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

From: Mathieu Poirier
Date: Thu Feb 20 2020 - 16:40:32 EST

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.

> >
> > 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
> >>>>>>