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rpmsg: core: Add signal API support
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Some transports like Glink support the state notifications between
clients using flow control signals similar to serial protocol signals.
Local glink client drivers can send and receive flow control status
to glink clients running on remote processors.

Add APIs to support sending and receiving of flow control status by
rpmsg clients.

Signed-off-by: Deepak Kumar Singh <quic_deesin@quicinc.com>
Signed-off-by: Sarannya S <quic_sarannya@quicinc.com>
Acked-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/1688679698-31274-2-git-send-email-quic_sarannya@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
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Deepak Kumar Singh authored and Bjorn Andersson committed Jul 15, 2023
1 parent 06c2afb commit 8ce49c2
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21 changes: 21 additions & 0 deletions drivers/rpmsg/rpmsg_core.c
Original file line number Diff line number Diff line change
Expand Up @@ -330,6 +330,25 @@ int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
}
EXPORT_SYMBOL(rpmsg_trysend_offchannel);

/**
* rpmsg_set_flow_control() - request remote to pause/resume transmission
* @ept: the rpmsg endpoint
* @pause: pause transmission
* @dst: destination address of the endpoint
*
* Return: 0 on success and an appropriate error value on failure.
*/
int rpmsg_set_flow_control(struct rpmsg_endpoint *ept, bool pause, u32 dst)
{
if (WARN_ON(!ept))
return -EINVAL;
if (!ept->ops->set_flow_control)
return -EOPNOTSUPP;

return ept->ops->set_flow_control(ept, pause, dst);
}
EXPORT_SYMBOL_GPL(rpmsg_set_flow_control);

/**
* rpmsg_get_mtu() - get maximum transmission buffer size for sending message.
* @ept: the rpmsg endpoint
Expand Down Expand Up @@ -539,6 +558,8 @@ static int rpmsg_dev_probe(struct device *dev)

rpdev->ept = ept;
rpdev->src = ept->addr;

ept->flow_cb = rpdrv->flowcontrol;
}

err = rpdrv->probe(rpdev);
Expand Down
2 changes: 2 additions & 0 deletions drivers/rpmsg/rpmsg_internal.h
Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ struct rpmsg_device_ops {
* @trysendto: see @rpmsg_trysendto(), optional
* @trysend_offchannel: see @rpmsg_trysend_offchannel(), optional
* @poll: see @rpmsg_poll(), optional
* @set_flow_control: see @rpmsg_set_flow_control(), optional
* @get_mtu: see @rpmsg_get_mtu(), optional
*
* Indirection table for the operations that a rpmsg backend should implement.
Expand All @@ -75,6 +76,7 @@ struct rpmsg_endpoint_ops {
void *data, int len);
__poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
poll_table *wait);
int (*set_flow_control)(struct rpmsg_endpoint *ept, bool pause, u32 dst);
ssize_t (*get_mtu)(struct rpmsg_endpoint *ept);
};

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15 changes: 15 additions & 0 deletions include/linux/rpmsg.h
Original file line number Diff line number Diff line change
Expand Up @@ -64,12 +64,14 @@ struct rpmsg_device {
};

typedef int (*rpmsg_rx_cb_t)(struct rpmsg_device *, void *, int, void *, u32);
typedef int (*rpmsg_flowcontrol_cb_t)(struct rpmsg_device *, void *, bool);

/**
* struct rpmsg_endpoint - binds a local rpmsg address to its user
* @rpdev: rpmsg channel device
* @refcount: when this drops to zero, the ept is deallocated
* @cb: rx callback handler
* @flow_cb: remote flow control callback handler
* @cb_lock: must be taken before accessing/changing @cb
* @addr: local rpmsg address
* @priv: private data for the driver's use
Expand All @@ -92,6 +94,7 @@ struct rpmsg_endpoint {
struct rpmsg_device *rpdev;
struct kref refcount;
rpmsg_rx_cb_t cb;
rpmsg_flowcontrol_cb_t flow_cb;
struct mutex cb_lock;
u32 addr;
void *priv;
Expand All @@ -106,13 +109,15 @@ struct rpmsg_endpoint {
* @probe: invoked when a matching rpmsg channel (i.e. device) is found
* @remove: invoked when the rpmsg channel is removed
* @callback: invoked when an inbound message is received on the channel
* @flowcontrol: invoked when remote side flow control request is received
*/
struct rpmsg_driver {
struct device_driver drv;
const struct rpmsg_device_id *id_table;
int (*probe)(struct rpmsg_device *dev);
void (*remove)(struct rpmsg_device *dev);
int (*callback)(struct rpmsg_device *, void *, int, void *, u32);
int (*flowcontrol)(struct rpmsg_device *, void *, bool);
};

static inline u16 rpmsg16_to_cpu(struct rpmsg_device *rpdev, __rpmsg16 val)
Expand Down Expand Up @@ -192,6 +197,8 @@ __poll_t rpmsg_poll(struct rpmsg_endpoint *ept, struct file *filp,

ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept);

int rpmsg_set_flow_control(struct rpmsg_endpoint *ept, bool pause, u32 dst);

#else

static inline int rpmsg_register_device_override(struct rpmsg_device *rpdev,
Expand Down Expand Up @@ -316,6 +323,14 @@ static inline ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept)
return -ENXIO;
}

static inline int rpmsg_set_flow_control(struct rpmsg_endpoint *ept, bool pause, u32 dst)
{
/* This shouldn't be possible */
WARN_ON(1);

return -ENXIO;
}

#endif /* IS_ENABLED(CONFIG_RPMSG) */

/* use a macro to avoid include chaining to get THIS_MODULE */
Expand Down

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