[RFC 5/5] cxl: Avoid to create dax regions for type2 accelerators

[Huang Ying <ying.huang@intel.com>]

The memory range of a type2 accelerator should be managed by the type2
accelerator specific driver instead of the common dax region drivers,
as discussed in [1].

[1] https://lore.kernel.org/linux-cxl/66469ff1b8fbc_2c2629427@dwillia2-xfh.jf.intel.com.notmuch/

So, in this patch, we skip dax regions creation for type2 accelerator
device memory regions.

Based on: https://lore.kernel.org/linux-cxl/168592159835.1948938.1647215579839222774.stgit@dwillia2-xfh.jf.intel.com/

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Alejandro Lucero <alucerop@amd.com>
---
 drivers/cxl/core/region.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 9c68ec445128..b276752c38da 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3466,6 +3466,14 @@ static int cxl_region_probe(struct device *dev)
 					p->res->start, p->res->end, cxlr,
 					is_system_ram) > 0)
 			return 0;
+		/*
+		 * Accelerator regions have specific usage, skip
+		 * device-dax registration.
+		 */
+		if (cxlr->type == CXL_DECODER_ACCEL)
+			return 0;
+
+		/* Expander routes to device-dax */
 		return devm_cxl_add_dax_region(cxlr);
 	default:
 		dev_dbg(&cxlr->dev, "unsupported region mode: %d\n",
-- 
2.39.2