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Subject: Re: [PATCH v4 00/17] remoteproc: Add support for detaching a rproc
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
CC:     Arnaud POULIQUEN <arnaud.pouliquen@st.com>,
        "ohad@wizery.com" <ohad@wizery.com>,
        "bjorn.andersson@linaro.org" <bjorn.andersson@linaro.org>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "linux-remoteproc@vger.kernel.org" <linux-remoteproc@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20201218173228.2277032-1-mathieu.poirier@linaro.org>
 <64b559dc-9e89-c351-ddee-f9cebd155ed7@st.com>
 <20210202004956.GD1319650@xps15>
 <200a464a-f6dd-480c-d7cd-d8165828fabc@foss.st.com>
 <20210202224229.GA1541378@xps15>
From:   Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>
Message-ID: <0db646f7-a32b-f45f-5ddb-d1d23a54f30d@foss.st.com>
Date:   Wed, 3 Feb 2021 08:58:15 +0100
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On 2/2/21 11:42 PM, Mathieu Poirier wrote:
> On Tue, Feb 02, 2021 at 09:54:13AM +0100, Arnaud POULIQUEN wrote:
>>
>>
>> On 2/2/21 1:49 AM, Mathieu Poirier wrote:
>>> On Wed, Jan 27, 2021 at 10:21:24AM +0100, Arnaud POULIQUEN wrote:
>>>> Hi Mathieu
>>>>
>>>> On 12/18/20 6:32 PM, Mathieu Poirier wrote:
>>>>> Following the work done here [1], this set provides support for the
>>>>> remoteproc core to release resources associated with a remote processor
>>>>> without having to switch it off. That way a platform driver can be removed
>>>>> or the application processor power cycled while the remote processor is
>>>>> still operating.
>>>>>
>>>>> Of special interest in this series are patches 5 and 6 where getting the
>>>>> address of the resource table installed by an eternal entity if moved to
>>>>> the core.  This is to support scenarios where a remote process has been
>>>>> booted by the core but is being detached.  To re-attach the remote
>>>>> processor, the address of the resource table needs to be known at a later
>>>>> time than the platform driver's probe() function.
>>>>>
>>>>> Applies cleanly on v5.10
>>>>>
>>>>> Thanks,
>>>>> Mathieu
>>>>>
>>>>> [1]. https://lkml.org/lkml/2020/7/14/1600
>>>>>
>>>>> ----
>>>>> New for v4:
>>>>> - Made binding description OS agnostic (Rob)
>>>>> - Added functionality to set the external resource table in the core
>>>>> - Fixed a crash when detaching (Arnaud)
>>>>> - Fixed error code propagation in rproc_cdev_relase() and rproc_del() (Arnaud)
>>>>> - Added RB tags
>>>>
>>>>
>>>> I tested you series, attach and  detach is working well.
>>>>
>>>> Then I faced issue when tried to re-attach after a detach.
>>>>
>>>
>>> Right, in this case don't expect the re-attach to work properly because function
>>> stm32_rproc_detach() does not exist.  As such the M4 doesn't put itself back
>>> in "wait-for-attach" mode as it does when booted by the boot loader.  If I
>>> remember correctly we talked about that during an earlier conversation and we
>>> agreed FW support would be needed to properly test the re-attach.
>>
>> Yes you are right the remote firmware needs to be inform about the detach, and
>> this is the purpose of the detach ops.
>> But also some actions are missing on local side as some resources have also to
>> be reinitialized as described in my previous mail.
>> For instance the resource table is handled by the remoteproc framework. The
>> remote firmware should only have a read access to this table.
>>
>>>  
>>>> But I don't know if this feature has to be supported in this step.
>>>>
>>>> The 2 issues I found are:
>>>>
>>>> 1) memory carveouts are released on detach so need to be reinitialized.
>>>> The use of prepare/unprepare for the attach and detach would solve the issue but
>>>> probably need to add parameter to differentiate a start/stop from a attach/detach.
> 
> I am in agreement with you assesment and the patch you have proposed to fix it.
> Right now carveouts are properly handled between start and stop operations
> because their parsing and allocation is done as part for ops:parse_fw(), which
> is called for each iteration.  Moving the parsing and allocation to
> rproc_prepare_device() ends up doing the same thing.
> 
> I am not sure we absolutely need an extra parameter to differentiate between
> start/stop and attach/detach.  Typically the rproc_prepare_device() is used to
> do some kind of setup like providing power to a memory bank.  I suppose that if
> a memory bank is already powered by the boot loader, asking to power it up again
> won't do anything.
> 
> As such I suggest we keep the parameters as they are now.  We can revisit if a
> use case comes up at a later time. 
> 

Your suggestion sound good to me.

>>>>
>>>> 2) The vrings in the loaded resource table (so no cached) has to be properly
>>>> reinitialized. In rproc_free_vring  the vring da is set to 0 that is then
>>>> considered as a fixed address.
>>>>
>>>> Here is a fix which works on the stm32 platform
>>>>
>>>> @@ -425,7 +425,7 @@ void rproc_free_vring(struct rproc_vring *rvring)
>>>>  	 */
>>>>  	if (rproc->table_ptr) {
>>>>  		rsc = (void *)rproc->table_ptr + rvring->rvdev->rsc_offset;
>>>> -		rsc->vring[idx].da = 0;
>>>> +		rsc->vring[idx].da = FW_RSC_ADDR_ANY;
>>>>  		rsc->vring[idx].notifyid = -1;
>>>>  	}
>>>>  }
> 
> I see why this could be needed.  I initially assumed the remote processor would
> install a new resource table in memory upon receiving notification the core is
> going away.  But upon reflection the remote processor may not even have access
> to the image it is running.

The risk here is that both processors try to access this table at the same time.

> 
> Let me think about this further - I want to make sure we don't introduce a
> regression for current implementations.

Just a precision: the vring DA can be fixed by the coprocessor firmware to
impose the address, my patch is not sufficent in such case for the reattachment.
That's why i suggested a copy of the resource table before updating it.

Thanks,
Arnaud

> 
>>>
>>> In light of the above let me know if these two issues are still relevant.  If
>>> so I'll investigate further.
>>
>> To highlight the issue just test attach/detach/attch  with a firmware that
>> implements a RPMsg communication. On the second attach the virtio framework is
>> not properly restarted.
>>
>> Then please find at the end of the mail 3 patches for test I added on top of
>> your series,that allow me to reattach. Of course the RPMsg channels are not
>> re-created as i don't implement the remote FW part, but the Linux virtio and
>> RPmsg frameworks are restarted.
>>
>> - [PATCH 1/3] remoteproc: stm32: add capability to detach from the remoteproc
>>   => Add a dummy function in stm32_rproc for test.
>> - [PATCH 2/3] remoteproc: Add prepare/unprepare for attach detach
>>   => Add prepare/unprepare on attach/detach + implement attach in stm32mp1 to
>>      reinitialize the memory region that as been cleaned on detach.
>> - [PATCH 3/3] remoteproc: virtio: set to vring address to FW_RSC_ADDR_ANY on free
>>   => Reinitialize the vring addresses on detach. For this one a better
>>      implementation would be to use a cached resource table to fully
>>      reinitialize it on re-attach.
>>
>> Thanks,
>> Arnaud
>>
>>>
>>> Thanks,
>>> Mathieu
>>>
>>>>
>>>> Here, perhaps a better alternative would be to make a cached copy on attach
>>>> before updating it. On the next attach, the cached copy would be copied as it is
>>>> done in rproc_start.
>>>>
>>>> Thanks,
>>>> Arnaud
>>>>
>>>>
>>>>>
>>>>> Mathieu Poirier (17):
>>>>>   dt-bindings: remoteproc: Add bindind to support autonomous processors
>>>>>   remoteproc: Re-check state in rproc_shutdown()
>>>>>   remoteproc: Remove useless check in rproc_del()
>>>>>   remoteproc: Rename function rproc_actuate()
>>>>>   remoteproc: Add new get_loaded_rsc_table() remoteproc operation
>>>>>   remoteproc: stm32: Move resource table setup to rproc_ops
>>>>>   remoteproc: Add new RPROC_ATTACHED state
>>>>>   remoteproc: Properly represent the attached state
>>>>>   remoteproc: Properly deal with a kernel panic when attached
>>>>>   remoteproc: Add new detach() remoteproc operation
>>>>>   remoteproc: Introduce function __rproc_detach()
>>>>>   remoteproc: Introduce function rproc_detach()
>>>>>   remoteproc: Add return value to function rproc_shutdown()
>>>>>   remoteproc: Properly deal with a stop request when attached
>>>>>   remoteproc: Properly deal with a start request when attached
>>>>>   remoteproc: Properly deal with detach request
>>>>>   remoteproc: Refactor rproc delete and cdev release path
>>>>>
>>>>>  .../bindings/remoteproc/remoteproc-core.yaml  |  27 +++
>>>>>  drivers/remoteproc/remoteproc_cdev.c          |  32 ++-
>>>>>  drivers/remoteproc/remoteproc_core.c          | 211 +++++++++++++++---
>>>>>  drivers/remoteproc/remoteproc_internal.h      |   8 +
>>>>>  drivers/remoteproc/remoteproc_sysfs.c         |  20 +-
>>>>>  drivers/remoteproc/stm32_rproc.c              | 147 ++++++------
>>>>>  include/linux/remoteproc.h                    |  24 +-
>>>>>  7 files changed, 344 insertions(+), 125 deletions(-)
>>>>>  create mode 100644 Documentation/devicetree/bindings/remoteproc/remoteproc-core.yaml
>>>>>
>>
>> Subject: [PATCH 1/3] remoteproc: stm32: add capability to detach from the
>>  remoteproc
>>
>> Add a dummy function to allow to detach. No specific action is needed
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss-st.com>
>> ---
>>  drivers/remoteproc/stm32_rproc.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/remoteproc/stm32_rproc.c b/drivers/remoteproc/stm32_rproc.c
>> index 2c949725b91e..b325d28f627c 100644
>> --- a/drivers/remoteproc/stm32_rproc.c
>> +++ b/drivers/remoteproc/stm32_rproc.c
>> @@ -590,6 +590,12 @@ static int stm32_rproc_attach(struct rproc *rproc)
>>  	return reset_control_assert(ddata->hold_boot);
>>  }
>>
>> +static int stm32_rproc_detach(struct rproc *rproc)
>> +{
>> +	/* Nothing to do but ops mandatory to support the detach feature */
>> +	return 0;
>> +}
>> +
>>  static int stm32_rproc_stop(struct rproc *rproc)
>>  {
>>  	struct stm32_rproc *ddata = rproc->priv;
>> @@ -712,6 +718,7 @@ static struct rproc_ops st_rproc_ops = {
>>  	.start		= stm32_rproc_start,
>>  	.stop		= stm32_rproc_stop,
>>  	.attach		= stm32_rproc_attach,
>> +	.detach		= stm32_rproc_detach,
>>  	.kick		= stm32_rproc_kick,
>>  	.load		= rproc_elf_load_segments,
>>  	.parse_fw	= stm32_rproc_parse_fw,
>> -- 
>> 2.17.1
>>
>>
>> ------------------------------------------------------------------------
>>
>>
>> Subject: [PATCH 2/3] remoteproc: Add prepare/unprepare for attach detach
>>
>> Some actions such as memory resources reallocation are needed when try
>> to reattach. Use the prepare ops for these actions.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
>> ---
>>  drivers/remoteproc/remoteproc_core.c | 14 ++++++++++++++
>>  drivers/remoteproc/stm32_rproc.c     | 14 +++++++-------
>>  2 files changed, 21 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/remoteproc/remoteproc_core.c
>> b/drivers/remoteproc/remoteproc_core.c
>> index f1f51ad1a1d6..f177561b8863 100644
>> --- a/drivers/remoteproc/remoteproc_core.c
>> +++ b/drivers/remoteproc/remoteproc_core.c
>> @@ -1557,6 +1557,13 @@ static int rproc_attach(struct rproc *rproc)
>>  		return ret;
>>  	}
>>
>> +	/* Prepare rproc for firmware loading if needed */
>> +	ret = rproc_prepare_device(rproc);
>> +	if (ret) {
>> +		dev_err(dev, "can't prepare rproc %s: %d\n", rproc->name, ret);
>> +		goto disable_iommu;
>> +	}
>> +
>>  	ret = rproc_get_loaded_rsc_table(rproc);
>>  	if (ret) {
>>  		dev_err(dev, "can't load resource table: %d\n", ret);
>> @@ -1990,6 +1997,13 @@ int rproc_detach(struct rproc *rproc)
>>  	/* clean up all acquired resources */
>>  	rproc_resource_cleanup(rproc);
>>
>> +	/* Release HW resources if needed */
>> +	ret = rproc_unprepare_device(rproc);
>> +	if (ret) {
>> +		atomic_inc(&rproc->power);
>> +		goto out;
>> +	}
>> +
>>  	rproc_disable_iommu(rproc);
>>
>>  	/*
>> diff --git a/drivers/remoteproc/stm32_rproc.c b/drivers/remoteproc/stm32_rproc.c
>> index b325d28f627c..bf50d79b1f09 100644
>> --- a/drivers/remoteproc/stm32_rproc.c
>> +++ b/drivers/remoteproc/stm32_rproc.c
>> @@ -413,9 +413,6 @@ static int stm32_rproc_parse_fw(struct rproc *rproc, const
>> struct firmware *fw)
>>  	struct stm32_rproc *ddata = rproc->priv;
>>  	int ret;
>>
>> -	ret  = stm32_rproc_parse_memory_regions(rproc);
>> -	if (ret)
>> -		return ret;
>>
>>  	if (ddata->trproc)
>>  		ret = rproc_tee_get_rsc_table(ddata->trproc);
>> @@ -580,6 +577,12 @@ static int stm32_rproc_start(struct rproc *rproc)
>>
>>  	return reset_control_assert(ddata->hold_boot);
>>  }
>> +static int stm32_rproc_prepare(struct rproc *rproc)
>> +{
>> +	dev_err(&rproc->dev, "%s: %d\n", __func__, __LINE__);
>> +
>> +	return stm32_rproc_parse_memory_regions(rproc);
>> +}
>>
>>  static int stm32_rproc_attach(struct rproc *rproc)
>>  {
>> @@ -717,6 +720,7 @@ static int stm32_rproc_get_loaded_rsc_table(struct rproc *rproc)
>>  static struct rproc_ops st_rproc_ops = {
>>  	.start		= stm32_rproc_start,
>>  	.stop		= stm32_rproc_stop,
>> +	.prepare	= stm32_rproc_prepare,
>>  	.attach		= stm32_rproc_attach,
>>  	.detach		= stm32_rproc_detach,
>>  	.kick		= stm32_rproc_kick,
>> @@ -921,10 +925,6 @@ static int stm32_rproc_probe(struct platform_device *pdev)
>>
>>  	if (state == M4_STATE_CRUN) {
>>  		rproc->state = RPROC_DETACHED;
>> -
>> -		ret = stm32_rproc_parse_memory_regions(rproc);
>> -		if (ret)
>> -			goto free_resources;
>>  	}
>>
>>  	rproc->has_iommu = false;
>> -- 
>> 2.17.1
>>
>>
>> ------------------------------------------------------------------------
>>
>> Subject: [PATCH 3/3] remoteproc: virtio: set to vring address to
>>  FW_RSC_ADDR_ANY on free
>>
>> The resource table vring structure is cleaned on free. But value is set
>> to 0. This value is considered as a valid address. Set the value
>> to  FW_RSC_ADDR_ANY instead.
>> This is needed to allow to reattach to an autonomous firmware.
>> An alternative would be to save the resource table before updating it.
>> On free the value would be reset to initial value.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
>> ---
>>  drivers/remoteproc/remoteproc_core.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/remoteproc/remoteproc_core.c
>> b/drivers/remoteproc/remoteproc_core.c
>> index f177561b8863..5b5de4db3981 100644
>> --- a/drivers/remoteproc/remoteproc_core.c
>> +++ b/drivers/remoteproc/remoteproc_core.c
>> @@ -425,7 +425,7 @@ void rproc_free_vring(struct rproc_vring *rvring)
>>  	 */
>>  	if (rproc->table_ptr) {
>>  		rsc = (void *)rproc->table_ptr + rvring->rvdev->rsc_offset;
>> -		rsc->vring[idx].da = 0;
>> +		rsc->vring[idx].da = FW_RSC_ADDR_ANY;
>>  		rsc->vring[idx].notifyid = -1;
>>  	}
>>  }
>> -- 
>> 2.17.1
>>
>>
>>
>>
>>
>>