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

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Message-ID: <7dba1e4c-a7b8-4e18-82a3-db2a7f4fbe5c@amd.com>
Date: Tue, 22 Apr 2025 13:30:08 -0500
From: Tanmay Shah <tanmay.shah@....com>
To: Mathieu Poirier <mathieu.poirier@...aro.org>
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 4/22/25 12:49 PM, Mathieu Poirier wrote:
> 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.
> 

PM_FORCE_POWERDOWN will print redundant error messages from firmware if 
called for feature that is not supported. By doing above version check, 
we are avoiding those unnecessary error/warning messages. Other than 
that, you are correct we don't need to do version check as 
PM_FORCE_POWERDOWN will send respective error code and we will fail 
here. But version check helps to differentiate between actual error log 
from firmware when call is expected to work.

>> 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
>>>>
>>