linux-kernel - Re: [PATCH v7 08/16] firmware: arm_scmi: Add sync_cmds_atomic

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Message-ID: <20211214105240.GF6207@e120937-lin>
Date:   Tue, 14 Dec 2021 10:52:40 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com,
        f.fainelli@...il.com, etienne.carriere@...aro.org,
        vincent.guittot@...aro.org, souvik.chakravarty@....com
Subject: Re: [PATCH v7 08/16] firmware: arm_scmi: Add
 sync_cmds_atomic_replies transport flag

On Mon, Dec 13, 2021 at 11:54:37AM +0000, Sudeep Holla wrote:
> On Mon, Nov 29, 2021 at 07:11:48PM +0000, Cristian Marussi wrote:
> > Add a flag to let the transport signal to the core if its handling of sync
> > command implies that, after .send_message has returned successfully, the
> > requested command can be assumed to be fully and completely executed on
> > SCMI platform side so that any possible response value is already
> > immediately available to be retrieved by a .fetch_response: in other words
> > the polling phase can be skipped in such a case and the response values
> > accessed straight away.
> > 
> > Note that all of the above applies only when polling mode of operation was
> > selected by the core: if instead a completion IRQ was found to be available
> > the normal response processing path based on completions will still be
> > followed.
> > 
> > Signed-off-by: Cristian Marussi <cristian.marussi@....com>
> > ---
> > v5 --> v6
> > - added polling_capable helper flag
> > v4 --> v5
> > - removed RFC tag
> > - consider sync_cmds_atomic_replies flag when deciding if polling is to be
> >   supported and .poll_done() is not provided.
> > - reviewed commit message
> > ---
> >  drivers/firmware/arm_scmi/common.h |  8 ++++++
> >  drivers/firmware/arm_scmi/driver.c | 43 +++++++++++++++++++++++-------
> >  2 files changed, 41 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> > index 99b74f4d39b6..bf25f0e89c78 100644
> > --- a/drivers/firmware/arm_scmi/common.h
> > +++ b/drivers/firmware/arm_scmi/common.h
> > @@ -412,6 +412,13 @@ struct scmi_device *scmi_child_dev_find(struct device *parent,
> >   * @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.
> > + * @sync_cmds_atomic_replies: Flag to indicate that the transport assures
> > + *			      synchronous-command messages are atomically
> > + *			      completed on .send_message: no need to poll
> > + *			      actively waiting for a response.
> 
> Not sure if atomic is right term to use. It is atomic w.r.t OSPM though.
> Can we just say sync_cmd_complete_on_ret or something similar.
> 
Yes, I really never liked the naming so I'll happily take you suggestion :D

Thanks,
Cristian