dmaengine: idxd: add configuration for concurrent work descriptor processing

Add sysfs knob to allow control of the number of work descriptors that can
be concurrently processed by an engine in the group as a fraction of the
Maximum Work Descriptors in Progress value specified in ENGCAP register.
This control knob is part of toggle for QoS control.
Signed-off-by: NDave Jiang <dave.jiang@intel.com>
Co-developed-by: NFenghua Yu <fenghua.yu@intel.com>
Signed-off-by: NFenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/r/20220917161222.2835172-5-fenghua.yu@intel.comSigned-off-by: NVinod Koul <vkoul@kernel.org>

Documentation/ABI/stable/sysfs-driver-dma-idxd

@@ -266,3 +266,15 @@ Contact:	dmaengine@vger.kernel.org
 Description:	Indicates the number of Read Buffers reserved for the use of
 		engines in the group. See DSA spec v1.2 9.2.18 GRPCFG Read Buffers
 		Reserved.
+
+What:		/sys/bus/dsa/devices/group<m>.<n>/desc_progress_limit
+Date:		Sept 14, 2022
+KernelVersion:	6.0.0
+Contact:	dmaengine@vger.kernel.org
+Description:	Allows control of the number of work descriptors that can be
+		concurrently processed by an engine in the group as a fraction
+		of the Maximum Work Descriptors in Progress value specified in
+		the ENGCAP register. The acceptable values are 0 (default),
+		1 (1/2 of max value), 2 (1/4 of the max value), and 3 (1/8 of
+		the max value). It's visible only on platforms that support
+		the capability.

drivers/dma/idxd/device.c

@@ -709,6 +709,7 @@ static void idxd_groups_clear_state(struct idxd_device *idxd)
 			group->tc_a = -1;
 			group->tc_b = -1;
 		}
+		group->desc_progress_limit = 0;
 	}
 }
 
@@ -765,10 +766,10 @@ static void idxd_group_config_write(struct idxd_group *group)
 
 	/* setup GRPFLAGS */
 	grpcfg_offset = GRPFLGCFG_OFFSET(idxd, group->id);
-	iowrite32(group->grpcfg.flags.bits, idxd->reg_base + grpcfg_offset);
-	dev_dbg(dev, "GRPFLAGS flags[%d: %#x]: %#x\n",
+	iowrite64(group->grpcfg.flags.bits, idxd->reg_base + grpcfg_offset);
+	dev_dbg(dev, "GRPFLAGS flags[%d: %#x]: %#llx\n",
 		group->id, grpcfg_offset,
-		ioread32(idxd->reg_base + grpcfg_offset));
+		ioread64(idxd->reg_base + grpcfg_offset));
 }
 
 static int idxd_groups_config_write(struct idxd_device *idxd)
@@ -929,6 +930,8 @@ static void idxd_group_flags_setup(struct idxd_device *idxd)
 			group->grpcfg.flags.rdbufs_allowed = group->rdbufs_allowed;
 		else
 			group->grpcfg.flags.rdbufs_allowed = idxd->max_rdbufs;
+
+		group->grpcfg.flags.desc_progress_limit = group->desc_progress_limit;
 	}
 }
 
@@ -1111,8 +1114,8 @@ static void idxd_group_load_config(struct idxd_group *group)
 	}
 
 	grpcfg_offset = GRPFLGCFG_OFFSET(idxd, group->id);
-	group->grpcfg.flags.bits = ioread32(idxd->reg_base + grpcfg_offset);
-	dev_dbg(dev, "GRPFLAGS flags[%d: %#x]: %#x\n",
+	group->grpcfg.flags.bits = ioread64(idxd->reg_base + grpcfg_offset);
+	dev_dbg(dev, "GRPFLAGS flags[%d: %#x]: %#llx\n",
 		group->id, grpcfg_offset, group->grpcfg.flags.bits);
 }
 

drivers/dma/idxd/idxd.h

@@ -96,6 +96,7 @@ struct idxd_group {
 	u8 rdbufs_reserved;
 	int tc_a;
 	int tc_b;
+	int desc_progress_limit;
 };
 
 struct idxd_pmu {

drivers/dma/idxd/registers.h

@@ -68,7 +68,8 @@ union group_cap_reg {
 		u64 total_rdbufs:8;	/* formerly total_tokens */
 		u64 rdbuf_ctrl:1;	/* formerly token_en */
 		u64 rdbuf_limit:1;	/* formerly token_limit */
-		u64 rsvd:46;
+		u64 progress_limit:1;	/* descriptor and batch descriptor */
+		u64 rsvd:45;
 	};
 	u64 bits;
 } __packed;
@@ -288,16 +289,18 @@ union msix_perm {
 
 union group_flags {
 	struct {
-		u32 tc_a:3;
-		u32 tc_b:3;
-		u32 rsvd:1;
-		u32 use_rdbuf_limit:1;
-		u32 rdbufs_reserved:8;
-		u32 rsvd2:4;
-		u32 rdbufs_allowed:8;
-		u32 rsvd3:4;
+		u64 tc_a:3;
+		u64 tc_b:3;
+		u64 rsvd:1;
+		u64 use_rdbuf_limit:1;
+		u64 rdbufs_reserved:8;
+		u64 rsvd2:4;
+		u64 rdbufs_allowed:8;
+		u64 rsvd3:4;
+		u64 desc_progress_limit:2;
+		u64 rsvd4:30;
 	};
-	u32 bits;
+	u64 bits;
 } __packed;
 
 struct grpcfg {

drivers/dma/idxd/sysfs.c

@@ -443,6 +443,37 @@ static struct device_attribute dev_attr_group_traffic_class_b =
 		__ATTR(traffic_class_b, 0644, group_traffic_class_b_show,
 		       group_traffic_class_b_store);
 
+static ssize_t group_desc_progress_limit_show(struct device *dev,
+					      struct device_attribute *attr,
+					      char *buf)
+{
+	struct idxd_group *group = confdev_to_group(dev);
+
+	return sysfs_emit(buf, "%d\n", group->desc_progress_limit);
+}
+
+static ssize_t group_desc_progress_limit_store(struct device *dev,
+					       struct device_attribute *attr,
+					       const char *buf, size_t count)
+{
+	struct idxd_group *group = confdev_to_group(dev);
+	int val, rc;
+
+	rc = kstrtoint(buf, 10, &val);
+	if (rc < 0)
+		return -EINVAL;
+
+	if (val & ~GENMASK(1, 0))
+		return -EINVAL;
+
+	group->desc_progress_limit = val;
+	return count;
+}
+
+static struct device_attribute dev_attr_group_desc_progress_limit =
+		__ATTR(desc_progress_limit, 0644, group_desc_progress_limit_show,
+		       group_desc_progress_limit_store);
+
 static struct attribute *idxd_group_attributes[] = {
 	&dev_attr_group_work_queues.attr,
 	&dev_attr_group_engines.attr,
@@ -454,11 +485,33 @@ static struct attribute *idxd_group_attributes[] = {
 	&dev_attr_group_read_buffers_reserved.attr,
 	&dev_attr_group_traffic_class_a.attr,
 	&dev_attr_group_traffic_class_b.attr,
+	&dev_attr_group_desc_progress_limit.attr,
 	NULL,
 };
 
+static bool idxd_group_attr_progress_limit_invisible(struct attribute *attr,
+						     struct idxd_device *idxd)
+{
+	return attr == &dev_attr_group_desc_progress_limit.attr &&
+	       !idxd->hw.group_cap.progress_limit;
+}
+
+static umode_t idxd_group_attr_visible(struct kobject *kobj,
+				       struct attribute *attr, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct idxd_group *group = confdev_to_group(dev);
+	struct idxd_device *idxd = group->idxd;
+
+	if (idxd_group_attr_progress_limit_invisible(attr, idxd))
+		return 0;
+
+	return attr->mode;
+}
+
 static const struct attribute_group idxd_group_attribute_group = {
 	.attrs = idxd_group_attributes,
+	.is_visible = idxd_group_attr_visible,
 };
 
 static const struct attribute_group *idxd_group_attribute_groups[] = {