diff mbox series

[v2,1/3] bus: mhi: core: Add helper API to return number of free TREs

Message ID 1607598951-2340-1-git-send-email-loic.poulain@linaro.org
State Superseded
Headers show
Series [v2,1/3] bus: mhi: core: Add helper API to return number of free TREs | expand

Commit Message

Loic Poulain Dec. 10, 2020, 11:15 a.m. UTC 
From: Hemant Kumar <hemantk@codeaurora.org>


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 <hemantk@codeaurora.org>

Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

---
 v2: no change

 drivers/bus/mhi/core/main.c | 12 ++++++++++++
 include/linux/mhi.h         |  9 +++++++++
 2 files changed, 21 insertions(+)

-- 
2.7.4

Comments

Manivannan Sadhasivam Dec. 11, 2020, 5:38 a.m. UTC | #1 
On Thu, Dec 10, 2020 at 12:15:50PM +0100, Loic Poulain wrote:
> The RX queue size can be determined at runtime by retrieving the
> number of available transfer descriptors.
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> ---
>  v2: Fixed commit message typo
> 
>  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 8e72d94..0333e07 100644
> --- a/drivers/net/mhi_net.c
> +++ b/drivers/net/mhi_net.c
> @@ -256,9 +256,6 @@ 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);
> @@ -268,6 +265,9 @@ 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);
> +

This value is not static right? You might need to fetch the count in
mhi_net_rx_refill_work().

Thanks,
Mani

>  	err = register_netdev(ndev);
>  	if (err)
>  		goto out_err;
> -- 
> 2.7.4
>
Manivannan Sadhasivam Dec. 11, 2020, 10:15 a.m. UTC | #2 
On Fri, Dec 11, 2020 at 10:40:13AM +0100, Loic Poulain wrote:
> Hi Mani,

> 

> On Fri, 11 Dec 2020 at 06:38, Manivannan Sadhasivam

> <manivannan.sadhasivam@linaro.org> wrote:

> >

> > On Thu, Dec 10, 2020 at 12:15:50PM +0100, Loic Poulain wrote:

> > > The RX queue size can be determined at runtime by retrieving the

> > > number of available transfer descriptors.

> > >

> > > Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

> > > ---

> > >  v2: Fixed commit message typo

> > >

> > >  drivers/net/mhi_net.c | 6 +++---

> > >  1 file changed, 3 insertions(+), 3 deletions(-)

> [...]

> > > -

> > >       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);

> > > @@ -268,6 +265,9 @@ 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);

> > > +

> >

> > This value is not static right? You might need to fetch the count in

> > mhi_net_rx_refill_work().

> 

> It is, actually here driver is just looking for the total queue size,

> which is the number of descriptors at init time. This total queue size

> is used later to determine the level of MHI queue occupancy rate.

> 


Right but what if the size got increased in runtime (recycled etc...), we won't
be fully utilizing the ring.

Thanks,
Mani

> Regards,

> Loic
Loic Poulain Dec. 11, 2020, 10:40 a.m. UTC | #3 
On Fri, 11 Dec 2020 at 11:15, Manivannan Sadhasivam
<manivannan.sadhasivam@linaro.org> wrote:
>

> On Fri, Dec 11, 2020 at 10:40:13AM +0100, Loic Poulain wrote:

> > Hi Mani,

> >

> > On Fri, 11 Dec 2020 at 06:38, Manivannan Sadhasivam

> > <manivannan.sadhasivam@linaro.org> wrote:

> > >

> > > On Thu, Dec 10, 2020 at 12:15:50PM +0100, Loic Poulain wrote:

> > > > The RX queue size can be determined at runtime by retrieving the

> > > > number of available transfer descriptors.

> > > >

> > > > Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

> > > > ---

> > > >  v2: Fixed commit message typo

> > > >

> > > >  drivers/net/mhi_net.c | 6 +++---

> > > >  1 file changed, 3 insertions(+), 3 deletions(-)

> > [...]

> > > > -

> > > >       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);

> > > > @@ -268,6 +265,9 @@ 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);

> > > > +

> > >

> > > This value is not static right? You might need to fetch the count in

> > > mhi_net_rx_refill_work().

> >

> > It is, actually here driver is just looking for the total queue size,

> > which is the number of descriptors at init time. This total queue size

> > is used later to determine the level of MHI queue occupancy rate.

> >

>

> Right but what if the size got increased in runtime (recycled etc...), we won't

> be fully utilizing the ring.


The queue size can not be more than the initial size, which is the
number of elements in the rings (e.g. 128). At runtime, the driver
calls again mhi_get_free_desc_count() in DL callback to determine the
current number available slots (e.g. 32). If this value is higher than
a certain limit (e.g 128 /2), then we start refilling the MHI RX queue
with fresh buffers to prevent buffer starvation.

Regards,
Loic
diff mbox series

Patch

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 54d9c80..a24ba4f 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -303,6 +303,18 @@  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 09f786e..25c69a0 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -616,6 +616,15 @@  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