[PATCH net-next 1/3] bus: mhi: core: Add helper API to return number of free TREs

From: Hemant Kumar <redacted>

Introduce mhi_get_free_desc_count() API to return number
of TREs available to queue buffer. MHI clients can use this
API to know before hand if ring is full without calling queue
API.

Signed-off-by: Hemant Kumar <redacted>
Reviewed-by: Jeffrey Hugo <redacted>
Reviewed-by: Manivannan Sadhasivam <redacted>
---
 drivers/bus/mhi/core/main.c | 12 ++++++++++++
 include/linux/mhi.h         |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 3db1108..4e31f4f 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c

@@ -309,6 +309,18 @@ int mhi_destroy_device(struct device *dev, void *data)
 	return 0;
 }
 
+int mhi_get_free_desc_count(struct mhi_device *mhi_dev,
+				enum dma_data_direction dir)
+{
+	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
+	struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ?
+		mhi_dev->ul_chan : mhi_dev->dl_chan;
+	struct mhi_ring *tre_ring = &mhi_chan->tre_ring;
+
+	return get_nr_avail_ring_elements(mhi_cntrl, tre_ring);
+}
+EXPORT_SYMBOL_GPL(mhi_get_free_desc_count);
+
 void mhi_notify(struct mhi_device *mhi_dev, enum mhi_callback cb_reason)
 {
 	struct mhi_driver *mhi_drv;

diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index cd571ad..62da830 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h

@@ -614,6 +614,15 @@ void mhi_set_mhi_state(struct mhi_controller *mhi_cntrl,
 void mhi_notify(struct mhi_device *mhi_dev, enum mhi_callback cb_reason);
 
 /**
+ * mhi_get_free_desc_count - Get transfer ring length
+ * Get # of TD available to queue buffers
+ * @mhi_dev: Device associated with the channels
+ * @dir: Direction of the channel
+ */
+int mhi_get_free_desc_count(struct mhi_device *mhi_dev,
+				enum dma_data_direction dir);
+
+/**
  * mhi_prepare_for_power_up - Do pre-initialization before power up.
  *                            This is optional, call this before power up if
  *                            the controller does not want bus framework to

-- 
2.7.4

The RX queue size can be determined at runtime by retrieving the
number of available transfer descriptors.

Signed-off-by: Loic Poulain <redacted>
---
 drivers/net/mhi_net.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/mhi_net.c b/drivers/net/mhi_net.c
index b7f7f2e..3da820b 100644
--- a/drivers/net/mhi_net.c
+++ b/drivers/net/mhi_net.c

@@ -257,9 +257,6 @@ static int mhi_net_probe(struct mhi_device *mhi_dev,
 	mhi_netdev->mdev = mhi_dev;
 	SET_NETDEV_DEV(ndev, &mhi_dev->dev);
 
-	/* All MHI net channels have 128 ring elements (at least for now) */
-	mhi_netdev->rx_queue_sz = 128;
-
 	INIT_DELAYED_WORK(&mhi_netdev->rx_refill, mhi_net_rx_refill_work);
 	u64_stats_init(&mhi_netdev->stats.rx_syncp);
 	u64_stats_init(&mhi_netdev->stats.tx_syncp);

@@ -269,6 +266,9 @@ static int mhi_net_probe(struct mhi_device *mhi_dev,
 	if (err)
 		goto out_err;
 
+	/* Number of transfer descriptors determines size of the queue */
+	mhi_netdev->rx_queue_sz = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);
+
 	err = register_netdev(ndev);
 	if (err)
 		goto out_err;

-- 
2.7.4

Use the new mhi_get_free_desc_count helper to track queue usage
instead of relying on the locally maintained rx_queued count.

Signed-off-by: Loic Poulain <redacted>
---
 drivers/net/mhi_net.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/net/mhi_net.c b/drivers/net/mhi_net.c
index 3da820b..f83562d 100644
--- a/drivers/net/mhi_net.c
+++ b/drivers/net/mhi_net.c

@@ -25,7 +25,6 @@ struct mhi_net_stats {
 	u64_stats_t tx_bytes;
 	u64_stats_t tx_errors;
 	u64_stats_t tx_dropped;
-	atomic_t rx_queued;
 	struct u64_stats_sync tx_syncp;
 	struct u64_stats_sync rx_syncp;
 };

@@ -138,9 +137,9 @@ static void mhi_net_dl_callback(struct mhi_device *mhi_dev,
 {
 	struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
 	struct sk_buff *skb = mhi_res->buf_addr;
-	int remaining;
+	int free_desc_count;
 
-	remaining = atomic_dec_return(&mhi_netdev->stats.rx_queued);
+	free_desc_count = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);
 
 	if (unlikely(mhi_res->transaction_status)) {
 		dev_kfree_skb_any(skb);

@@ -164,7 +163,7 @@ static void mhi_net_dl_callback(struct mhi_device *mhi_dev,
 	}
 
 	/* Refill if RX buffers queue becomes low */
-	if (remaining <= mhi_netdev->rx_queue_sz / 2)
+	if (free_desc_count >= mhi_netdev->rx_queue_sz / 2)
 		schedule_delayed_work(&mhi_netdev->rx_refill, 0);
 }
 

@@ -211,7 +210,7 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
 	struct sk_buff *skb;
 	int err;
 
-	while (atomic_read(&mhi_netdev->stats.rx_queued) < mhi_netdev->rx_queue_sz) {
+	while (!mhi_queue_is_full(mdev, DMA_FROM_DEVICE)) {
 		skb = netdev_alloc_skb(ndev, size);
 		if (unlikely(!skb))
 			break;

@@ -224,8 +223,6 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
 			break;
 		}
 
-		atomic_inc(&mhi_netdev->stats.rx_queued);
-
 		/* Do not hog the CPU if rx buffers are consumed faster than
 		 * queued (unlikely).
 		 */

@@ -233,7 +230,7 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
 	}
 
 	/* If we're still starved of rx buffers, reschedule later */
-	if (unlikely(!atomic_read(&mhi_netdev->stats.rx_queued)))
+	if (mhi_get_free_desc_count(mdev, DMA_FROM_DEVICE) == mhi_netdev->rx_queue_sz)
 		schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
 }
 

-- 
2.7.4

On Mon, 11 Jan 2021 19:07:40 +0100 Loic Poulain wrote:

From: Hemant Kumar <redacted>

Introduce mhi_get_free_desc_count() API to return number
of TREs available to queue buffer. MHI clients can use this
API to know before hand if ring is full without calling queue
API.

Signed-off-by: Hemant Kumar <redacted>
Reviewed-by: Jeffrey Hugo <redacted>
Reviewed-by: Manivannan Sadhasivam <redacted>

Can we apply these to net-next or does it need to be on a stable branch
that will also get pulled into mhi-next?

On Wed, Jan 13, 2021 at 07:33:01PM -0800, Jakub Kicinski wrote:

On Mon, 11 Jan 2021 19:07:40 +0100 Loic Poulain wrote:

quoted

From: Hemant Kumar <redacted>

Introduce mhi_get_free_desc_count() API to return number
of TREs available to queue buffer. MHI clients can use this
API to know before hand if ring is full without calling queue
API.

Signed-off-by: Hemant Kumar <redacted>
Reviewed-by: Jeffrey Hugo <redacted>
Reviewed-by: Manivannan Sadhasivam <redacted>

Can we apply these to net-next or does it need to be on a stable branch
that will also get pulled into mhi-next?

We should use the immutable branch for this so that I can pull into
mhi-next.

Thanks,
Mani

On Thu, 14 Jan 2021 09:27:49 +0530 Manivannan Sadhasivam wrote:

On Wed, Jan 13, 2021 at 07:33:01PM -0800, Jakub Kicinski wrote:

quoted

On Mon, 11 Jan 2021 19:07:40 +0100 Loic Poulain wrote:  

quoted

From: Hemant Kumar <redacted>

Introduce mhi_get_free_desc_count() API to return number
of TREs available to queue buffer. MHI clients can use this
API to know before hand if ring is full without calling queue
API.

Signed-off-by: Hemant Kumar <redacted>
Reviewed-by: Jeffrey Hugo <redacted>
Reviewed-by: Manivannan Sadhasivam <redacted>  

Can we apply these to net-next or does it need to be on a stable branch
that will also get pulled into mhi-next?  

We should use the immutable branch for this so that I can pull into
mhi-next.

Thanks for a quire reply!

Loic, FWIW git merge-base is your friend.

On Wed, Jan 13, 2021 at 08:02:46PM -0800, Jakub Kicinski wrote:

On Thu, 14 Jan 2021 09:27:49 +0530 Manivannan Sadhasivam wrote:

quoted

On Wed, Jan 13, 2021 at 07:33:01PM -0800, Jakub Kicinski wrote:

quoted

On Mon, 11 Jan 2021 19:07:40 +0100 Loic Poulain wrote:  

quoted

From: Hemant Kumar <redacted>

Introduce mhi_get_free_desc_count() API to return number
of TREs available to queue buffer. MHI clients can use this
API to know before hand if ring is full without calling queue
API.

Signed-off-by: Hemant Kumar <redacted>
Reviewed-by: Jeffrey Hugo <redacted>
Reviewed-by: Manivannan Sadhasivam <redacted>  

Can we apply these to net-next or does it need to be on a stable branch
that will also get pulled into mhi-next?  

We should use the immutable branch for this so that I can pull into
mhi-next.

Please find the immutable branch:
https://git.kernel.org/pub/scm/linux/kernel/git/mani/mhi.git/log/?h=mhi-net-immutable

I've now merged this into mhi-next!

Thanks,
Mani

Thanks for a quire reply!

Loic, FWIW git merge-base is your friend.

On Wed, 27 Jan 2021 16:53:17 +0530 Manivannan Sadhasivam wrote:

On Wed, Jan 13, 2021 at 08:02:46PM -0800, Jakub Kicinski wrote:

quoted

On Thu, 14 Jan 2021 09:27:49 +0530 Manivannan Sadhasivam wrote:  

quoted

On Wed, Jan 13, 2021 at 07:33:01PM -0800, Jakub Kicinski wrote:  

quoted

On Mon, 11 Jan 2021 19:07:40 +0100 Loic Poulain wrote:    

quoted

From: Hemant Kumar <redacted>

Introduce mhi_get_free_desc_count() API to return number
of TREs available to queue buffer. MHI clients can use this
API to know before hand if ring is full without calling queue
API.

Signed-off-by: Hemant Kumar <redacted>
Reviewed-by: Jeffrey Hugo <redacted>
Reviewed-by: Manivannan Sadhasivam <redacted>    

Can we apply these to net-next or does it need to be on a stable branch
that will also get pulled into mhi-next?    

We should use the immutable branch for this so that I can pull into
mhi-next.  

Please find the immutable branch:
https://git.kernel.org/pub/scm/linux/kernel/git/mani/mhi.git/log/?h=mhi-net-immutable

I've now merged this into mhi-next!

Loic, please prepare a proper pull request based on that with the other
patches included.