Subject: Re: [RFC PATCH v2 1/6] remoteproc: core: Introduce virtio device
 add/remove functions
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
CC:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        <linux-remoteproc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>
References: <20211222082349.30378-1-arnaud.pouliquen@foss.st.com>
 <20211222082349.30378-2-arnaud.pouliquen@foss.st.com>
 <20220104190810.GB540353@p14s>
From:   Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>
Message-ID: <9f047c7b-a91c-9600-cdaf-7984ad7666f3@foss.st.com>
Date:   Wed, 5 Jan 2022 09:05:21 +0100
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Hello Mathieu,

On 1/4/22 8:08 PM, Mathieu Poirier wrote:
> Good morning,
> 
> On Wed, Dec 22, 2021 at 09:23:44AM +0100, Arnaud Pouliquen wrote:
>> In preparation of the migration of the management of rvdev in
>> remoteproc_virtio.c, this patch spins off new functions to manage the
>> remoteproc virtio device.
>>
>> The rproc_rvdev_add_device and rproc_rvdev_remove_device will be
>> moved to remoteproc_virtio.c.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
>> ---
>> update vs previous revision:
>>   - update according to the rebase from v15-rc1 to v16-rc1
>>   - split patch to introduce rproc_register_rvdev and rproc_unregister_rvdev
>>     function in a separate patch
>> ---
>>   drivers/remoteproc/remoteproc_core.c | 94 +++++++++++++++++-----------
>>   1 file changed, 57 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>> index 69f51acf235e..d1f1c5c25bd7 100644
>> --- a/drivers/remoteproc/remoteproc_core.c
>> +++ b/drivers/remoteproc/remoteproc_core.c
>> @@ -484,6 +484,61 @@ static int copy_dma_range_map(struct device *to, struct device *from)
>>   	return 0;
>>   }
>>   
>> +static int rproc_rvdev_add_device(struct rproc_vdev *rvdev)
>> +{
>> +	struct rproc *rproc = rvdev->rproc;
>> +	char name[16];
>> +	int ret;
>> +
>> +	snprintf(name, sizeof(name), "vdev%dbuffer", rvdev->index);
>> +	rvdev->dev.parent = &rproc->dev;
>> +	rvdev->dev.release = rproc_rvdev_release;
>> +	dev_set_name(&rvdev->dev, "%s#%s", dev_name(rvdev->dev.parent), name);
>> +	dev_set_drvdata(&rvdev->dev, rvdev);
>> +
>> +	ret = device_register(&rvdev->dev);
>> +	if (ret) {
>> +		put_device(&rvdev->dev);
>> +		return ret;
>> +	}
> 
> Registering the device here is a problem...  If device_register() fails
> put_device() is called and we return, only to call device_unregister() on the
> same device in rproc_handle_vdev().
> 
> Moreover in rproc_handle_vdev(), device_unregister() is called in the error
> path but device_register() is called here in rproc_rvdev_add_device().  This
> introduces coupling between the two functions, making it hard to maintain from
> hereon.

Very relevant, I need to rework the error management.

> 
> I suggest calling device_register() in rproc_handle_vdev() after
> rproc_rvdev_add_device() has returned successfully.

One of the goals of this patchset is to move the device_register in 
remote_proc_virtio.c
Doing this would not go in this direction.

I need to test but following could be an alternative:
- Call rproc_rvdev_remove_device in rproc_handle_vdev in case of error.
- Remove the put_device in rproc_rvdev_add_device.

=> This would be aligned with patch [6/6] implementation
with rproc_virtio_register_device/rproc_virtio_unregister_device...

Thanks,
Arnaud

> 
> More comments to come tomorrow.
> 
> Thanks,
> Mathieu
> 
>> +	ret = copy_dma_range_map(&rvdev->dev, rproc->dev.parent);
>> +	if (ret)
>> +		goto free_rvdev;
>> +
>> +	/* Make device dma capable by inheriting from parent's capabilities */
>> +	set_dma_ops(&rvdev->dev, get_dma_ops(rproc->dev.parent));
>> +
>> +	ret = dma_coerce_mask_and_coherent(&rvdev->dev,
>> +					   dma_get_mask(rproc->dev.parent));
>> +	if (ret) {
>> +		dev_warn(&rvdev->dev,
>> +			 "Failed to set DMA mask %llx. Trying to continue... (%pe)\n",
>> +			 dma_get_mask(rproc->dev.parent), ERR_PTR(ret));
>> +	}
>> +
>> +	list_add_tail(&rvdev->node, &rproc->rvdevs);
>> +
>> +	rvdev->subdev.start = rproc_vdev_do_start;
>> +	rvdev->subdev.stop = rproc_vdev_do_stop;
>> +
>> +	rproc_add_subdev(rproc, &rvdev->subdev);
>> +
>> +	return 0;
>> +
>> +free_rvdev:
>> +	device_unregister(&rvdev->dev);
>> +	return ret;
>> +}
>> +
>> +static void rproc_rvdev_remove_device(struct rproc_vdev *rvdev)
>> +{
>> +	struct rproc *rproc = rvdev->rproc;
>> +
>> +	rproc_remove_subdev(rproc, &rvdev->subdev);
>> +	list_del(&rvdev->node);
>> +	device_unregister(&rvdev->dev);
>> +}
>> +
>>   /**
>>    * rproc_handle_vdev() - handle a vdev fw resource
>>    * @rproc: the remote processor
>> @@ -519,7 +574,6 @@ static int rproc_handle_vdev(struct rproc *rproc, void *ptr,
>>   	struct device *dev = &rproc->dev;
>>   	struct rproc_vdev *rvdev;
>>   	int i, ret;
>> -	char name[16];
>>   
>>   	/* make sure resource isn't truncated */
>>   	if (struct_size(rsc, vring, rsc->num_of_vrings) + rsc->config_len >
>> @@ -553,34 +607,10 @@ static int rproc_handle_vdev(struct rproc *rproc, void *ptr,
>>   	rvdev->rproc = rproc;
>>   	rvdev->index = rproc->nb_vdev++;
>>   
>> -	/* Initialise vdev subdevice */
>> -	snprintf(name, sizeof(name), "vdev%dbuffer", rvdev->index);
>> -	rvdev->dev.parent = &rproc->dev;
>> -	rvdev->dev.release = rproc_rvdev_release;
>> -	dev_set_name(&rvdev->dev, "%s#%s", dev_name(rvdev->dev.parent), name);
>> -	dev_set_drvdata(&rvdev->dev, rvdev);
>> -
>> -	ret = device_register(&rvdev->dev);
>> -	if (ret) {
>> -		put_device(&rvdev->dev);
>> -		return ret;
>> -	}
>> -
>> -	ret = copy_dma_range_map(&rvdev->dev, rproc->dev.parent);
>> +	ret = rproc_rvdev_add_device(rvdev);
>>   	if (ret)
>>   		goto free_rvdev;
>>   
>> -	/* Make device dma capable by inheriting from parent's capabilities */
>> -	set_dma_ops(&rvdev->dev, get_dma_ops(rproc->dev.parent));
>> -
>> -	ret = dma_coerce_mask_and_coherent(&rvdev->dev,
>> -					   dma_get_mask(rproc->dev.parent));
>> -	if (ret) {
>> -		dev_warn(dev,
>> -			 "Failed to set DMA mask %llx. Trying to continue... (%pe)\n",
>> -			 dma_get_mask(rproc->dev.parent), ERR_PTR(ret));
>> -	}
>> -
>>   	/* parse the vrings */
>>   	for (i = 0; i < rsc->num_of_vrings; i++) {
>>   		ret = rproc_parse_vring(rvdev, rsc, i);
>> @@ -598,13 +628,6 @@ static int rproc_handle_vdev(struct rproc *rproc, void *ptr,
>>   			goto unwind_vring_allocations;
>>   	}
>>   
>> -	list_add_tail(&rvdev->node, &rproc->rvdevs);
>> -
>> -	rvdev->subdev.start = rproc_vdev_do_start;
>> -	rvdev->subdev.stop = rproc_vdev_do_stop;
>> -
>> -	rproc_add_subdev(rproc, &rvdev->subdev);
>> -
>>   	return 0;
>>   
>>   unwind_vring_allocations:
>> @@ -619,7 +642,6 @@ void rproc_vdev_release(struct kref *ref)
>>   {
>>   	struct rproc_vdev *rvdev = container_of(ref, struct rproc_vdev, refcount);
>>   	struct rproc_vring *rvring;
>> -	struct rproc *rproc = rvdev->rproc;
>>   	int id;
>>   
>>   	for (id = 0; id < ARRAY_SIZE(rvdev->vring); id++) {
>> @@ -627,9 +649,7 @@ void rproc_vdev_release(struct kref *ref)
>>   		rproc_free_vring(rvring);
>>   	}
>>   
>> -	rproc_remove_subdev(rproc, &rvdev->subdev);
>> -	list_del(&rvdev->node);
>> -	device_unregister(&rvdev->dev);
>> +	rproc_rvdev_remove_device(rvdev);
>>   }
>>   
>>   /**
>> -- 
>> 2.17.1
>>