linux-kernel - Re: [PATCH v2 2/2] remoteproc: stm32: add capability to detach

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Message-ID: <ad74c7d6-59d0-c522-6d2c-0608c8e9c33e@foss.st.com>
Date:   Wed, 24 Mar 2021 15:07:56 +0100
From:   Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Rob Herring <robh@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] remoteproc: stm32: add capability to detach

Hi Mathieu,

On 3/23/21 10:19 PM, Mathieu Poirier wrote:
> Good day Arnaud,
> 
> On Mon, Mar 22, 2021 at 10:26:51AM +0100, Arnaud Pouliquen wrote:
>> From: Arnaud Pouliquen <arnaud.pouliquen@...s-st.com>
>>
>> A mechanism similar to the shutdown mailbox signal is implemented to
>> detach a remote processor.
>>
>> Upon detachment, a signal is sent to the remote firmware, allowing it
>> to perform specific actions such as stopping RPMsg communication.
>>
>> The Cortex-M hold boot is also disabled to allow the remote processor
>> to restart in case of crash.
>>
>> Notice that for this feature to be supported, the remote firmware
>> resource table must be stored at the beginning of a 1kB section
>> (default size provided to the remoteproc core).
>>
>> This restriction should be lifted in the future by using a backup
>> register to store the actual size of the resource table.
> 
> I'm not sure the above two paragraphs add anything valuable to the changelog.
> At this time the size of 1kB is fixed and future enhancement are, well, in the
> future.  So for now this patch is working with the rest of the current
> environment and that is the important part.
> 
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s-st.com>
>> ---
>>  drivers/remoteproc/stm32_rproc.c | 38 ++++++++++++++++++++++++++++++--
>>  1 file changed, 36 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/remoteproc/stm32_rproc.c b/drivers/remoteproc/stm32_rproc.c
>> index 3d45f51de4d0..298ef5b19e27 100644
>> --- a/drivers/remoteproc/stm32_rproc.c
>> +++ b/drivers/remoteproc/stm32_rproc.c
>> @@ -28,7 +28,7 @@
>>  #define RELEASE_BOOT		1
>>  
>>  #define MBOX_NB_VQ		2
>> -#define MBOX_NB_MBX		3
>> +#define MBOX_NB_MBX		4
>>  
>>  #define STM32_SMC_RCC		0x82001000
>>  #define STM32_SMC_REG_WRITE	0x1
>> @@ -38,6 +38,7 @@
>>  #define STM32_MBX_VQ1		"vq1"
>>  #define STM32_MBX_VQ1_ID	1
>>  #define STM32_MBX_SHUTDOWN	"shutdown"
>> +#define STM32_MBX_DETACH	"detach"
>>  
>>  #define RSC_TBL_SIZE		1024
>>  
>> @@ -336,6 +337,15 @@ static const struct stm32_mbox stm32_rproc_mbox[MBOX_NB_MBX] = {
>>  			.tx_done = NULL,
>>  			.tx_tout = 500, /* 500 ms time out */
>>  		},
>> +	},
>> +	{
>> +		.name = STM32_MBX_DETACH,
>> +		.vq_id = -1,
>> +		.client = {
>> +			.tx_block = true,
>> +			.tx_done = NULL,
>> +			.tx_tout = 200, /* 200 ms time out to detach should be fair enough */
>> +		},
>>  	}
>>  };
>>  
>> @@ -461,6 +471,25 @@ static int stm32_rproc_attach(struct rproc *rproc)
>>  	return stm32_rproc_set_hold_boot(rproc, true);
>>  }
>>  
>> +static int stm32_rproc_detach(struct rproc *rproc)
>> +{
>> +	struct stm32_rproc *ddata = rproc->priv;
>> +	int err, dummy_data, 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);
>> +		if (err < 0)
>> +			dev_warn(&rproc->dev, "warning: remote FW detach without ack\n");
>> +	}
>> +
>> +	/* Allow remote processor to auto-reboot */
>> +	return stm32_rproc_set_hold_boot(rproc, false);
>> +}
>> +
>>  static int stm32_rproc_stop(struct rproc *rproc)
>>  {
>>  	struct stm32_rproc *ddata = rproc->priv;
>> @@ -597,7 +626,11 @@ stm32_rproc_get_loaded_rsc_table(struct rproc *rproc, size_t *table_sz)
>>  	}
>>  
>>  done:
>> -	/* Assuming the resource table fits in 1kB is fair */
>> +	/*
>> +	 * Assuming the resource table fits in 1kB is fair.
>> +	 * Notice for the detach, that this 1 kB memory area has to be reserved in the coprocessor
>> +	 * firmware for the resource table. A clean of this whole area is done on detach.
>> +	 */
> 
> Can you rework the last sentence?  I'm not sure if it means the M4 will clean
> the resource table or if that should be the application processor... I'm also
> not clear on what you mean by "clean".  Usually it means zero'ing out but in
> this case it means a re-initialisation of the original values.
This is done by the remoteproc core itself by overwriting the resource table
area with the rproc->clean_table backup.
i will rework the comment in this way.

Thanks,
Arnaud

> 
> 
>>  	*table_sz = RSC_TBL_SIZE;
>>  	return (struct resource_table *)ddata->rsc_va;
>>  }
>> @@ -607,6 +640,7 @@ static const struct rproc_ops st_rproc_ops = {
>>  	.start		= stm32_rproc_start,
>>  	.stop		= stm32_rproc_stop,
>>  	.attach		= stm32_rproc_attach,
>> +	.detach		= stm32_rproc_detach,
> 
> With the above:
> 
> Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> 
>>  	.kick		= stm32_rproc_kick,
>>  	.load		= rproc_elf_load_segments,
>>  	.parse_fw	= stm32_rproc_parse_fw,
>> -- 
>> 2.17.1
>>