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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: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
This commit is contained in:
Cristian Marussi 2021-12-20 19:56:36 +00:00 committed by Sudeep Holla
parent f872af0909
commit a690b7e6e7
2 changed files with 41 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/firmware/arm_scmi/common.h
View File

@ -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

33
drivers/firmware/arm_scmi/driver.c
View File

@ -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) {