coresight: tmc: Enable SG capability on ACPI based SoC-400 TMC ETR devices

This detects and enables the scatter gather capability (SG) on ACPI based
Soc-400 TMC ETR devices via a new property called 'arm-armhc97c-sg-enable'.
The updated ACPI spec can be found below, which contains this new property.

https://developer.arm.com/documentation/den0067/latest/

This preserves current handling for the property 'arm,scatter-gather' both
on ACPI and DT based platforms i.e the presence of the property is checked
instead of the value.

Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20240404072934.940760-1-anshuman.khandual@arm.com

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
index 4b50d043ce0446261f2405a9f36c2f031734ecdc..741ce1748e759dcfd824ae23f48d1e9fd2330597 100644 (file)
--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
@@ -4,6 +4,7 @@
  * Description: CoreSight Trace Memory Controller driver
  */
 
+#include <linux/acpi.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/types.h>
@@ -362,7 +363,32 @@ static const struct attribute_group *coresight_etr_groups[] = {
 
 static inline bool tmc_etr_can_use_sg(struct device *dev)
 {
-       return fwnode_property_present(dev->fwnode, "arm,scatter-gather");
+       int ret;
+       u8 val_u8;
+
+       /*
+        * Presence of the property 'arm,scatter-gather' is checked
+        * on the platform for the feature support, rather than its
+        * value.
+        */
+       if (is_of_node(dev->fwnode)) {
+               return fwnode_property_present(dev->fwnode, "arm,scatter-gather");
+       } else if (is_acpi_device_node(dev->fwnode)) {
+               /*
+                * TMC_DEVID_NOSCAT test in tmc_etr_setup_caps(), has already ensured
+                * this property is only checked for Coresight SoC 400 TMC configured
+                * as ETR.
+                */
+               ret = fwnode_property_read_u8(dev->fwnode, "arm-armhc97c-sg-enable", &val_u8);
+               if (!ret)
+                       return !!val_u8;
+
+               if (fwnode_property_present(dev->fwnode, "arm,scatter-gather")) {
+                       pr_warn_once("Deprecated ACPI property - arm,scatter-gather\n");
+                       return true;
+               }
+       }
+       return false;
 }
 
 static inline bool tmc_etr_has_non_secure_access(struct tmc_drvdata *drvdata)