linux-kernel - Re: [PATCH v1 10/10] bus: mhi: core: Mark device inactive soon after host issues a shutdown

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Date:   Sun, 11 Oct 2020 05:47:49 +0530
From:   Manu Gautam <mgautam@...eaurora.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>,
        manivannan.sadhasivam@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 10/10] bus: mhi: core: Mark device inactive soon after
 host issues a shutdown


On 9/19/2020 7:32 AM, Bhaumik Bhatt wrote:
> Clients on the host may see the device in an active state for a short
> period of time after the host detects a device error or power down.

What scenario is referred as 'device error' here?
And power down is the non-graceful power_down by controller?

> Prevent any further host activity which could lead to race conditions
> or multiple callbacks to the controller or any timeouts seen by
> clients attempting to push data as they must be notified of the host
> intent sooner rather than later. This also allows the host and device
> states to be in sync with one another and prevents unnecessary host
> operations.
>
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
> ---
>  drivers/bus/mhi/core/main.c |  4 ++++
>  drivers/bus/mhi/core/pm.c   | 31 +++++++++++++++++++------------
>  2 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 1c8e332..5ec89e9 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -400,6 +400,10 @@ irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *priv)
>  
>  	 /* If device supports RDDM don't bother processing SYS error */
>  	if (mhi_cntrl->rddm_image) {
> +		/* host may be performing a device power down already */
> +		if (!mhi_is_active(mhi_cntrl))
> +			goto exit_intvec;
> +
>  		if (mhi_cntrl->ee == MHI_EE_RDDM && mhi_cntrl->ee != ee) {
>  			/* prevent clients from queueing any more packets */
>  			write_lock_irq(&mhi_cntrl->pm_lock);
> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> index 16c04ab..4e2cb41 100644
> --- a/drivers/bus/mhi/core/pm.c
> +++ b/drivers/bus/mhi/core/pm.c
> @@ -469,15 +469,10 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
>  	write_lock_irq(&mhi_cntrl->pm_lock);
>  	prev_state = mhi_cntrl->pm_state;
>  	cur_state = mhi_tryset_pm_state(mhi_cntrl, transition_state);
> -	if (cur_state == transition_state) {
> -		mhi_cntrl->ee = MHI_EE_DISABLE_TRANSITION;
> +	if (cur_state == MHI_PM_SYS_ERR_PROCESS)
>  		mhi_cntrl->dev_state = MHI_STATE_RESET;
> -	}
>  	write_unlock_irq(&mhi_cntrl->pm_lock);
>  
> -	/* Wake up threads waiting for state transition */
> -	wake_up_all(&mhi_cntrl->state_event);
> -
>  	if (cur_state != transition_state) {
>  		dev_err(dev, "Failed to transition to state: %s from: %s\n",
>  			to_mhi_pm_state_str(transition_state),
> @@ -486,6 +481,11 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
>  		return;
>  	}
>  
> +	mhi_cntrl->ee = MHI_EE_DISABLE_TRANSITION;
> +
> +	/* Wake up threads waiting for state transition */
> +	wake_up_all(&mhi_cntrl->state_event);
> +
>  	/* Trigger MHI RESET so that the device will not access host memory */
>  	if (MHI_REG_ACCESS_VALID(prev_state)) {
>  		u32 in_reset = -1;
> @@ -1051,22 +1051,29 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
>  	enum dev_st_transition next_state = DEV_ST_TRANSITION_DISABLE;
>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>  
> +	mutex_lock(&mhi_cntrl->pm_mutex);
> +	write_lock_irq(&mhi_cntrl->pm_lock);
> +
>  	/* If it's not a graceful shutdown, force MHI to linkdown state */
>  	if (!graceful) {
> -		mutex_lock(&mhi_cntrl->pm_mutex);
> -		write_lock_irq(&mhi_cntrl->pm_lock);
>  		cur_state = mhi_tryset_pm_state(mhi_cntrl,
>  						MHI_PM_LD_ERR_FATAL_DETECT);
> -		write_unlock_irq(&mhi_cntrl->pm_lock);
> -		mutex_unlock(&mhi_cntrl->pm_mutex);
> -		if (cur_state != MHI_PM_LD_ERR_FATAL_DETECT)
> +		if (cur_state != MHI_PM_LD_ERR_FATAL_DETECT) {
>  			dev_dbg(dev, "Failed to move to state: %s from: %s\n",
>  				to_mhi_pm_state_str(MHI_PM_LD_ERR_FATAL_DETECT),
>  				to_mhi_pm_state_str(mhi_cntrl->pm_state));
> -		else
> +		} else {
>  			next_state = DEV_ST_TRANSITION_FATAL;
> +			wake_up_all(&mhi_cntrl->state_event);
> +		}
>  	}
>  
> +	/* mark device inactive to avoid any further host processing */
> +	mhi_cntrl->dev_state = MHI_STATE_RESET;
> +
> +	write_unlock_irq(&mhi_cntrl->pm_lock);
> +	mutex_unlock(&mhi_cntrl->pm_mutex);
> +
>  	mhi_queue_state_transition(mhi_cntrl, next_state);
>  
>  	/* Wait for shutdown to complete */

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