linux-kernel - Re: [PATCH v3 03/14] remoteproc: Add new operation and flags for synchronistation

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Date:   Thu, 30 Apr 2020 13:49:31 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Arnaud POULIQUEN <arnaud.pouliquen@...com>
Cc:     bjorn.andersson@...aro.org, ohad@...ery.com, loic.pallardy@...com,
        s-anna@...com, linux-remoteproc@...r.kernel.org, corbet@....net,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 03/14] remoteproc: Add new operation and flags for
 synchronistation

On Tue, Apr 28, 2020 at 06:38:41PM +0200, Arnaud POULIQUEN wrote:
> 
> 
> On 4/24/20 10:01 PM, Mathieu Poirier wrote:
> > Add a new sync_ops to support use cases where the remoteproc
> > core is synchronising with the remote processor.  Exactly when to use
> > the synchronisation operations is directed by the flags in structure
> > rproc_sync_flags.
> > 
> > Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> > ---
> >  include/linux/remoteproc.h | 24 ++++++++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> > 
> > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> > index ac4082f12e8b..ceb3b2bba824 100644
> > --- a/include/linux/remoteproc.h
> > +++ b/include/linux/remoteproc.h
> > @@ -353,6 +353,23 @@ enum rsc_handling_status {
> >  	RSC_IGNORED	= 1,
> >  };
> >  
> > +/**
> > + * struct rproc_sync_flags - platform specific flags indicating which
> > + *			      rproc_ops to use at specific times during
> > + *			      the rproc lifecycle.
> > + * @on_init: true if synchronising with the remote processor at
> > + *	     initialisation time
> > + * @after_stop: true if synchronising with the remote processor after it was
> > + *		stopped from the cmmand line
> typo command
> > + * @after_crash: true if synchronising with the remote processor after
> > + *		 it has crashed
> > + */
> > +struct rproc_sync_flags {
> > +	bool on_init;
> > +	bool after_stop;
> > +	bool after_crash;
> > +};
> > +
> how about a bit field instead (just a proposition)?
> Platform driver would set the sync flag and rproc_set_sync_flag could be a 
> simple mask instead of a switch case.

I opted for a structure over bit fields because I thought it would be easier to
read/understand.  Both approaches are valid and I have to particular preference
other than, in my own view, a structure is easier to understand.  

I'll wait a little to see what other people think.  If nobody objects the next
revision will have bit fields.

> 
> Is it possible to split this patch in a different ways because difficult to understand as
> rproc_sync_flags seems not used before 
> [PATCH v3 09/14] remoteproc: Deal with synchronisation when crashing

Certainly

> 
> Thanks
> Arnaud  
> 
> >  /**
> >   * struct rproc_ops - platform-specific device handlers
> >   * @start:	power on the device and boot it
> > @@ -459,6 +476,9 @@ struct rproc_dump_segment {
> >   * @firmware: name of firmware file to be loaded
> >   * @priv: private data which belongs to the platform-specific rproc module
> >   * @ops: platform-specific start/stop rproc handlers
> > + * @sync_ops: platform-specific start/stop rproc handlers when
> > + *	      synchronising with a remote processor.
> > + * @sync_flags: Determine the rproc_ops to choose in specific states.
> >   * @dev: virtual device for refcounting and common remoteproc behavior
> >   * @power: refcount of users who need this rproc powered up
> >   * @state: state of the device
> > @@ -482,6 +502,7 @@ 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
> > + * @sync_with_rproc: true if currently synchronising with the rproc
> >   * @dump_segments: list of segments in the firmware
> >   * @nb_vdev: number of vdev currently handled by rproc
> >   */
> > @@ -492,6 +513,8 @@ struct rproc {
> >  	const char *firmware;
> >  	void *priv;
> >  	struct rproc_ops *ops;
> > +	struct rproc_ops *sync_ops;
> > +	struct rproc_sync_flags sync_flags;
> >  	struct device dev;
> >  	atomic_t power;
> >  	unsigned int state;
> > @@ -515,6 +538,7 @@ struct rproc {
> >  	size_t table_sz;
> >  	bool has_iommu;
> >  	bool auto_boot;
> > +	bool sync_with_rproc;
> >  	struct list_head dump_segments;
> >  	int nb_vdev;
> >  	u8 elf_class;
> >