cxl/port: Scan single-target ports for decoders

Do not assume that a single-target port falls back to a passthrough
decoder configuration. Scan for decoders and only fallback after probing
that the HDM decoder capability is not present.

One user visible affect of this bug is the inability to enumerate
present CXL regions as the decoder settings for the present decoders are
skipped.

Fixes: d17d0540a0db ("cxl/core/hdm: Add CXL standard decoder enumeration to the core")
Reported-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: http://lore.kernel.org/r/20230227153128.8164-1-Jonathan.Cameron@huawei.com
Cc: <stable@vger.kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://lore.kernel.org/r/168149845130.792294.3210421233937427962.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 6fdf7981ddc7b13f3ec39630403bf9c62cc3dfdb..abe3877cfa637114b4a3413974b9057719acb65c 100644 (file)
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -92,8 +92,9 @@ static int map_hdm_decoder_regs(struct cxl_port *port, void __iomem *crb,
 
        cxl_probe_component_regs(&port->dev, crb, &map.component_map);
        if (!map.component_map.hdm_decoder.valid) {
-               dev_err(&port->dev, "HDM decoder registers invalid\n");
-               return -ENXIO;
+               dev_dbg(&port->dev, "HDM decoder registers not implemented\n");
+               /* unique error code to indicate no HDM decoder capability */
+               return -ENODEV;
        }
 
        return cxl_map_component_regs(&port->dev, regs, &map,

diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
index 22a7ab2bae7c7e53878faf3b372718f50ea1457f..eb57324c4ad4a0e54c9a35500df9c3a216f603a2 100644 (file)
--- a/drivers/cxl/port.c
+++ b/drivers/cxl/port.c
@@ -66,14 +66,22 @@ static int cxl_switch_port_probe(struct cxl_port *port)
        if (rc < 0)
                return rc;
 
-       if (rc == 1)
-               return devm_cxl_add_passthrough_decoder(port);
-
        cxlhdm = devm_cxl_setup_hdm(port, NULL);
-       if (IS_ERR(cxlhdm))
+       if (!IS_ERR(cxlhdm))
+               return devm_cxl_enumerate_decoders(cxlhdm, NULL);
+
+       if (PTR_ERR(cxlhdm) != -ENODEV) {
+               dev_err(&port->dev, "Failed to map HDM decoder capability\n");
                return PTR_ERR(cxlhdm);
+       }
+
+       if (rc == 1) {
+               dev_dbg(&port->dev, "Fallback to passthrough decoder\n");
+               return devm_cxl_add_passthrough_decoder(port);
+       }
 
-       return devm_cxl_enumerate_decoders(cxlhdm, NULL);
+       dev_err(&port->dev, "HDM decoder capability not found\n");
+       return -ENXIO;
 }
 
 static int cxl_endpoint_port_probe(struct cxl_port *port)