> From: Sudeep Holla <sudeep.ho...@arm.com> > Date: Tue, Jan 5, 2021 at 12:35 PM > Subject: Re: [PATCH v4 2/2] firmware: arm_scmi: Augment SMC/HVC to allow > optional interrupt > To: Florian Fainelli <f.faine...@gmail.com> > Cc: Jim Quinlan <jim2101...@gmail.com>, Sudeep Holla <sudeep.ho...@arm.com>, > <bcm-kernel-feedback-l...@broadcom.com>, <james.quin...@broadcom.com>, open > list:SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE Mes... > <linux-arm-ker...@lists.infradead.org>, open list > <linux-kernel@vger.kernel.org> > > > On Tue, Dec 22, 2020 at 07:37:22PM -0800, Florian Fainelli wrote: > > > > > > On 12/22/2020 6:56 AM, Jim Quinlan wrote: > > > The SMC/HVC SCMI transport is modified to allow the completion of an SCMI > > > message to be indicated by an interrupt rather than the return of the smc > > > call. This accommodates the existing behavior of the BrcmSTB SCMI > > > "platform" whose SW is already out in the field and cannot be changed. > > > > > > Signed-off-by: Jim Quinlan <jim2101...@gmail.com> > > > > This looks good to me, just one question below: > > > > [snip] > > > > > @@ -111,6 +145,8 @@ static int smc_send_message(struct scmi_chan_info > > > *cinfo, > > > shmem_tx_prepare(scmi_info->shmem, xfer); > > > > > > arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res); > > > + if (scmi_info->irq) > > > + wait_for_completion(&scmi_info->tx_complete); > > > > Do we need this to have a preceding call to reinit_completion()? It does > > not look like this is going to make any practical difference but there > > are drivers doing that for correctness. > > Why do you think that might not cause any issue ? After first message > is completed and ISR is executed, the completion flag remains done for > ever. Hi Sudeep,
I don't think that is the case; the bottom routine, do_wait_for_common(), decrements the x->done after a completion (which does an increment). Regardless, I think it is prudent to add the reinit patch you've provided below. BTW, one thing I could have done was incorporate the timeout value but I thought that since this is the "fast" call we shouldn't be timing out at all. Thanks much, Jim Quinlan Broadcom STB So practically 2nd message onwards won't block in wait_for_completion > which means return from smc/hvc is actually completion too which is clearly > wrong or am I missing something ? > > Jim, please confirm either way. If you agree I can add the below snippet, > no need to repost. > > Regards, > Sudeep > > -- > diff --git i/drivers/firmware/arm_scmi/smc.c w/drivers/firmware/arm_scmi/smc.c > index fd41d436e34b..86eac0831d3c 100644 > --- i/drivers/firmware/arm_scmi/smc.c > +++ w/drivers/firmware/arm_scmi/smc.c > @@ -144,6 +145,8 @@ static int smc_send_message(struct scmi_chan_info *cinfo, > > shmem_tx_prepare(scmi_info->shmem, xfer); > > + if (scmi_info->irq) > + reinit_completion(&scmi_info->tx_complete); > arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res); > if (scmi_info->irq) > wait_for_completion(&scmi_info->tx_complete); > > > This electronic communication and the information and any files transmitted > with it, or attached to it, are confidential and are intended solely for the > use of the individual or entity to whom it is addressed and may contain > information that is confidential, legally privileged, protected by privacy > laws, or otherwise restricted from disclosure to anyone else. If you are not > the intended recipient or the person responsible for delivering the e-mail to > the intended recipient, you are hereby notified that any use, copying, > distributing, dissemination, forwarding, printing, or copying of this e-mail > is strictly prohibited. If you received this e-mail in error, please return > the e-mail to the sender, delete it from your computer, and destroy any > printed copy of it.
