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Date:   Mon, 8 Feb 2021 16:43:25 -0700
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>
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>
Subject: Re: [PATCH v4 00/17] remoteproc: Add support for detaching a rproc
Message-ID: <20210208234325.GA1582054@xps15>
References: <20201218173228.2277032-1-mathieu.poirier@linaro.org>
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 <20210202004956.GD1319650@xps15>
 <200a464a-f6dd-480c-d7cd-d8165828fabc@foss.st.com>
 <20210202224229.GA1541378@xps15>
 <0db646f7-a32b-f45f-5ddb-d1d23a54f30d@foss.st.com>
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On Wed, Feb 03, 2021 at 08:58:15AM +0100, Arnaud POULIQUEN wrote:
> 
> 
> 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.

I've been staring long and hard at this code and I don't see another way than
keeping a clean copy of the resource table as you mentionned above.  And
managing that table isn't trivial either.  I am working on a solution, something
that I should be able to publish by the end of the week.

Thanks,
Mathieu

> >>>>
> >>>> 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
> >>
> >>
> >>
> >>
> >>
> >>