linux-kernel - Re: [PATCH 1/4] remoteproc: Introduce always-on flag

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Message-ID: <57A30E84.9010109@st.com>
Date:	Thu, 4 Aug 2016 11:44:36 +0200
From:	loic pallardy <loic.pallardy@...com>
To:	Bjorn Andersson <bjorn.andersson@...aro.org>
CC:	<linux-remoteproc@...r.kernel.org>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	<linux-kernel@...r.kernel.org>, Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH 1/4] remoteproc: Introduce always-on flag



On 08/04/2016 12:02 AM, Bjorn Andersson wrote:
> On Tue 02 Aug 08:17 PDT 2016, loic pallardy wrote:
>
>> Hi Bjorn,
>>
>> On 08/01/2016 08:58 PM, Bjorn Andersson wrote:
>>> Introduce an "always-on" flag on rprocs to make it possible to flag
>>> remote processors without vdevs to automatically boot once the firmware
>>> is found.
>>>
>> Should this flag rather be named "auto-boot"? From my pov, "always-on" means
>> coprocessor can't be shutdown.
>>
>
> I saw it from the view of the remoteproc driver, in which case it's
> always-on. But I'm fine with naming it "auto-boot" instead.
>
> [..]
>>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> [..]
>>> @@ -978,11 +982,16 @@ static int rproc_add_virtio_devices(struct rproc *rproc)
>>>   int rproc_trigger_recovery(struct rproc *rproc)
>>>   {
>>>   	struct rproc_vdev *rvdev, *rvtmp;
>>> +	int ret;
>>>
>>>   	dev_err(&rproc->dev, "recovering %s\n", rproc->name);
>>>
>>>   	init_completion(&rproc->crash_comp);
>>>
>>> +	/* shut down the remote */
>>> +	/* TODO: make sure this works with rproc->power > 1 */
>>> +	rproc_shutdown(rproc);
>>> +
>>>   	/* clean up remote vdev entries */
>>>   	list_for_each_entry_safe(rvdev, rvtmp, &rproc->rvdevs, node)
>>>   		rproc_remove_virtio_dev(rvdev);
>>> @@ -993,7 +1002,17 @@ int rproc_trigger_recovery(struct rproc *rproc)
>>>   	/* Free the copy of the resource table */
>>>   	kfree(rproc->cached_table);
>>>
>>> -	return rproc_add_virtio_devices(rproc);
>>> +	ret = rproc_add_virtio_devices(rproc);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	/*
>>> +	 * boot the remote processor up again, waiting for the async fw load to
>>> +	 * finish
>>> +	 */
>>> +	rproc_boot(rproc);
>> You are changing current behavior by forcing rproc boot whatever
>> "always-on". Moreover coprocessor already rebooted by
>> rproc_add_virtio_device if "always-on" flag is set, doesn't it?
>> If yes, rproc->power will be equal to 2 and rproc_shutdown call will failed
>> as this second rproc_boot call is unknown from customer pov.
>>
>
> rproc_add_virtio_devices() does no longer call rproc_boot(), this patch
> moves that call. So for always-on rprocs "power" will go 1 -> 0 -> 1 in
> this function.
>
> What does change is that for a non-always-on case.
>
> If we have 1 client that has requested rproc_boot() then the current
> implementation will bring "power" down to 1 and we will wait until the
> client for some reason calls rproc_shutdown(). After that we might boot
> the system again, if there are any vdevs in the resource table.
>
> Here we will bring "power" from 1 -> 0 -> 1, without regarding who's
> holding references.

I'm fine with the final sequence in which only rproc_shutdown and 
rproc_boot are called (with patch 3 modifications).

But having a look only to this patch, we have the following function call:

rproc_trigger_recovery
   |__ rproc_shutdown --> power from 1 -> 0
   |__ rproc_add_virtio_devices
	|__ rproc_fw_config_virtio
		|__ (if always_on == 1) rproc_boot_nowait --> power from 0 --> 1
   |__ rproc_boot
	if always_on == 1 power from 1 --> 2
	else power from 0 --> 1

on this patch rproc_boot should be called only is always_on flag is not set.

With patch 3, call to rproc_add_virtio_devices is suppressed and 
behavior is ok.

Regards,
Loic
>
>>> +
>>> +	return 0;
>>>   }
>
> Regards,
> Bjorn
>