Re: [PATCH v7 06/16] firmware: arm_scmi: Add configurable polling mode for transports

Sudeep Holla
2021-12-13T11:26:03Z

On Mon, Nov 29, 2021 at 07:11:46PM +0000, Cristian Marussi wrote:
> 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@arm.com>
> ---
> v5 --> v6
> - removed check on replies received by IRQs when xfer was requested
> as poll_completion (not all transport can suppress IRQs on an xfer basis)
> 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 | 17 +++++++++++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> index 6438b5248c24..99b74f4d39b6 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;

Do we really need a separate flag for polling_enabled ?
no_completion_irq means you need to enable polling and force_polling too.
Just trying to see if we can get rid of unnecessary flags.

--
Regards,
Sudeep