linux-kernel - Re: [PATCH] remoteproc: xlnx: avoid RPU force power down

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Message-ID: <CANLsYkzDCy1QWY23uwVz_35tjdUdATqc66QA=sp5=gSY2vUnRQ@mail.gmail.com>
Date: Tue, 22 Apr 2025 11:49:38 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: tanmay.shah@....com
Cc: andersson@...nel.org, linux-remoteproc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] remoteproc: xlnx: avoid RPU force power down

On Tue, 22 Apr 2025 at 10:10, Tanmay Shah <tanmay.shah@....com> wrote:
>
>
>
> On 4/22/25 10:59 AM, Mathieu Poirier wrote:
> > Good morning,
> >
> > On Mon, Apr 14, 2025 at 11:46:01AM -0700, Tanmay Shah wrote:
> >> Powering off RPU using force_pwrdwn call results in system failure
> >> if there are multiple users of that RPU node. Better mechanism is to use
> >> request_node and release_node EEMI calls. With use of these EEMI calls,
> >> platform management controller will take-care of powering off RPU
> >> when there is no user.
> >>
> >> Signed-off-by: Tanmay Shah <tanmay.shah@....com>
> >> ---
> >>   drivers/remoteproc/xlnx_r5_remoteproc.c | 29 ++++++++++++++++++++++++-
> >>   1 file changed, 28 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/remoteproc/xlnx_r5_remoteproc.c b/drivers/remoteproc/xlnx_r5_remoteproc.c
> >> index 5aeedeaf3c41..3597359c0fc8 100644
> >> --- a/drivers/remoteproc/xlnx_r5_remoteproc.c
> >> +++ b/drivers/remoteproc/xlnx_r5_remoteproc.c
> >> @@ -380,6 +380,18 @@ static int zynqmp_r5_rproc_start(struct rproc *rproc)
> >>      dev_dbg(r5_core->dev, "RPU boot addr 0x%llx from %s.", rproc->bootaddr,
> >>              bootmem == PM_RPU_BOOTMEM_HIVEC ? "OCM" : "TCM");
> >>
> >> +    /* Request node before starting RPU core if new version of API is supported */
> >> +    if (zynqmp_pm_feature(PM_REQUEST_NODE) > 1) {
> >> +            ret = zynqmp_pm_request_node(r5_core->pm_domain_id,
> >> +                                         ZYNQMP_PM_CAPABILITY_ACCESS, 0,
> >> +                                         ZYNQMP_PM_REQUEST_ACK_BLOCKING);
> >> +            if (ret < 0) {
> >> +                    dev_err(r5_core->dev, "failed to request 0x%x",
> >> +                            r5_core->pm_domain_id);
> >> +                    return ret;
> >> +            }
> >> +    }
> >> +
> >>      ret = zynqmp_pm_request_wake(r5_core->pm_domain_id, 1,
> >>                                   bootmem, ZYNQMP_PM_REQUEST_ACK_NO);
> >>      if (ret)
> >> @@ -401,10 +413,25 @@ static int zynqmp_r5_rproc_stop(struct rproc *rproc)
> >>      struct zynqmp_r5_core *r5_core = rproc->priv;
> >>      int ret;
> >>
> >> +    /* Use release node API to stop core if new version of API is supported */
> >> +    if (zynqmp_pm_feature(PM_RELEASE_NODE) > 1) {
> >> +            ret = zynqmp_pm_release_node(r5_core->pm_domain_id);
> >> +            if (ret)
> >> +                    dev_err(r5_core->dev, "failed to stop remoteproc RPU %d\n", ret);
> >> +            return ret;
> >> +    }
> >> +
> >> +    if (zynqmp_pm_feature(PM_FORCE_POWERDOWN) < 1) {
> >> +            dev_dbg(r5_core->dev, "EEMI interface %d not supported\n",
> >> +                    PM_FORCE_POWERDOWN);
> >> +            return -EOPNOTSUPP;
> >> +    }
> >
> > Here I have to guess, because it is not documented, that it is the check to see
> > if zynqmp_pm_force_pwrdwn() is available.  I'm not sure why it is needed because
> > zynqmp_pm_force_pwrdwn() returns and error code.
> >
> Hello,
>
> Thanks for reviews. Yes you are correct. Actually instead, the check
> should be for version 1 of PM_FORCE_POWER_DOWN. If version 1 is
> supported, only then execute the call otherwise print the error.
> Hence, the check should be something like:
>
> if (zynqmp_pm_feature(PM_FORCE_POWERDOWN) != 1) {
>         error out.
> }
>

The above still doesn't answer my question, i.e _why_ is a check
needed when zynqmp_pm_force_pwrdwn() returns an error code?  To me, if
something happens in zynqmp_pm_force_pwrdwn() then an error code is
reported and the current implementation is able to deal with it.

> I will fix and add comment as well.
>
> > Thanks,
> > Mathieu
> >
> >> +
> >> +    /* maintain force pwr down for backward compatibility */
> >>      ret = zynqmp_pm_force_pwrdwn(r5_core->pm_domain_id,
> >>                                   ZYNQMP_PM_REQUEST_ACK_BLOCKING);
> >>      if (ret)
> >> -            dev_err(r5_core->dev, "failed to stop remoteproc RPU %d\n", ret);
> >> +            dev_err(r5_core->dev, "core force power down failed\n");
> >>
> >>      return ret;
> >>   }
> >>
> >> base-commit: 8532691d0a85ab2a826808207e904f7d62a9d804
> >> --
> >> 2.34.1
> >>
>