linux-kernel - Re: [PATCH] remoteproc: stm32: fix mbox_send

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Message-ID: <e112e4a3-d5c1-caff-8ef9-cbd5b21ea3a1@foss.st.com>
Date:   Tue, 22 Jun 2021 09:56:20 +0200
From:   Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
CC:     Ohad Ben-Cohen <ohad@...ery.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH] remoteproc: stm32: fix mbox_send_message call

Hello Bjorn

On 5/28/21 10:03 AM, Arnaud POULIQUEN wrote:
> Hello Bjorn,
> 
> On 5/28/21 5:26 AM, Bjorn Andersson wrote:
>> On Tue 20 Apr 04:19 CDT 2021, Arnaud Pouliquen wrote:
>>
>>> mbox_send_message is called by passing a local dummy message or
>>> a function parameter. As the message is queued, it is dereferenced.
>>> This works because the message field is not used by the stm32 ipcc
>>> driver, but it is not clean.
>>>
>>> Fix by passing a constant string in all cases.
>>>
>>> The associated comments are removed because rproc should not have to
>>> deal with the behavior of the mailbox frame.
>>>
>>
>> Didn't we conclude that the mailbox driver doesn't actually dereference
>> the pointer being passed?
> 
> Right it can store the reference to queue the sent.
> 
>>
>> If so I would prefer that you just pass NULL, so that if you in the
>> future need to pass some actual data it will be easy to distinguish the
>> old and new case.
> 
> I can not use NULL pointer in stm32_rproc_attach and stm32_rproc_detach case.
> The reason is that the tx_done callback is not called if the message is NULL.
> (https://elixir.bootlin.com/linux/latest/source/drivers/mailbox/mailbox.c#L106)
> 
> I could use NULL pointer in stm32_rproc_kick, but I would prefer to use the same way
> of calling mbox_send_message for all use cases and not take into account the
> mailbox internal behavior.

Do you still have any concern about this patch?

Thanks,
Arnaud

> 
> Thanks,
> Arnaud
> 
> 
>>
>> Regards,
>> Bjorn
>>
>>> Reported-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
>>> ---
>>>  drivers/remoteproc/stm32_rproc.c | 14 +++++---------
>>>  1 file changed, 5 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/remoteproc/stm32_rproc.c b/drivers/remoteproc/stm32_rproc.c
>>> index 7353f9e7e7af..0e8203a432ab 100644
>>> --- a/drivers/remoteproc/stm32_rproc.c
>>> +++ b/drivers/remoteproc/stm32_rproc.c
>>> @@ -474,14 +474,12 @@ static int stm32_rproc_attach(struct rproc *rproc)
>>>  static int stm32_rproc_detach(struct rproc *rproc)
>>>  {
>>>  	struct stm32_rproc *ddata = rproc->priv;
>>> -	int err, dummy_data, idx;
>>> +	int err, idx;
>>>  
>>>  	/* Inform the remote processor of the detach */
>>>  	idx = stm32_rproc_mbox_idx(rproc, STM32_MBX_DETACH);
>>>  	if (idx >= 0 && ddata->mb[idx].chan) {
>>> -		/* A dummy data is sent to allow to block on transmit */
>>> -		err = mbox_send_message(ddata->mb[idx].chan,
>>> -					&dummy_data);
>>> +		err = mbox_send_message(ddata->mb[idx].chan, "stop");
>>>  		if (err < 0)
>>>  			dev_warn(&rproc->dev, "warning: remote FW detach without ack\n");
>>>  	}
>>> @@ -493,15 +491,13 @@ static int stm32_rproc_detach(struct rproc *rproc)
>>>  static int stm32_rproc_stop(struct rproc *rproc)
>>>  {
>>>  	struct stm32_rproc *ddata = rproc->priv;
>>> -	int err, dummy_data, idx;
>>> +	int err, idx;
>>>  
>>>  	/* request shutdown of the remote processor */
>>>  	if (rproc->state != RPROC_OFFLINE) {
>>>  		idx = stm32_rproc_mbox_idx(rproc, STM32_MBX_SHUTDOWN);
>>>  		if (idx >= 0 && ddata->mb[idx].chan) {
>>> -			/* a dummy data is sent to allow to block on transmit */
>>> -			err = mbox_send_message(ddata->mb[idx].chan,
>>> -						&dummy_data);
>>> +			err = mbox_send_message(ddata->mb[idx].chan, "detach");
>>>  			if (err < 0)
>>>  				dev_warn(&rproc->dev, "warning: remote FW shutdown without ack\n");
>>>  		}
>>> @@ -556,7 +552,7 @@ static void stm32_rproc_kick(struct rproc *rproc, int vqid)
>>>  			continue;
>>>  		if (!ddata->mb[i].chan)
>>>  			return;
>>> -		err = mbox_send_message(ddata->mb[i].chan, (void *)(long)vqid);
>>> +		err = mbox_send_message(ddata->mb[i].chan, "kick");
>>>  		if (err < 0)
>>>  			dev_err(&rproc->dev, "%s: failed (%s, err:%d)\n",
>>>  				__func__, ddata->mb[i].name, err);
>>> -- 
>>> 2.17.1
>>>