RE: [PATCH v3 1/1] remoteproc: add support for co-processor loaded and booted before kernel

[Loic PALLARDY]

Hi Mathieu,

> -----Original Message-----
> From: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Sent: jeudi 14 novembre 2019 19:19
> To: Loic PALLARDY <loic.pallardy@xxxxxx>
> Cc: bjorn.andersson@xxxxxxxxxx; ohad@xxxxxxxxxx; linux-
> remoteproc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Arnaud
> POULIQUEN <arnaud.pouliquen@xxxxxx>; benjamin.gaignard@xxxxxxxxxx;
> Fabien DESSENNE <fabien.dessenne@xxxxxx>; s-anna@xxxxxx
> Subject: Re: [PATCH v3 1/1] remoteproc: add support for co-processor
> loaded and booted before kernel
> 
> Hi Loic,
> 
> On Wed, Nov 13, 2019 at 10:29:03PM +0100, Loic Pallardy wrote:
> > 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>
> >
> > ---
> > Change from v2:
> > - rename property into skip_fw_load
> > - update rproc_boot and rproc_fw_boot description
> > - update commit message
> > Change from v1:
> > - Keep bool in struct rproc
> > ---
> >  drivers/remoteproc/remoteproc_core.c | 51
> +++++++++++++++++++++++++++---------
> >  include/linux/remoteproc.h           |  2 ++
> >  2 files changed, 40 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/remoteproc/remoteproc_core.c
> b/drivers/remoteproc/remoteproc_core.c
> > index 3c5fbbbfb0f1..585cdca8b241 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -1360,7 +1360,7 @@ static int rproc_start(struct rproc *rproc, const
> struct firmware *fw)
> >  }
> >
> >  /*
> > - * take a firmware and boot a remote processor with it.
> > + * Handle resources defined in resource table and start a remote
> processor.
> >   */
> >  static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
> >  {
> > @@ -1372,7 +1372,11 @@ 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");
> 
> Here we assume that if @fw is NULL then the image is already loaded.  The
> first
> question that comes to mind is if that means the ELF image has already been
> copied to the coprocessor's boot address.  If that is the case it would be nice
> to make it explicit with a comment in the code.

Yes, but will be better to test "skip_fw_load" properties to change display info message.
Anyway, agree to mention that if @fw is NULL that means fw considered as already loaded.
> 
> Following the earlier comments made on the thread for this serie, I
> understand
> the rproc_ops fed to the core should provision for @fw being NULL.  In
> this case though st_rproc_ops[1] reference a number of core operations that
> aren't tailored to handled a NULL @fw parameter.

True, some patches will follow

> 
> I am pretty sure you're well aware of this and you have more patches to go
> with
> this one or said patches have already been published and I'm looking at the
> wrong tree. If that is the case would you mind making those patches public or
> pointing me to a repository somewhere?

Please have a look here [1].
The properties is named preloaded instead of skip_fw_load, but that's the same.
Impacted ops are working differently according to preloaded status.

When skip_fw_load is true, no ELF image is used. Platform driver is in charge of providing resource table location somewhere in memory.
Somewhere is platform dependent.

Regards,
Loic
[1] https://github.com/STMicroelectronics/linux/blob/v4.19-stm32mp/drivers/remoteproc/stm32_rproc.c

> 
> I have other concerns about the specifics shared between the application
> and co
> processors using the ELF image but I'll wait for your reply to the above before
> addressing those.
> 
> Regards,
> Mathieu
> 
> [1]. https://elixir.bootlin.com/linux/v5.4-
> rc7/source/drivers/remoteproc/stm32_rproc.c#L470
> 
> >
> >  	/*
> >  	 * if enabling an IOMMU isn't relevant for this rproc, this is
> > @@ -1719,16 +1723,22 @@ 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;
> >
> > @@ -1759,11 +1769,17 @@ 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 to null as unknown */
> > +		kfree(rproc->firmware);
> > +		rproc->firmware = NULL;
> >  	}
> >
> >  	ret = rproc_fw_boot(rproc, firmware_p);
> > @@ -1917,8 +1933,17 @@ 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 */
> >  		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;
> >  };
> > --
> > 2.7.4
> >