linux-kernel - Re: [PATCH] remoteproc: Add support for predefined notifyids

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Date:   Wed, 15 Jan 2020 16:11:03 +0100 (CET)
From:   Clément Leger <cleger@...ray.eu>
To:     Arnaud Pouliquen <arnaud.pouliquen@...com>
Cc:     Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-remoteproc <linux-remoteproc@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] remoteproc: Add support for predefined notifyids



----- On 15 Jan, 2020, at 16:09, Arnaud Pouliquen arnaud.pouliquen@...com wrote:

> On 1/15/20 3:28 PM, Clément Leger wrote:
>> Hi Arnaud,
>> 
>> ----- On 15 Jan, 2020, at 15:06, Arnaud Pouliquen arnaud.pouliquen@...com wrote:
>> 
>>> Hi Clément,
>>>
>>> On 1/15/20 11:21 AM, Clement Leger wrote:
>>>> In order to support preallocated notify ids, if their value is
>>>> equal to FW_RSC_NOTIFY_ID_ANY, then do no allocate a notify id
>>>> dynamically but try to allocate the requested one. This is useful when
>>>> using custom ids to bind them to custom vendor resources. For instance,
>>>> it allow to assign a group of queues to a specific interrupti in order
>>>> to dispatch notifications.
>>>>
>>>> Signed-off-by: Clement Leger <cleger@...ray.eu>
>>>> ---
>>>>  drivers/remoteproc/remoteproc_core.c | 27 +++++++++++++++++++--------
>>>>  include/linux/remoteproc.h           |  1 +
>>>>  2 files changed, 20 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/remoteproc/remoteproc_core.c
>>>> b/drivers/remoteproc/remoteproc_core.c
>>>> index 307df98347ba..b1485fcd0f11 100644
>>>> --- a/drivers/remoteproc/remoteproc_core.c
>>>> +++ b/drivers/remoteproc/remoteproc_core.c
>>>> @@ -351,14 +351,27 @@ int rproc_alloc_vring(struct rproc_vdev *rvdev, int i)
>>>>  	/*
>>>>  	 * Assign an rproc-wide unique index for this vring
>>>>  	 * TODO: assign a notifyid for rvdev updates as well
>>>> -	 * TODO: support predefined notifyids (via resource table)
>>>>  	 */
>>>> -	ret = idr_alloc(&rproc->notifyids, rvring, 0, 0, GFP_KERNEL);
>>>> -	if (ret < 0) {
>>>> -		dev_err(dev, "idr_alloc failed: %d\n", ret);
>>>> -		return ret;
>>>> +	if (rsc->vring[i].notifyid == FW_RSC_NOTIFY_ID_ANY) {
>>>> +		ret = idr_alloc(&rproc->notifyids, rvring, 0, 0, GFP_KERNEL);
>>>> +		if (ret < 0) {
>>>> +			dev_err(dev, "idr_alloc failed: %d\n", ret);
>>>> +			return ret;
>>>> +		}
>>>> +		notifyid = ret;
>>>> +
>>>> +		/* Let the rproc know the notifyid of this vring.*/
>>>> +		rsc->vring[i].notifyid = notifyid;
>>>> +	} else {
>>>> +		/* Reserve requested notify_id */
>>>> +		notifyid = rsc->vring[i].notifyid;
>>>> +		ret = idr_alloc(&rproc->notifyids, rvring, notifyid,
>>>> +				notifyid + 1, GFP_KERNEL);
>>>> +		if (ret < 0) {
>>>> +			dev_err(dev, "idr_alloc failed: %d\n", ret);
>>>> +			return ret;
>>>> +		}
>>>>  	}
>>>> -	notifyid = ret;
>>>>  
>>>>  	/* Potentially bump max_notifyid */
>>>>  	if (notifyid > rproc->max_notifyid)
>>>> @@ -366,8 +379,6 @@ int rproc_alloc_vring(struct rproc_vdev *rvdev, int i)
>>>>  
>>>>  	rvring->notifyid = notifyid;
>>>>  
>>>> -	/* Let the rproc know the notifyid of this vring.*/
>>>> -	rsc->vring[i].notifyid = notifyid;
>>>>  	return 0;
>>>>  }
>>> The rproc_free_vring function resets the notifyid to -1 on free.
>>> This could generate a side effect if the resource table is not reloaded.
>> 
>> Oh indeed, I did not thought of that. What would you recommend ?
>> If using -1 in free vring, notify ids will be reallocated at next
>> round.
> Regarding the code i'm not sure that it is useful to reset the notifyID to -1 on
> free.
> In current version, on alloc, the notifyID is overwriten without check.
> And as vdev status is updated, vring struct in resource table should be
> considered as invalid
> Except if i missed a usecase/race condition...
> 
>> 
>> I was also worried that it would break some existing user applications
>> which uses "0" as a notify id in vring but expect the id to be
>> allocated dynamically. With my modification, it means it will try to
>> use "0" as a predefined id, leading to allocation failure.
>> 
> Yes this could introduce regression for firmware that sets 0 as default value.
> Probably better to introduce this patch with a new version of the resource table
> :)

Understood ;)

Regards,

Clément

> 
> Regards
> Arnaud
>>>
>>>>  
>>>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>>>> index 16ad66683ad0..dcae3394243e 100644
>>>> --- a/include/linux/remoteproc.h
>>>> +++ b/include/linux/remoteproc.h
>>>> @@ -123,6 +123,7 @@ enum fw_resource_type {
>>>>  };
>>>>  
>>>>  #define FW_RSC_ADDR_ANY (-1)
>>>> +#define FW_RSC_NOTIFY_ID_ANY (-1)This define can also be used in
>>>> rproc_free_vring
>> 
>> Indeed.
>> 
>> Thanks for your review.
>> 
>> Regards,
>> 
>> Clément
>> 
>>>
>>> Regards,
>>> Arnaud
>>>>  
>>>>  /**
> >>>   * struct fw_rsc_carveout - physically contiguous memory request