[PATCH 2/2] firmware: arm_scmi: Add compatibility checks for shmem node

[Sudeep Holla]

On Thu, Jun 03, 2021 at 10:20:32AM -0700, Florian Fainelli wrote:
> On 6/3/21 10:18 AM, Florian Fainelli wrote:
> > On 6/2/21 12:53 AM, Sudeep Holla wrote:
> >> On Wed, Jun 02, 2021 at 09:44:40AM +0200, Etienne Carriere wrote:
> >>> On Wed, 2 Jun 2021 at 09:37, Sudeep Holla <sudeep.holla at arm.com> wrote:
> >>>>
> >>>> On Wed, Jun 02, 2021 at 09:33:03AM +0200, Etienne Carriere wrote:
> >>>>> Hello Sudeep,
> >>>>>
> >>>>>
> >>>>> On Wed, 2 Jun 2021 at 00:51, Sudeep Holla <sudeep.holla at arm.com> wrote:
> >>>>>>
> >>>>>> The shared memory node used for communication between the firmware and
> >>>>>> the OS should be compatible with "arm,scmi-shmem". Add the check for the
> >>>>>> same while parsing the node before fetching the memory regions.
> >>>>>>
> >>>>>> Cc: Cristian Marussi <cristian.marussi at arm.com>
> >>>>>> Cc: Florian Fainelli <f.fainelli at gmail.com>
> >>>>>> Cc: Jim Quinlan <jim2101024 at gmail.com>
> >>>>>> Cc: Etienne Carriere <etienne.carriere at linaro.org>
> >>>>>> Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
> >>>>>> ---
> >>>>>>  drivers/firmware/arm_scmi/mailbox.c | 3 +++
> >>>>>>  drivers/firmware/arm_scmi/smc.c     | 3 +++
> >>>>>>  2 files changed, 6 insertions(+)
> >>>>>>
> >>>>>> diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c
> >>>>>> index 4626404be541..e3dcb58314ae 100644
> >>>>>> --- a/drivers/firmware/arm_scmi/mailbox.c
> >>>>>> +++ b/drivers/firmware/arm_scmi/mailbox.c
> >>>>>> @@ -69,6 +69,9 @@ static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
> >>>>>>                 return -ENOMEM;
> >>>>>>
> >>>>>>         shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
> >>>>>> +       if (!of_device_is_compatible(shmem, "arm,scmi-shmem"))
> >>>>>> +               return -ENXIO;
> >>>>>
> >>>>> Before this change, one could use another type of memory node, like "mmio-sram".
> >>>>> Is there a strong reason to enforce use of "arm,scmi-shmem" nodes?
> >>>>>
> >>>>
> >>>> No that is for the entire SRAM which still holds and generic on-chip SRAM
> >>>> driver will take care of that, this is only for the subsections that is
> >>>> reserved for the scp shmem. The binding has been always there, just the
> >>>> missing check. When I move to yaml, I realised that and hence the
> >>>> addition of check.
> >>>
> >>> Ok, I understand. True the binding was there but only in the DTS
> >>> examples snipped.
> >>> This constraint on the compatible property of the shmem node should be
> >>> clearly stated in the yaml I think.
> >>>
> >>
> >> Was this missing in your DTS files ? Just curious.
> >>
> > 
> > FWIW, our legacy DTs would have the following:
> > 
> > 	reserved-memory {
> >                 /* This is a placeholder */
> >                 NWMBOX: NWMBOX {
> >                 };
> >         };
> > 
> >        brcm_scmi: brcm_scmi at 0 {
> >                 compatible = "arm,scmi-smc", "arm,scmi";
> >                 mboxes = <&brcm_scmi_mailbox 0>, <&brcm_scmi_mailbox 1>;
> >                 mbox-names = "tx", "rx";
> >                 shmem = <&NWMBOX>;
> >                 status = "disabled";
> > 
> > so while we have since switched to the SMC transport, the shared memory
> > still does not have an "arm,scmi-shmem" compatible string, and this is a
> > relatively new thing, so I am not sure we can enforce that just yet?
> 
> Sorry, I incorrectly browsed the binding history, this is not a new
> requirement,  will make sure we fix it at our end, too.

Indeed, I cross checked that when I hit the issue on Juno yesterday.
Anyways this version has build issues, was sent by mistake. I have resend
the correct ones later[1]

-- 
Regards,
Sudeep

[1] https://lore.kernel.org/r/20210602073851.1005607-2-sudeep.holla@arm.com/