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SubjectRe: [PATCH] remoteproc: stm32: fix mbox_send_message call
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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.

Thanks,
Arnaud


>
> Regards,
> Bjorn
>
>> Reported-by: Bjorn Andersson <bjorn.andersson@linaro.org>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.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
>>

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