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Mon, 4 Oct 2021 11:00:36 -0700 (PDT) Date: Mon, 4 Oct 2021 19:00:26 +0100 From: Cristian Marussi To: Jim Quinlan Cc: Florian Fainelli , open list , "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" , Sudeep Holla , Jonathan Cameron , etienne.carriere@linaro.org, Vincent Guittot , Souvik Chakravarty Subject: Re: [PATCH v4 11/12] [RFC] firmware: arm_scmi: Add sync_cmds_atomic_replies transport flag Message-ID: <20211004180011.GA6376@e120937-lin> References: <20210824135941.38656-1-cristian.marussi@arm.com> <20210824135941.38656-12-cristian.marussi@arm.com> <7a2f972d-fdd0-d0f7-cac2-1989980ed872@gmail.com> <20210825184915.GI13160@e120937-lin> <20210923150319.GC6510@e120937-lin> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211004_110042_821062_6DC6A29B X-CRM114-Status: GOOD ( 47.65 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 04, 2021 at 01:50:04PM -0400, Jim Quinlan wrote: > On Thu, Sep 23, 2021 at 11:03 AM Cristian Marussi > wrote: > > > > On Thu, Aug 26, 2021 at 02:29:21PM -0400, Jim Quinlan wrote: > > > On Wed, Aug 25, 2021 at 2:49 PM Cristian Marussi > > > wrote: > > > > > > > > On Wed, Aug 25, 2021 at 01:17:47PM -0400, Jim Quinlan wrote: > > > > > On Wed, Aug 25, 2021 at 12:38 PM Florian Fainelli wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Florian and Jim, > > > > > > > > > > On 8/24/2021 3:59 PM, Cristian Marussi wrote: > > > > > > > A flag is added to let the transport signal the core that its handling of > > > > > > > synchronous command messages 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_reponse: > > > > > > > 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. > > > > > > > > > > > > This might actually have to be settable on a per-message basis ideally > > > > > > since we may be transporting short lived SCMI messages for which the > > > > > > completion can be done at SMC time, and long lived SCMI messages (e.g.: > > > > > > involving a voltage change) for which we would prefer a completion > > > > > > interrupt. Jim, what do you think? > > > > > Even if the SCMI main driver could be configured this way in an > > > > > elegant manner, I'm not sure that there is a clean way of specifying > > > > > this attribute on a per-message basis. Certainly we could do this > > > > > with our own protocols, but many of our "long lived" messages are the > > > > > Perf protocol's set_level command. At any rate, let me give it some > > > > > thought. > > > > > > > > > > > > > The new flag .sync_cmds_atomic_replies applies only when polling mode > > > > has been selected for a specific cmd transaction, which means when no > > > > completion IRQ was found available OR if xfer.poll_completion was > > > > excplicitly set for a specific command. > > > > > > > > At the moment in this series (unknown bugs apart :D), if you have a > > > > channel configured with a completion IRQ and the .sync_cmds_atomic_replies > > > > set for the transport, this latter flag would be generally ignored and a > > > > wait_for_completion() will be normally used upon reception of the > > > > completionIRQ, UNLESS you specify that one specific command has to be > > > > polled using the per message xfer.poll_completion flag: so you should be > > > > already able to selectively use a polling which immediately returns after > > > > the smc by setting xfer.poll_completion for that specific short lived > > > > message (since sync_cmds_atomic_replies is set and applies to pollmode). > > > > On the other side any other LONG lived message will be naturally handled > > > > via completionIRQ + wait_for_completion. (at least that was the aim..) > > > > > > > > !!! NOTE that you'll have also to drop > > > > > > > > [PATCH v4 10/12] [RFC] firmware: arm_scmi: Make smc transport atomic > > > > > > > > from this series for the wait_completion to happen as you wish. > > > > > > Hi Cristian, > > > > > > > Hi Jim, > > > > > I've tested all commits on our SMC-based system. I also tested all commits > > > minus "10/12 [RFC] firmware: arm_scmi: Make smc transport atomic". > > > This was a basic stress test, not a comprehensive one. So > > > > > > Tested-by: Jim Quinlan > > > > > > Of course I have a strong preference for omitting "10/12 [RFC]" :-). > > > FWIW, if you are not planning on dropping this commit, perhaps there > > > could be a transport > > > node in the DT, and that could contain the a bool property > > > "smc-atomic-capable"? > > > > > > > I just posted V5 on this SCMI atomic transport series, where the atomic > > mode behaviour of a transport can be selected by a Kconfig which is defined > > as default N: so this new series should behave out-of-the-box like with the > > previous one when you had dropped as a whole the SMC atomic patch. > > > > Any feedback welcome. > > Hi Christian, > Hi Jim, > This is very much appreciated, thanks! No feedback except > > Tested-by: Jim Quinlan > Glad to hear that. I'll see if I can gather more feedback from other partners that were interested on using the atomic path (which was supposed to be the main feature of this series at the end :D...) Thanks for your testing. Cristian > Thanks again, > Jim > > > > > > Thanks, > > Cristian > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel