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

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Message-ID: <ZP9ELdOQ9WMj2Rxd@p14s>
Date:   Mon, 11 Sep 2023 10:45:33 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Apurva Nandan <a-nandan@...com>
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 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.

> +		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?  

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?

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
>