Commit a690b7e6 authored by Cristian Marussi's avatar Cristian Marussi Committed by Sudeep Holla
Browse files

firmware: arm_scmi: Add configurable polling mode for transports 

SCMI communications along TX channels can optionally be provided of a
completion interrupt; when such interrupt is not available, command
transactions should rely on polling, where the SCMI core takes care to
repeatedly evaluate the transport-specific .poll_done() function, if
available, to determine if and when a request was fully completed or
timed out.

Such mechanism is already present and working on a single transfer base:
SCMI protocols can indeed enable hdr.poll_completion on specific commands
ahead of each transfer and cause that transaction to be handled with
polling.

Introduce a couple of flags to be able to enforce such polling behaviour
globally at will:

 - scmi_desc.force_polling: to statically switch the whole transport to
   polling mode.

 - scmi_chan_info.no_completion_irq: to switch a single channel dynamically
   to polling mode if, at runtime, is determined that no completion
   interrupt was available for such channel.

Link: https://lore.kernel.org/r/20211220195646.44498-2-cristian.marussi@arm.com


Signed-off-by: default avatarCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: default avatarSudeep Holla <sudeep.holla@arm.com>
parent f872af09

drivers/firmware/arm_scmi/common.h

+8 −0
Original line number Diff line number Diff line
@@ -339,11 +339,16 @@ void scmi_protocol_release(const struct scmi_handle *handle, u8 protocol_id); 
 * @dev: Reference to device in the SCMI hierarchy corresponding to this

 *	 channel

 * @handle: Pointer to SCMI entity handle

 * @no_completion_irq: Flag to indicate that this channel has no completion

 *		       interrupt mechanism for synchronous commands.

 *		       This can be dynamically set by transports at run-time

 *		       inside their provided .chan_setup().

 * @transport_info: Transport layer related information

 */

struct scmi_chan_info {

	struct device *dev;

	struct scmi_handle *handle;

	bool no_completion_irq;

	void *transport_info;

};
@@ -402,6 +407,8 @@ struct scmi_device *scmi_child_dev_find(struct device *parent, 
 *	be pending simultaneously in the system. May be overridden by the

 *	get_max_msg op.

 * @max_msg_size: Maximum size of data per message that can be handled.

 * @force_polling: Flag to force this whole transport to use SCMI core polling

 *		   mechanism instead of completion interrupts even if available.

 */

struct scmi_desc {

	int (*transport_init)(void);
@@ -410,6 +417,7 @@ struct scmi_desc { 
	int max_rx_timeout_ms;

	int max_msg;

	int max_msg_size;

	const bool force_polling;

};



#ifdef CONFIG_ARM_SCMI_TRANSPORT_MAILBOX

drivers/firmware/arm_scmi/driver.c

+33 −0
Original line number Diff line number Diff line
@@ -609,6 +609,24 @@ static inline void scmi_clear_channel(struct scmi_info *info, 
		info->desc->ops->clear_channel(cinfo);

}



static inline bool is_polling_required(struct scmi_chan_info *cinfo,

				       struct scmi_info *info)

{

	return cinfo->no_completion_irq || info->desc->force_polling;

}



static inline bool is_transport_polling_capable(struct scmi_info *info)

{

	return info->desc->ops->poll_done;

}



static inline bool is_polling_enabled(struct scmi_chan_info *cinfo,

				      struct scmi_info *info)

{

	return is_polling_required(cinfo, info) &&

		is_transport_polling_capable(info);

}



static void scmi_handle_notification(struct scmi_chan_info *cinfo,

				     u32 msg_hdr, void *priv)

{
@@ -817,6 +835,7 @@ static int do_xfer(const struct scmi_protocol_handle *ph, 
	struct device *dev = info->dev;

	struct scmi_chan_info *cinfo;



	/* Check for polling request on custom command xfers at first */

	if (xfer->hdr.poll_completion && !info->desc->ops->poll_done) {

		dev_warn_once(dev,

			      "Polling mode is not supported by transport.\n");
@@ -827,6 +846,10 @@ static int do_xfer(const struct scmi_protocol_handle *ph, 
	if (unlikely(!cinfo))

		return -EINVAL;



	/* True ONLY if also supported by transport. */

	if (is_polling_enabled(cinfo, info))

		xfer->hdr.poll_completion = true;



	/*

	 * Initialise protocol id now from protocol handle to avoid it being

	 * overridden by mistake (or malice) by the protocol code mangling with
@@ -1527,6 +1550,16 @@ static int scmi_chan_setup(struct scmi_info *info, struct device *dev, 
	if (ret)

		return ret;



	if (tx && is_polling_required(cinfo, info)) {

		if (is_transport_polling_capable(info))

			dev_info(dev,

				 "Enabled polling mode TX channel - prot_id:%d\n",

				 prot_id);

		else

			dev_warn(dev,

				 "Polling mode NOT supported by transport.\n");

	}



idr_alloc:

	ret = idr_alloc(idr, cinfo, prot_id, prot_id + 1, GFP_KERNEL);

	if (ret != prot_id) {