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SubjectRe: [PATCH v5 1/3] remoteproc: add support for co-processor loaded and booted before kernel
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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@st.com> 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@st.com>
>>>>
>>>> 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@st.com>
>>>> Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>>>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
>>>> ---
>>>> 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 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
>>>>

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