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Date: Thu, 23 Sep 2021 15:57:51 +0100 From: Cristian Marussi <cristian.marussi@....com> To: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org Cc: sudeep.holla@....com, james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com, f.fainelli@...il.com, etienne.carriere@...aro.org, vincent.guittot@...aro.org, souvik.chakravarty@....com, peter.hilber@...nsynergy.com, igor.skalkin@...nsynergy.com, cristian.marussi@....com Subject: [PATCH v5 02/13] 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. Signed-off-by: Cristian Marussi <cristian.marussi@....com> --- v4 --> v5 - make force_polling const - introduce polling_enabled flag to simplify checks on do_xfer v3 --> v4: - renamed .needs_polling flag to .no_completion_irq - refactored error path when polling needed but not supported --- drivers/firmware/arm_scmi/common.h | 11 +++++++++++ drivers/firmware/arm_scmi/driver.c | 26 ++++++++++++++++++++++++++ 2 files changed, 37 insertions(+) diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h index dea1bfbe1052..fba4c3fd59c8 100644 --- a/drivers/firmware/arm_scmi/common.h +++ b/drivers/firmware/arm_scmi/common.h @@ -339,11 +339,19 @@ 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(). + * @polling_enabled: Flag used to annotate if polling mode is currently enabled + * on this channel. * @transport_info: Transport layer related information */ struct scmi_chan_info { struct device *dev; struct scmi_handle *handle; + bool no_completion_irq; + bool polling_enabled; void *transport_info; }; @@ -402,6 +410,8 @@ 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 +420,7 @@ 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 diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c index 01c79a8fa77f..2e70431ffdd7 100644 --- a/drivers/firmware/arm_scmi/driver.c +++ b/drivers/firmware/arm_scmi/driver.c @@ -656,6 +656,15 @@ static void scmi_handle_response(struct scmi_chan_info *cinfo, return; } + /* Discard unexpected messages when polling is active. */ + if (xfer->hdr.type != MSG_TYPE_DELAYED_RESP && + xfer->hdr.poll_completion) { + WARN_ON_ONCE(1); + dev_dbg(cinfo->dev, + "Completion IRQ received but using polling. Ignore.\n"); + return; + } + /* rx.len could be shrunk in the sync do_xfer, so reset to maxsz */ if (xfer->hdr.type == MSG_TYPE_DELAYED_RESP) xfer->rx.len = info->desc->max_msg_size; @@ -760,6 +769,7 @@ 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"); @@ -770,6 +780,10 @@ static int do_xfer(const struct scmi_protocol_handle *ph, if (unlikely(!cinfo)) return -EINVAL; + /* Initialized to true ONLY if also supported by transport. */ + if (cinfo->polling_enabled) + 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 @@ -1499,6 +1513,18 @@ static int scmi_chan_setup(struct scmi_info *info, struct device *dev, if (ret) return ret; + if (tx && (cinfo->no_completion_irq || info->desc->force_polling)) { + if (info->desc->ops->poll_done) { + dev_info(dev, + "Enabled polling mode TX channel - prot_id:%d\n", + prot_id); + cinfo->polling_enabled = true; + } 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) { -- 2.17.1
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