cxl/hdm: Limit emulation to the number of range registers

Recall that range register emulation seeks to treat the 2 potential
range registers as Linux CXL "decoder" objects. The number of range
registers can be 1 or 2, while HDM decoder ranges can include more than
2.

Be careful not to confuse DVSEC range count with HDM capability decoder
count. Commit to range register earlier in devm_cxl_setup_hdm().
Otherwise, a device with more HDM decoders than range registers can set
@cxlhdm->decoder_count to an invalid value.

Avoid introducing a forward declaration by just moving the definition of
should_emulate_decoders() earlier in the file. should_emulate_decoders()
is unchanged.

Tested-by: Dave Jiang <dave.jiang@intel.com>
Fixes: d7a2153762c7 ("cxl/hdm: Add emulation when HDM decoders are not committed")
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/168012574932.221280.15944705098679646436.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 cc123996b1a47e5f4fd3977e888839714da52db9..9884b6d4d930ddec64d4ad312fc27f57606068fc 100644 (file)
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -101,6 +101,42 @@ static int map_hdm_decoder_regs(struct cxl_port *port, void __iomem *crb,
                                      BIT(CXL_CM_CAP_CAP_ID_HDM));
 }
 
+static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
+{
+       struct cxl_hdm *cxlhdm;
+       void __iomem *hdm;
+       u32 ctrl;
+       int i;
+
+       if (!info)
+               return false;
+
+       cxlhdm = dev_get_drvdata(&info->port->dev);
+       hdm = cxlhdm->regs.hdm_decoder;
+
+       if (!hdm)
+               return true;
+
+       /*
+        * If HDM decoders are present and the driver is in control of
+        * Mem_Enable skip DVSEC based emulation
+        */
+       if (!info->mem_enabled)
+               return false;
+
+       /*
+        * If any decoders are committed already, there should not be any
+        * emulated DVSEC decoders.
+        */
+       for (i = 0; i < cxlhdm->decoder_count; i++) {
+               ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(i));
+               if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl))
+                       return false;
+       }
+
+       return true;
+}
+
 /**
  * devm_cxl_setup_hdm - map HDM decoder component registers
  * @port: cxl_port to map
@@ -140,6 +176,16 @@ struct cxl_hdm *devm_cxl_setup_hdm(struct cxl_port *port,
                return ERR_PTR(-ENXIO);
        }
 
+       /*
+        * Now that the hdm capability is parsed, decide if range
+        * register emulation is needed and fixup cxlhdm accordingly.
+        */
+       if (should_emulate_decoders(info)) {
+               dev_dbg(dev, "Fallback map %d range register%s\n", info->ranges,
+                       info->ranges > 1 ? "s" : "");
+               cxlhdm->decoder_count = info->ranges;
+       }
+
        return cxlhdm;
 }
 EXPORT_SYMBOL_NS_GPL(devm_cxl_setup_hdm, CXL);
@@ -717,42 +763,6 @@ static int cxl_setup_hdm_decoder_from_dvsec(struct cxl_port *port,
        return 0;
 }
 
-static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
-{
-       struct cxl_hdm *cxlhdm;
-       void __iomem *hdm;
-       u32 ctrl;
-       int i;
-
-       if (!info)
-               return false;
-
-       cxlhdm = dev_get_drvdata(&info->port->dev);
-       hdm = cxlhdm->regs.hdm_decoder;
-
-       if (!hdm)
-               return true;
-
-       /*
-        * If HDM decoders are present and the driver is in control of
-        * Mem_Enable skip DVSEC based emulation
-        */
-       if (!info->mem_enabled)
-               return false;
-
-       /*
-        * If any decoders are committed already, there should not be any
-        * emulated DVSEC decoders.
-        */
-       for (i = 0; i < cxlhdm->decoder_count; i++) {
-               ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(i));
-               if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl))
-                       return false;
-       }
-
-       return true;
-}
-
 static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
                            int *target_map, void __iomem *hdm, int which,
                            u64 *dpa_base, struct cxl_endpoint_dvsec_info *info)