dmaengine: idxd: add support for configurable max wq batch size

Add sysfs attribute max_batch_size to wq in order to allow the max batch
size configured on a per wq basis. Add support code to configure
the valid user input on wq enable. This is a performance tuning
parameter.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/159865273617.29141.4383066301730821749.stgit@djiang5-desk3.ch.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

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

@@ -177,6 +177,13 @@ Contact:	dmaengine@vger.kernel.org
 Description:	The max transfer sized for this workqueue. Cannot exceed device
 		max transfer size. Configurable parameter.
 
+What:		/sys/bus/dsa/devices/wq<m>.<n>/max_batch_size
+Date:		Aug 28, 2020
+KernelVersion:	5.10.0
+Contact:	dmaengine@vger.kernel.org
+Description:	The max batch size for this workqueue. Cannot exceed device
+		max batch size. Configurable parameter.
+
 What:           /sys/bus/dsa/devices/engine<m>.<n>/group_id
 Date:           Oct 25, 2019
 KernelVersion:  5.6.0

drivers/dma/idxd/device.c

@@ -530,7 +530,7 @@ static int idxd_wq_config_write(struct idxd_wq *wq)
 
 	/* bytes 12-15 */
 	wq->wqcfg.max_xfer_shift = ilog2(wq->max_xfer_bytes);
-	wq->wqcfg.max_batch_shift = idxd->hw.gen_cap.max_batch_shift;
+	wq->wqcfg.max_batch_shift = ilog2(wq->max_batch_size);
 
 	dev_dbg(dev, "WQ %d CFGs\n", wq->id);
 	for (i = 0; i < 8; i++) {

drivers/dma/idxd/idxd.h

@@ -115,6 +115,7 @@ struct idxd_wq {
 	struct dma_chan dma_chan;
 	char name[WQ_NAME_SIZE + 1];
 	u64 max_xfer_bytes;
+	u32 max_batch_size;
 };
 
 struct idxd_engine {

drivers/dma/idxd/init.c

@@ -177,6 +177,7 @@ static int idxd_setup_internals(struct idxd_device *idxd)
 		mutex_init(&wq->wq_lock);
 		wq->idxd_cdev.minor = -1;
 		wq->max_xfer_bytes = idxd->max_xfer_bytes;
+		wq->max_batch_size = idxd->max_batch_size;
 	}
 
 	for (i = 0; i < idxd->max_engines; i++) {

drivers/dma/idxd/sysfs.c

@@ -1064,6 +1064,21 @@ static ssize_t wq_cdev_minor_show(struct device *dev,
 static struct device_attribute dev_attr_wq_cdev_minor =
 		__ATTR(cdev_minor, 0444, wq_cdev_minor_show, NULL);
 
+static int __get_sysfs_u64(const char *buf, u64 *val)
+{
+	int rc;
+
+	rc = kstrtou64(buf, 0, val);
+	if (rc < 0)
+		return -EINVAL;
+
+	if (*val == 0)
+		return -EINVAL;
+
+	*val = roundup_pow_of_two(*val);
+	return 0;
+}
+
 static ssize_t wq_max_transfer_size_show(struct device *dev, struct device_attribute *attr,
 					 char *buf)
 {
@@ -1083,14 +1098,10 @@ static ssize_t wq_max_transfer_size_store(struct device *dev, struct device_attr
 	if (wq->state != IDXD_WQ_DISABLED)
 		return -EPERM;
 
-	rc = kstrtou64(buf, 0, &xfer_size);
+	rc = __get_sysfs_u64(buf, &xfer_size);
 	if (rc < 0)
-		return -EINVAL;
-
-	if (xfer_size == 0)
-		return -EINVAL;
+		return rc;
 
-	xfer_size = roundup_pow_of_two(xfer_size);
 	if (xfer_size > idxd->max_xfer_bytes)
 		return -EINVAL;
 
@@ -1103,6 +1114,39 @@ static struct device_attribute dev_attr_wq_max_transfer_size =
 		__ATTR(max_transfer_size, 0644,
 		       wq_max_transfer_size_show, wq_max_transfer_size_store);
 
+static ssize_t wq_max_batch_size_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct idxd_wq *wq = container_of(dev, struct idxd_wq, conf_dev);
+
+	return sprintf(buf, "%u\n", wq->max_batch_size);
+}
+
+static ssize_t wq_max_batch_size_store(struct device *dev, struct device_attribute *attr,
+				       const char *buf, size_t count)
+{
+	struct idxd_wq *wq = container_of(dev, struct idxd_wq, conf_dev);
+	struct idxd_device *idxd = wq->idxd;
+	u64 batch_size;
+	int rc;
+
+	if (wq->state != IDXD_WQ_DISABLED)
+		return -EPERM;
+
+	rc = __get_sysfs_u64(buf, &batch_size);
+	if (rc < 0)
+		return rc;
+
+	if (batch_size > idxd->max_batch_size)
+		return -EINVAL;
+
+	wq->max_batch_size = (u32)batch_size;
+
+	return count;
+}
+
+static struct device_attribute dev_attr_wq_max_batch_size =
+		__ATTR(max_batch_size, 0644, wq_max_batch_size_show, wq_max_batch_size_store);
+
 static struct attribute *idxd_wq_attributes[] = {
 	&dev_attr_wq_clients.attr,
 	&dev_attr_wq_state.attr,
@@ -1114,6 +1158,7 @@ static struct attribute *idxd_wq_attributes[] = {
 	&dev_attr_wq_name.attr,
 	&dev_attr_wq_cdev_minor.attr,
 	&dev_attr_wq_max_transfer_size.attr,
+	&dev_attr_wq_max_batch_size.attr,
 	NULL,
 };