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Date: Thu, 27 Jun 2019 10:09:03 +0100 From: Sudeep Holla <sudeep.holla@....com> To: Jassi Brar <jassisinghbrar@...il.com> Cc: Florian Fainelli <f.fainelli@...il.com>, Peng Fan <peng.fan@....com>, Rob Herring <robh+dt@...nel.org>, Mark Rutland <mark.rutland@....com>, ", Sascha Hauer" <kernel@...gutronix.de>, dl-linux-imx <linux-imx@....com>, Shawn Guo <shawnguo@...nel.org>, "festevam@...il.com" <festevam@...il.com>, Devicetree List <devicetree@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Andre Przywara <andre.przywara@....com>, "van.freenix@...il.com" <van.freenix@...il.com>, Sudeep Holla <sudeep.holla@....com> Subject: Re: [PATCH V2 2/2] mailbox: introduce ARM SMC based mailbox On Wed, Jun 26, 2019 at 01:27:41PM -0500, Jassi Brar wrote: > On Wed, Jun 26, 2019 at 11:44 AM Florian Fainelli <f.fainelli@...il.com> wrote: > > > > On 6/26/19 6:31 AM, Peng Fan wrote: > > >>> The firmware driver might not have func-id, such as SCMI/SCPI. > > >>> So add an optional func-id to let smc mailbox driver could > > >>> use smc SiP func id. > > >>> > > >> There is no end to conforming to protocols. Controller drivers should > > >> be written having no particular client in mind. > > > > > > If the func-id needs be passed from user, then the chan_id suggested > > > by Sudeep should also be passed from user, not in mailbox driver. > > > > > > Jassi, so from your point, arm_smc_send_data just send a0 - a6 > > > to firmware, right? > > > > > > Sudeep, Andre, Florian, > > > > > > What's your suggestion? SCMI not support, do you have > > > plan to add smc transport in SCMI? > > > > On the platforms that I work with, we have taken the liberty of > > implementing SCMI in our monitor firmware because the other MCU we use > > for dynamic voltage and frequency scaling did not have enough memory to > > support that and we still had the ability to make that firmware be > > trusted enough we could give it power management responsibilities. I > > would certainly feel more comfortable if the SCMI specification was > > amended to indicate that the Agent could be such a software entity, > > still residing on the same host CPU as the Platform(s), but if not, > > that's fine. > > > > This has lead us to implement a mailbox driver that uses a proprietary > > SMC call for the P2A path ("tx" channel) and the return being done via > > either that same SMC or through SGI. You can take a look at it in our > > downstream tree here actually: > > > > https://github.com/Broadcom/stblinux-4.9/blob/master/linux/drivers/mailbox/brcmstb-mailbox.c > > > > If we can get rid of our own driver and uses a standard SMC based > > mailbox driver that supports our use case that involves interrupts (we > > can always change their kind without our firmware/boot loader since FDT > > is generated from that component), that would be great. > > > static irqreturn_t brcm_isr(void) > { > mbox_chan_received_data(&chans[0], NULL); > return IRQ_HANDLED; > } > > Sorry, I fail to understand why the irq can't be moved inside the > client driver itself? There can't be more cost to it and there > definitely is no functionality lost. What if there are multiple clients ? And I assume you are referring to case like this where IRQ is not tied to the mailbox IP. -- Regards, Sudeep
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