Re: [PATCH v5 1/3] remoteproc: add support for co-processor loaded and booted before kernel

From: Mathieu Poirier
Date: Wed Feb 26 2020 - 19:56:58 EST

On Thu, 20 Feb 2020 at 14:40, Mathieu Poirier
<mathieu.poirier@xxxxxxxxxx> wrote:
>
> On Thu, 20 Feb 2020 at 02:35, Arnaud POULIQUEN <arnaud.pouliquen@xxxxxx> wrote:
> >
> >
> >
> > On 2/19/20 9:56 PM, Mathieu Poirier wrote:
> > > Hey Arnaud,
> > >
> > > On Tue, 18 Feb 2020 at 10:31, Arnaud POULIQUEN <arnaud.pouliquen@xxxxxx> wrote:
> > >>
> > >> Hi Mathieu, Bjorn,
> > >>
> > >> On 2/17/20 7:40 PM, Mathieu Poirier wrote:
> > >>> On Fri, 14 Feb 2020 at 09:33, Arnaud POULIQUEN <arnaud.pouliquen@xxxxxx> wrote:
> > >>>>
> > >>>> Hi Mathieu,
> > >>>>
> > >>>> On 2/13/20 9:08 PM, Mathieu Poirier wrote:
> > >>>>> Good day,
> > >>>>>
> > >>>>> On Tue, Feb 11, 2020 at 06:42:03PM +0100, Arnaud Pouliquen wrote:
> > >>>>>> From: Loic Pallardy <loic.pallardy@xxxxxx>
> > >>>>>>
> > >>>>>> Remote processor could boot independently or be loaded/started before
> > >>>>>> Linux kernel by bootloader or any firmware.
> > >>>>>> This patch introduces a new property in rproc core, named skip_fw_load,
> > >>>>>> to be able to allocate resources and sub-devices like vdev and to
> > >>>>>> synchronize with current state without loading firmware from file system.
> > >>>>>> It is platform driver responsibility to implement the right firmware
> > >>>>>> load ops according to HW specificities.
> > >>>>>>
> > >>>>>> Signed-off-by: Loic Pallardy <loic.pallardy@xxxxxx>
> > >>>>>> Acked-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > >>>>>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
> > >>>>>> ---
> > >>>>>> drivers/remoteproc/remoteproc_core.c | 67 ++++++++++++++++++++++------
> > >>>>>> include/linux/remoteproc.h | 2 +
> > >>>>>> 2 files changed, 55 insertions(+), 14 deletions(-)
> > >>>>>>
> > >>>>>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> > >>>>>> index 097f33e4f1f3..876b5420a32b 100644
> > >>>>>> --- a/drivers/remoteproc/remoteproc_core.c
> > >>>>>> +++ b/drivers/remoteproc/remoteproc_core.c
> > >>>>>> @@ -1358,8 +1358,19 @@ static int rproc_start(struct rproc *rproc, const struct firmware *fw)
> > >>>>>> return ret;
> > >>>>>> }
> > >>>>>>
> > >>>>>> -/*
> > >>>>>> - * take a firmware and boot a remote processor with it.
> > >>>>>> +/**
> > >>>>>> + * rproc_fw_boot() - boot specified remote processor according to specified
> > >>>>>> + * firmware
> > >>>>>> + * @rproc: handle of a remote processor
> > >>>>>> + * @fw: pointer on firmware to handle
> > >>>>>> + *
> > >>>>>> + * Handle resources defined in resource table, load firmware and
> > >>>>>> + * start remote processor.
> > >>>>>> + *
> > >>>>>> + * If firmware pointer fw is NULL, firmware is not handled by remoteproc
> > >>>>>> + * core, but under the responsibility of platform driver.
> > >>>>>> + *
> > >>>>>> + * Returns 0 on success, and an appropriate error value otherwise.
> > >>>>>> */
> > >>>>>> static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
> > >>>>>> {
> > >>>>>> @@ -1371,7 +1382,11 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
> > >>>>>> if (ret)
> > >>>>>> return ret;
> > >>>>>>
> > >>>>>> - dev_info(dev, "Booting fw image %s, size %zd\n", name, fw->size);
> > >>>>>> + if (fw)
> > >>>>>> + dev_info(dev, "Booting fw image %s, size %zd\n", name,
> > >>>>>> + fw->size);
> > >>>>>> + else
> > >>>>>> + dev_info(dev, "Synchronizing with preloaded co-processor\n");
> > >>>>>>
> > >>>>>> /*
> > >>>>>> * if enabling an IOMMU isn't relevant for this rproc, this is
> > >>>>>> @@ -1718,16 +1733,22 @@ static void rproc_crash_handler_work(struct work_struct *work)
> > >>>>>> * rproc_boot() - boot a remote processor
> > >>>>>> * @rproc: handle of a remote processor
> > >>>>>> *
> > >>>>>> - * Boot a remote processor (i.e. load its firmware, power it on, ...).
> > >>>>>> + * Boot a remote processor (i.e. load its firmware, power it on, ...) from
> > >>>>>> + * different contexts:
> > >>>>>> + * - power off
> > >>>>>> + * - preloaded firmware
> > >>>>>> + * - started before kernel execution
> > >>>>>> + * The different operations are selected thanks to properties defined by
> > >>>>>> + * platform driver.
> > >>>>>> *
> > >>>>>> - * If the remote processor is already powered on, this function immediately
> > >>>>>> - * returns (successfully).
> > >>>>>> + * If the remote processor is already powered on at rproc level, this function
> > >>>>>> + * immediately returns (successfully).
> > >>>>>> *
> > >>>>>> * Returns 0 on success, and an appropriate error value otherwise.
> > >>>>>> */
> > >>>>>> int rproc_boot(struct rproc *rproc)
> > >>>>>> {
> > >>>>>> - const struct firmware *firmware_p;
> > >>>>>> + const struct firmware *firmware_p = NULL;
> > >>>>>> struct device *dev;
> > >>>>>> int ret;
> > >>>>>>
> > >>>>>> @@ -1758,11 +1779,20 @@ int rproc_boot(struct rproc *rproc)
> > >>>>>>
> > >>>>>> dev_info(dev, "powering up %s\n", rproc->name);
> > >>>>>>
> > >>>>>> - /* load firmware */
> > >>>>>> - ret = request_firmware(&firmware_p, rproc->firmware, dev);
> > >>>>>> - if (ret < 0) {
> > >>>>>> - dev_err(dev, "request_firmware failed: %d\n", ret);
> > >>>>>> - goto downref_rproc;
> > >>>>>> + if (!rproc->skip_fw_load) {
> > >>>>>> + /* load firmware */
> > >>>>>> + ret = request_firmware(&firmware_p, rproc->firmware, dev);
> > >>>>>> + if (ret < 0) {
> > >>>>>> + dev_err(dev, "request_firmware failed: %d\n", ret);
> > >>>>>> + goto downref_rproc;
> > >>>>>> + }
> > >>>>>> + } else {
> > >>>>>> + /*
> > >>>>>> + * Set firmware name pointer to null as remoteproc core is not
> > >>>>>> + * in charge of firmware loading
> > >>>>>> + */
> > >>>>>> + kfree(rproc->firmware);
> > >>>>>> + rproc->firmware = NULL;
> > >>>>>
> > >>>>> If the MCU with pre-loaded FW crashes request_firmware() in
> > >>>>> rproc_trigger_recovery() will return an error and rproc_start()
> > >>>>> never called.
> > >>>>
> > >>>> Right, something is missing in the recovery function to prevent request_firmware call if skip_fw_load is set
> > >>>>
> > >>>> We also identify an issue if recovery fails:
> > >>>> In case of recovery issue the rproc state is RPROC_CRASHED, so that it is no more possible to load a new firmware from
> > >>>> user space.
> > >>>> This issue is not linked to this patchset. We have patches on our shelves for this.
> > >>>>
> > >>>>>> }
> > >>>>>>
> > >>>>>> ret = rproc_fw_boot(rproc, firmware_p);
> > >>>>>> @@ -1916,8 +1946,17 @@ int rproc_add(struct rproc *rproc)
> > >>>>>> /* create debugfs entries */
> > >>>>>> rproc_create_debug_dir(rproc);
> > >>>>>>
> > >>>>>> - /* if rproc is marked always-on, request it to boot */
> > >>>>>> - if (rproc->auto_boot) {
> > >>>>>> + if (rproc->skip_fw_load) {
> > >>>>>> + /*
> > >>>>>> + * If rproc is marked already booted, no need to wait
> > >>>>>> + * for firmware.
> > >>>>>> + * Just handle associated resources and start sub devices
> > >>>>>> + */
> > >>>>>> + ret = rproc_boot(rproc);
> > >>>>>> + if (ret < 0)
> > >>>>>> + return ret;
> > >>>>>> + } else if (rproc->auto_boot) {
> > >>>>>> + /* if rproc is marked always-on, request it to boot */
> > >>>>>
> > >>>>> I spent way too much time staring at this modification... I can't decide if a
> > >>>>> system where the FW has been pre-loaded should be considered "auto_boot".
> > >>>>> Indeed the result is the same, i.e the MCU is started at boot time without user
> > >>>>> intervention.
> > >>>>
> > >>>> The main difference is that the firmware is loaded by the Linux remote proc in case of auto-boot.
> > >>>> In auto-boot mode the remoteproc loads a firmware, on probe, with a specified name without any request from user space.
> > >>>> One constraint of this mode is that the file system has to be accessible before the rproc probe.
> > >>>
> > >>> Indeed, but in both cases the MCU is booted automatically. In one
> > >>> case the FW is loaded by the framework and in the other it is not. As
> > >>> such both scenarios are "auto_boot", they simply have different
> > >>> flavours.
> > >> Regarding your concerns i would like to propose an alternative that will answer to following use cases:
> > >>
> > >> In term of use cases we can start the remote proc firmware in following modes:
> > >> - auto boot with FW loading, resource table parsing and FW start/stop
> > >> - auto boot without FW loading, with FW resource table parsing and FW start/stop
> > >> - auto boot with FW attachment and resource table parsing
> > >> - boot on userspace request with FW loading, resource table parsing and FW start/stop
> > >> - boot on userspace request without FW loading, with FW resource table parsing and FW start/stop
> > >> - boot on userspace request with FW attachment and resource table parsing
> > >>
> > >> I considered the recovery covered by these use cases...
> > >>
> > >> I tried to concatenate all use case to determine the behavior of the core and platform driver:
> > >> - "auto-boot" used to decide if boot is from driver or user space request (independently from fw loading and live cycle management)
> > >> - "skip_fw_load" allows to determine if a firmware has to be loaded or not.
> > >> - remote Firmware live cycle (start,stop,...) are managed by the platform driver, it would have to determine the manage the remote proc depending on the mode detected.
> > >>
> > >> If i apply this for stm32mp1 driver:
> > >> normal boot( FW started on user space request):
> > >> - auto-boot = 0
> > >> - skip_fw_load = 0
> > >> FW loaded and started by the bootloader
> > >> - auto-boot = 1
> > >> - skip_firmware = 1;
> > >>
> > >> => on a stop: the "auto-boot" and "skip_firmware flag will be reset by the stm32rproc driver, to allow user space to load a new firmware or reste the system.
> > >> this is considered as a ack by Bjorn today, if you have an alternative please share.
> > >
> > > I wonder if we can achieve the same results without needing
> > > rproc::skip_fw_load... For cases where the FW would have been loaded
> > > and the MCU started by another entity we could simply set rproc->state
> > > = RPROC_RUNNING in the platform driver. That way when the MCU is
> > > stopped or crashes, there is no flag to reset, rproc->state is simply
> > > set correctly by the current code.
> > >
> > > I would also set auto_boot =1 in order to start the AP synchronisation
> > > as quickly as possible and add a check in rproc_trigger_auto_boot() to
> > > see if rproc->state == RPROC_RUNNING. If so simply call rproc_boot()
> > > where platform specific rproc_ops would be tailored to handle a
> > > running processor.
> >
> > Your proposal is interesting, what concerns me is that seems to work only
> > for a first start.
>
> Correct, my proposal will skip loading the MCU firmware only when
> Linux boots and MCU probed. I thought this was what your patchset is
> doing.
>
> > And calling rproc_boot, while state is RPROC_RUNNING seems
> > pretty strange for me.
>
> After sending my email I thought about spinning off a new function,
> something like rproc_sync() and call it instead of rproc_boot(). But
> none of that matters now that Peng has highlighted the need to handle
> late attach scenarios where the FW is never loaded by the remoteproc
> core.
>
> > Also, as Peng mentions in https://patchwork.kernel.org/patch/11390485/,
> > the need also exists to skip the load of the firmware on recovery.
> > How to manage ROM/XIP Firmwares, no handling of the FW code only management
> > of the live cycle (using sysfs, crash management ....)?
> >
>
> A very good question, and something I need to think about after
> reviewing Peng's patchset. I will get back to you.

After reviewing Peng's patches it became clear to me using if/else
statements will quickly become unmanageable - we need something
flexible that can scale. After spending a long time looking at what
TI, NXP and ST have done to address their specific needs I think a
solution is starting to take shape in my head. From here I think the
best way to proceed is for me to write a patchset that enacts those
ideas and sent it out for review, something that should take me around
2 weeks.

>
> > >
> > > In my opinion the above would represent the state of the MCU rather
> > > than the state of the FW used by the MCU. It would also provide an
> > > opening for supporting systems where the MCU is not the life cycle
> > > manager.
> > Not sure to catch your point here. By "above" you mention your proposal or mine?
>
> I was talking about the lines I wrote.
>
> > In my opinion, rproc->state already represents the MCU state
> > what seems missing is the FW state
> > Could you clarify what you mean by "systems where the MCU is not the life cycle
> > manager" MCU = rproc framework?
>
> Arrgghh... That's a brain bug on my side. It should have been AP, not MCU.
>
> >
> > Regards
> > Arnaud
> >
> > >
> > > Let me know what you think...
> > >
> > >>
> > >> I need to rework the patchset in consequence but i would appreciate your feedback on this proposal before, to be sure that i well interpreted your concerns...
> > >>
> > >> Regards,
> > >> Arnaud
> > >>
> > >>>
> > >>>> This is not necessary the case, even if EPROBE_DEFER is used. In this case the driver has to be build as kernel module.
> > >>>>
> > >>>> Thanks,
> > >>>> Arnaud
> > >>>>>
> > >>>>> I'd welcome other people's opinion on this.
> > >>>>>
> > >>>>>> ret = rproc_trigger_auto_boot(rproc);
> > >>>>>> if (ret < 0)
> > >>>>>> return ret;
> > >>>>>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> > >>>>>> index 16ad66683ad0..4fd5bedab4fa 100644
> > >>>>>> --- a/include/linux/remoteproc.h
> > >>>>>> +++ b/include/linux/remoteproc.h
> > >>>>>> @@ -479,6 +479,7 @@ struct rproc_dump_segment {
> > >>>>>> * @table_sz: size of @cached_table
> > >>>>>> * @has_iommu: flag to indicate if remote processor is behind an MMU
> > >>>>>> * @auto_boot: flag to indicate if remote processor should be auto-started
> > >>>>>> + * @skip_fw_load: remote processor has been preloaded before start sequence
> > >>>>>> * @dump_segments: list of segments in the firmware
> > >>>>>> * @nb_vdev: number of vdev currently handled by rproc
> > >>>>>> */
> > >>>>>> @@ -512,6 +513,7 @@ struct rproc {
> > >>>>>> size_t table_sz;
> > >>>>>> bool has_iommu;
> > >>>>>> bool auto_boot;
> > >>>>>> + bool skip_fw_load;
> > >>>>>> struct list_head dump_segments;
> > >>>>>> int nb_vdev;
> > >>>>>> };
> > >>>>>> --
> > >>>>>> 2.17.1
> > >>>>>>