[PATCH 1/2] dmaengine: idxd: add support for configurable max wq xfer size

[Dave Jiang <dave.jiang@xxxxxxxxx>]

Add sysfs attribute max_xfer_size to wq in order to allow the max xfer
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@xxxxxxxxx>
---
 drivers/dma/idxd/device.c |    2 +-
 drivers/dma/idxd/idxd.h   |    1 +
 drivers/dma/idxd/init.c   |    1 +
 drivers/dma/idxd/sysfs.c  |   40 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 14b45853aa5f..b8dbb7001933 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -529,7 +529,7 @@ static int idxd_wq_config_write(struct idxd_wq *wq)
 	wq->wqcfg.priority = wq->priority;
 
 	/* bytes 12-15 */
-	wq->wqcfg.max_xfer_shift = idxd->hw.gen_cap.max_xfer_shift;
+	wq->wqcfg.max_xfer_shift = ilog2(wq->max_xfer_bytes);
 	wq->wqcfg.max_batch_shift = idxd->hw.gen_cap.max_batch_shift;
 
 	dev_dbg(dev, "WQ %d CFGs\n", wq->id);
diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
index e62b4799d189..81db2a472822 100644
--- a/drivers/dma/idxd/idxd.h
+++ b/drivers/dma/idxd/idxd.h
@@ -114,6 +114,7 @@ struct idxd_wq {
 	struct sbitmap_queue sbq;
 	struct dma_chan dma_chan;
 	char name[WQ_NAME_SIZE + 1];
+	u64 max_xfer_bytes;
 };
 
 struct idxd_engine {
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index c7c61974f20f..e5ed5750a6d0 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -176,6 +176,7 @@ static int idxd_setup_internals(struct idxd_device *idxd)
 		wq->idxd = idxd;
 		mutex_init(&wq->wq_lock);
 		wq->idxd_cdev.minor = -1;
+		wq->max_xfer_bytes = idxd->max_xfer_bytes;
 	}
 
 	for (i = 0; i < idxd->max_engines; i++) {
diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
index dcba60953217..26b3ace66782 100644
--- a/drivers/dma/idxd/sysfs.c
+++ b/drivers/dma/idxd/sysfs.c
@@ -1064,6 +1064,45 @@ 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 ssize_t wq_max_transfer_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, "%llu\n", wq->max_xfer_bytes);
+}
+
+static ssize_t wq_max_transfer_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 xfer_size;
+	int rc;
+
+	if (wq->state != IDXD_WQ_DISABLED)
+		return -EPERM;
+
+	rc = kstrtou64(buf, 10, &xfer_size);
+	if (rc < 0)
+		return -EINVAL;
+
+	if (xfer_size == 0)
+		return -EINVAL;
+
+	xfer_size = roundup_pow_of_two(xfer_size);
+	if (xfer_size > idxd->max_xfer_bytes)
+		return -EINVAL;
+
+	wq->max_xfer_bytes = xfer_size;
+
+	return count;
+}
+
+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 struct attribute *idxd_wq_attributes[] = {
 	&dev_attr_wq_clients.attr,
 	&dev_attr_wq_state.attr,
@@ -1074,6 +1113,7 @@ static struct attribute *idxd_wq_attributes[] = {
 	&dev_attr_wq_type.attr,
 	&dev_attr_wq_name.attr,
 	&dev_attr_wq_cdev_minor.attr,
+	&dev_attr_wq_max_transfer_size.attr,
 	NULL,
 };