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Subject: Re: [PATCH v3 12/14] remoteproc: Introducing function
 rproc_set_state_machine()
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
CC:     <bjorn.andersson@linaro.org>, <ohad@wizery.com>,
        <loic.pallardy@st.com>, <s-anna@ti.com>,
        <linux-remoteproc@vger.kernel.org>, <corbet@lwn.net>,
        <linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20200424200135.28825-1-mathieu.poirier@linaro.org>
 <20200424200135.28825-13-mathieu.poirier@linaro.org>
 <d297aeab-4f7e-95e0-04c0-266e0f08b2d0@st.com>
 <1438e3f6-3d8a-7edd-f552-b01f84316ec7@st.com> <20200430205143.GC18004@xps15>
From:   Arnaud POULIQUEN <arnaud.pouliquen@st.com>
Message-ID: <f686ac42-844b-d1c0-913a-c23f42834133@st.com>
Date:   Mon, 4 May 2020 14:00:45 +0200
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On 4/30/20 10:51 PM, Mathieu Poirier wrote:
> On Wed, Apr 29, 2020 at 04:38:54PM +0200, Arnaud POULIQUEN wrote:
>>
>>
>> On 4/29/20 11:22 AM, Arnaud POULIQUEN wrote:
>>>
>>>
>>> On 4/24/20 10:01 PM, Mathieu Poirier wrote:
>>>> Introducting function rproc_set_state_machine() to add
>>>> operations and a set of flags to use when synchronising with
>>>> a remote processor.
>>>>
>>>> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>>>> ---
>>>>  drivers/remoteproc/remoteproc_core.c     | 54 ++++++++++++++++++++++++
>>>>  drivers/remoteproc/remoteproc_internal.h |  6 +++
>>>>  include/linux/remoteproc.h               |  3 ++
>>>>  3 files changed, 63 insertions(+)
>>>>
>>>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>>>> index 48afa1f80a8f..5c48714e8702 100644
>>>> --- a/drivers/remoteproc/remoteproc_core.c
>>>> +++ b/drivers/remoteproc/remoteproc_core.c
>>>> @@ -2065,6 +2065,59 @@ int devm_rproc_add(struct device *dev, struct rproc *rproc)
>>>>  }
>>>>  EXPORT_SYMBOL(devm_rproc_add);
>>>>  
>>>> +/**
>>>> + * rproc_set_state_machine() - Set a synchronisation ops and set of flags
>>>> + *			       to use with a remote processor
>>>> + * @rproc:	The remote processor to work with
>>>> + * @sync_ops:	The operations to use when synchronising with a remote
>>>> + *		processor
>>>> + * @sync_flags:	The flags to use when deciding if the remoteproc core
>>>> + *		should be synchronising with a remote processor
>>>> + *
>>>> + * Returns 0 on success, an error code otherwise.
>>>> + */
>>>> +int rproc_set_state_machine(struct rproc *rproc,
>>>> +			    const struct rproc_ops *sync_ops,
>>>> +			    struct rproc_sync_flags sync_flags)
>>>
>>> So this API should be called by platform driver only in case of synchronization
>>> support, right?
>>> In this case i would rename it as there is also a state machine in "normal" boot
>>> proposal: rproc_set_sync_machine or rproc_set_sync_state_machine
>>>
>>
>> Reviewing the stm32 series, i wonder if sync_flags should be a pointer to a const structure
>> as the platform driver should not update it during the rproc live cycle.
>> Then IMO, using a pointer to the structure instead of the structure seems more 
>> in line with the rest of the remoteproc API.
> 
> Humm... If we do make sync_flags constant then the platform drivers can't modify
> the values dynamically, as I did in the stm32 series.  This is something Loic
> had asked for.
> 
> Moreover function rproc_set_state_machine() can't be called twice so updating
> the sync_flags can't happen.

You are right, make it constant is not a good idea.

Regards,
Arnaud 
> 
>>
>>>> +{
>>>> +	if (!rproc || !sync_ops)
>>>> +		return -EINVAL;
>>>> +
>>>> +	/*
>>>> +	 * No point in going further if we never have to synchronise with
>>>> +	 * the remote processor.
>>>> +	 */
>>>> +	if (!sync_flags.on_init &&
>>>> +	    !sync_flags.after_stop && !sync_flags.after_crash)
>>>> +		return 0;
>>>> +
>>>> +	/*
>>>> +	 * Refuse to go further if remoteproc operations have been allocated
>>>> +	 * but they will never be used.
>>>> +	 */
>>>> +	if (rproc->ops && sync_flags.on_init &&
>>>> +	    sync_flags.after_stop && sync_flags.after_crash)
>>>> +		return -EINVAL;
>>>> +
>>>> +	/*
>>>> +	 * Don't allow users to set this more than once to avoid situations
>>>> +	 * where the remote processor can't be recovered.
>>>> +	 */
>>>> +	if (rproc->sync_ops)
>>>> +		return -EINVAL;
>>>> +
>>>> +	rproc->sync_ops = kmemdup(sync_ops, sizeof(*sync_ops), GFP_KERNEL);
>>>> +	if (!rproc->sync_ops)
>>>> +		return -ENOMEM;
>>>> +
>>>> +	rproc->sync_flags = sync_flags;
>>>> +	/* Tell the core what to do when initialising */
>>>> +	rproc_set_sync_flag(rproc, RPROC_SYNC_STATE_INIT);
>>>
>>> Is there a use case where sync_flags.on_init is false and other flags are true?
>>>
>>> Look like on_init is useless and should not be exposed to the platform driver.
>>> Or comments are missing to explain the usage of it vs the other flags.
>>>
>>> Regards,
>>> Arnaud
>>>  
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +EXPORT_SYMBOL(rproc_set_state_machine);
>>>> +
>>>>  /**
>>>>   * rproc_type_release() - release a remote processor instance
>>>>   * @dev: the rproc's device
>>>> @@ -2088,6 +2141,7 @@ static void rproc_type_release(struct device *dev)
>>>>  	kfree_const(rproc->firmware);
>>>>  	kfree_const(rproc->name);
>>>>  	kfree(rproc->ops);
>>>> +	kfree(rproc->sync_ops);
>>>>  	kfree(rproc);
>>>>  }
>>>>  
>>>> diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
>>>> index 7dcc0a26892b..c1a293a37c78 100644
>>>> --- a/drivers/remoteproc/remoteproc_internal.h
>>>> +++ b/drivers/remoteproc/remoteproc_internal.h
>>>> @@ -27,6 +27,8 @@ struct rproc_debug_trace {
>>>>  /*
>>>>   * enum rproc_sync_states - remote processsor sync states
>>>>   *
>>>> + * @RPROC_SYNC_STATE_INIT	state to use when the remoteproc core
>>>> + *				is initialising.
>>>>   * @RPROC_SYNC_STATE_SHUTDOWN	state to use after the remoteproc core
>>>>   *				has shutdown (rproc_shutdown()) the
>>>>   *				remote processor.
>>>> @@ -39,6 +41,7 @@ struct rproc_debug_trace {
>>>>   * operation to use.
>>>>   */
>>>>  enum rproc_sync_states {
>>>> +	RPROC_SYNC_STATE_INIT,
>>>>  	RPROC_SYNC_STATE_SHUTDOWN,
>>>>  	RPROC_SYNC_STATE_CRASHED,
>>>>  };
>>>> @@ -47,6 +50,9 @@ static inline void rproc_set_sync_flag(struct rproc *rproc,
>>>>  				       enum rproc_sync_states state)
>>>>  {
>>>>  	switch (state) {
>>>> +	case RPROC_SYNC_STATE_INIT:
>>>> +		rproc->sync_with_rproc = rproc->sync_flags.on_init;
>>>> +		break;
>>>>  	case RPROC_SYNC_STATE_SHUTDOWN:
>>>>  		rproc->sync_with_rproc = rproc->sync_flags.after_stop;
>>>>  		break;
>>>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>>>> index ceb3b2bba824..a75ed92b3de6 100644
>>>> --- a/include/linux/remoteproc.h
>>>> +++ b/include/linux/remoteproc.h
>>>> @@ -619,6 +619,9 @@ struct rproc *rproc_get_by_child(struct device *dev);
>>>>  struct rproc *rproc_alloc(struct device *dev, const char *name,
>>>>  			  const struct rproc_ops *ops,
>>>>  			  const char *firmware, int len);
>>>> +int rproc_set_state_machine(struct rproc *rproc,
>>>> +			    const struct rproc_ops *sync_ops,
>>>> +			    struct rproc_sync_flags sync_flags);
>>>>  void rproc_put(struct rproc *rproc);
>>>>  int rproc_add(struct rproc *rproc);
>>>>  int rproc_del(struct rproc *rproc);
>>>>