: 2, 4, 8, 16), the interleave bits
  start at bit position eIG + 8 and end at eIG + eIW + 8 - 1.

  if eIW is greater than 8 (interleave ways: 6, 12), the interleave bits
  start at bit position eIG + 8 and end at eIG + eIW - 1.

  if the interleave mask is insufficient to cover the required interleave
  bits, the target cannot be attached to the region.

Fixes: 384e624bb211 ("cxl/region: Attach endpoint decoders")
Signed-off-by: Yao Xingtao <yaoxt.fnst@fujitsu.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://patch.msgid.link/20240614084755.59503-2-yaoxt.fnst@fujitsu.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

2 files changed, 95 insertions, 0 deletions

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 784843fa2a22..3df10517a327 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -52,6 +52,14 @@ int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
 	struct cxl_dport *dport = NULL;
 	int single_port_map[1];
 	unsigned long index;
+	struct cxl_hdm *cxlhdm = dev_get_drvdata(&port->dev);
+
+	/*
+	 * Capability checks are moot for passthrough decoders, support
+	 * any and all possibilities.
+	 */
+	cxlhdm->interleave_mask = ~0U;
+	cxlhdm->iw_cap_mask = ~0UL;
 
 	cxlsd = cxl_switch_decoder_alloc(port, 1);
 	if (IS_ERR(cxlsd))
@@ -79,6 +87,11 @@ static void parse_hdm_decoder_caps(struct cxl_hdm *cxlhdm)
 		cxlhdm->interleave_mask |= GENMASK(11, 8);
 	if (FIELD_GET(CXL_HDM_DECODER_INTERLEAVE_14_12, hdm_cap))
 		cxlhdm->interleave_mask |= GENMASK(14, 12);
+	cxlhdm->iw_cap_mask = BIT(1) | BIT(2) | BIT(4) | BIT(8);
+	if (FIELD_GET(CXL_HDM_DECODER_INTERLEAVE_3_6_12_WAY, hdm_cap))
+		cxlhdm->iw_cap_mask |= BIT(3) | BIT(6) | BIT(12);
+	if (FIELD_GET(CXL_HDM_DECODER_INTERLEAVE_16_WAY, hdm_cap))
+		cxlhdm->iw_cap_mask |= BIT(16);
 }
 
 static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index aa24db608c33..538ebd5a64fd 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1101,6 +1101,26 @@ static int cxl_port_attach_region(struct cxl_port *port,
 	}
 	cxld = cxl_rr->decoder;
 
+	/*
+	 * the number of targets should not exceed the target_count
+	 * of the decoder
+	 */
+	if (is_switch_decoder(&cxld->dev)) {
+		struct cxl_switch_decoder *cxlsd;
+
+		cxlsd = to_cxl_switch_decoder(&cxld->dev);
+		if (cxl_rr->nr_targets > cxlsd->nr_targets) {
+			dev_dbg(&cxlr->dev,
+				"%s:%s %s add: %s:%s @ %d overflows targets: %d\n",
+				dev_name(port->uport_dev), dev_name(&port->dev),
+				dev_name(&cxld->dev), dev_name(&cxlmd->dev),
+				dev_name(&cxled->cxld.dev), pos,
+				cxlsd->nr_targets);
+			rc = -ENXIO;
+			goto out_erase;
+		}
+	}
+
 	rc = cxl_rr_ep_add(cxl_rr, cxled);
 	if (rc) {
 		dev_dbg(&cxlr->dev,
@@ -1210,6 +1230,50 @@ static int check_last_peer(struct cxl_endpoint_decoder *cxled,
 	return 0;
 }
 
+static int check_interleave_cap(struct cxl_decoder *cxld, int iw, int ig)
+{
+	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
+	struct cxl_hdm *cxlhdm = dev_get_drvdata(&port->dev);
+	unsigned int interleave_mask;
+	u8 eiw;
+	u16 eig;
+	int high_pos, low_pos;
+
+	if (!test_bit(iw, &cxlhdm->iw_cap_mask))
+		return -ENXIO;
+	/*
+	 * Per CXL specification r3.1(8.2.4.20.13 Decoder Protection),
+	 * if eiw < 8:
+	 *   DPAOFFSET[51: eig + 8] = HPAOFFSET[51: eig + 8 + eiw]
+	 *   DPAOFFSET[eig + 7: 0]  = HPAOFFSET[eig + 7: 0]
+	 *
+	 *   when the eiw is 0, all the bits of HPAOFFSET[51: 0] are used, the
+	 *   interleave bits are none.
+	 *
+	 * if eiw >= 8:
+	 *   DPAOFFSET[51: eig + 8] = HPAOFFSET[51: eig + eiw] / 3
+	 *   DPAOFFSET[eig + 7: 0]  = HPAOFFSET[eig + 7: 0]
+	 *
+	 *   when the eiw is 8, all the bits of HPAOFFSET[51: 0] are used, the
+	 *   interleave bits are none.
+	 */
+	ways_to_eiw(iw, &eiw);
+	if (eiw == 0 || eiw == 8)
+		return 0;
+
+	granularity_to_eig(ig, &eig);
+	if (eiw > 8)
+		high_pos = eiw + eig - 1;
+	else
+		high_pos = eiw + eig + 7;
+	low_pos = eig + 8;
+	interleave_mask = GENMASK(high_pos, low_pos);
+	if (interleave_mask & ~cxlhdm->interleave_mask)
+		return -ENXIO;
+
+	return 0;
+}
+
 static int cxl_port_setup_targets(struct cxl_port *port,
 				  struct cxl_region *cxlr,
 				  struct cxl_endpoint_decoder *cxled)
@@ -1360,6 +1424,15 @@ static int cxl_port_setup_targets(struct cxl_port *port,
 			return -ENXIO;
 		}
 	} else {
+		rc = check_interleave_cap(cxld, iw, ig);
+		if (rc) {
+			dev_dbg(&cxlr->dev,
+				"%s:%s iw: %d ig: %d is not supported\n",
+				dev_name(port->uport_dev),
+				dev_name(&port->dev), iw, ig);
+			return rc;
+		}
+
 		cxld->interleave_ways = iw;
 		cxld->interleave_granularity = ig;
 		cxld->hpa_range = (struct range) {
@@ -1796,6 +1869,15 @@ static int cxl_region_attach(struct cxl_region *cxlr,
 	struct cxl_dport *dport;
 	int rc = -ENXIO;
 
+	rc = check_interleave_cap(&cxled->cxld, p->interleave_ways,
+				  p->interleave_granularity);
+	if (rc) {
+		dev_dbg(&cxlr->dev, "%s iw: %d ig: %d is not supported\n",
+			dev_name(&cxled->cxld.dev), p->interleave_ways,
+			p->interleave_granularity);
+		return rc;
+	}
+
 	if (cxled->mode != cxlr->mode) {
 		dev_dbg(&cxlr->dev, "%s region mode: %d mismatch: %d\n",
 			dev_name(&cxled->cxld.dev), cxlr->mode, cxled->mode);