linux-kernel - Re: [PATCH] remoteproc: k3-r5: Wait for core0 power-up before powering up core1

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Date:   Wed, 4 Oct 2023 19:21:05 +0530
From:   Apurva Nandan <a-nandan@...com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     Nishanth Menon <nm@...com>, Bjorn Andersson <andersson@...nel.org>,
        Suman Anna <s-anna@...com>, <linux-remoteproc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Devarsh Thakkar <devarsht@...com>,
        Hari Nagalla <hnagalla@...com>, Udit Kumar <u-kumar1@...com>
Subject: Re: [PATCH] remoteproc: k3-r5: Wait for core0 power-up before
 powering up core1

Hi Mathieu,

On 11/09/23 22:15, Mathieu Poirier wrote:
> Hi Apurva,
>
> On Wed, Sep 06, 2023 at 06:17:56PM +0530, Apurva Nandan wrote:
>> PSC controller has a limitation that it can only power-up the second core
>> when the first core is in ON state. Power-state for core0 should be equal
>> to or higher than core1, else the kernel is seen hanging during rproc
>> loading.
>>
>> Make the powering up of cores sequential, by waiting for the current core
>> to power-up before proceeding to the next core, with a timeout of 2sec.
>> Add a wait queue event in k3_r5_cluster_rproc_init call, that will wait
>> for the current core to be released from reset before proceeding with the
>> next core.
>>
>> Fixes: 6dedbd1d5443 ("remoteproc: k3-r5: Add a remoteproc driver for R5F subsystem")
>>
>> Signed-off-by: Apurva Nandan <a-nandan@...com>
>> ---
>>
>>   kpv report: https://gist.githubusercontent.com/apurvanandan1997/feb3b304121c265b7827be43752b7ae8/raw
>>
>>   drivers/remoteproc/ti_k3_r5_remoteproc.c | 23 +++++++++++++++++++++++
>>   1 file changed, 23 insertions(+)
>>
>> diff --git a/drivers/remoteproc/ti_k3_r5_remoteproc.c b/drivers/remoteproc/ti_k3_r5_remoteproc.c
>> index ad3415a3851b..ba5e503f7c9c 100644
>> --- a/drivers/remoteproc/ti_k3_r5_remoteproc.c
>> +++ b/drivers/remoteproc/ti_k3_r5_remoteproc.c
>> @@ -103,12 +103,14 @@ struct k3_r5_soc_data {
>>    * @dev: cached device pointer
>>    * @mode: Mode to configure the Cluster - Split or LockStep
>>    * @cores: list of R5 cores within the cluster
>> + * @core_transition: wait queue to sync core state changes
>>    * @soc_data: SoC-specific feature data for a R5FSS
>>    */
>>   struct k3_r5_cluster {
>>   	struct device *dev;
>>   	enum cluster_mode mode;
>>   	struct list_head cores;
>> +	wait_queue_head_t core_transition;
>>   	const struct k3_r5_soc_data *soc_data;
>>   };
>>   
>> @@ -128,6 +130,7 @@ struct k3_r5_cluster {
>>    * @atcm_enable: flag to control ATCM enablement
>>    * @btcm_enable: flag to control BTCM enablement
>>    * @loczrama: flag to dictate which TCM is at device address 0x0
>> + * @released_from_reset: flag to signal when core is out of reset
>>    */
>>   struct k3_r5_core {
>>   	struct list_head elem;
>> @@ -144,6 +147,7 @@ struct k3_r5_core {
>>   	u32 atcm_enable;
>>   	u32 btcm_enable;
>>   	u32 loczrama;
>> +	bool released_from_reset;
>>   };
>>   
>>   /**
>> @@ -460,6 +464,8 @@ static int k3_r5_rproc_prepare(struct rproc *rproc)
>>   			ret);
>>   		return ret;
>>   	}
>> +	core->released_from_reset = true;
>> +	wake_up_interruptible(&cluster->core_transition);
>>   
>>   	/*
>>   	 * Newer IP revisions like on J7200 SoCs support h/w auto-initialization
>> @@ -1140,6 +1146,7 @@ static int k3_r5_rproc_configure_mode(struct k3_r5_rproc *kproc)
>>   		return ret;
>>   	}
>>   
>> +	core->released_from_reset = c_state;
>>   	ret = ti_sci_proc_get_status(core->tsp, &boot_vec, &cfg, &ctrl,
>>   				     &stat);
>>   	if (ret < 0) {
>> @@ -1280,6 +1287,21 @@ static int k3_r5_cluster_rproc_init(struct platform_device *pdev)
>>   		    cluster->mode == CLUSTER_MODE_SINGLECPU ||
>>   		    cluster->mode == CLUSTER_MODE_SINGLECORE)
>>   			break;
>> +
>> +		/* R5 cores require to be powered on sequentially, core0
>> +		 * should be in higher power state than core1 in a cluster
>> +		 * So, wait for current core to power up before proceeding
>> +		 * to next core and put timeout of 2sec for each core.
>> +		 */
> Wrong multi-line comment format.
Okay will fix this.
>> +		ret = wait_event_interruptible_timeout(cluster->core_transition,
>> +						       core->released_from_reset,
>> +						       msecs_to_jiffies(2000));
>> +		if (ret <= 0) {
>> +			dev_err(dev,
>> +				"Timed out waiting for %s core to power up!\n",
>> +				rproc->name);
>> +			return ret;
>> +		}
>  From my perspective, this is needed because rproc_auto_boot_callback() for core1
> can be called before core0 due to thread execution order.  Am I correct?
Yes
> If so please add this explanation to the comment you have above.  Also, let's
> say a user decides to switch both cores off after reboot.  At that time, what
> prevents a user from switching on core1 before core0 via sysfs?
Okay, will add the explanation.
Currently, adding support for graceful shutdown is in progress. As of 
now in order
to stop/start core or change firmware, we recommend users to restart the 
OS.
> Thanks,
> Mathieu
>
>>   	}
>>   
>>   	return 0;
>> @@ -1709,6 +1731,7 @@ static int k3_r5_probe(struct platform_device *pdev)
>>   	cluster->dev = dev;
>>   	cluster->soc_data = data;
>>   	INIT_LIST_HEAD(&cluster->cores);
>> +	init_waitqueue_head(&cluster->core_transition);
>>   
>>   	ret = of_property_read_u32(np, "ti,cluster-mode", &cluster->mode);
>>   	if (ret < 0 && ret != -EINVAL) {
>> -- 
>> 2.34.1
>>