linux-kernel - Re: [PATCH v1 07/10] bus: mhi: core: Move to SYS

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Date:   Fri, 9 Oct 2020 22:02:31 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 07/10] bus: mhi: core: Move to SYS_ERROR regardless of
 RDDM capability

On Fri, Sep 18, 2020 at 07:02:32PM -0700, Bhaumik Bhatt wrote:
> In some cases, the entry of device to RDDM execution environment
> can occur after a significant amount of time has elapsed after the
> SYS_ERROR state change event has arrived. This can result in scenarios
> where users of the MHI bus are unaware of the error state of the

Who are all the users of MHI bus? Client drivers?

> device. Hence, moving the MHI bus to a SYS_ERROR detected state will
> prevent further client activity and wait for the RDDM entry.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
> ---
>  drivers/bus/mhi/core/main.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 2cff5dd..1c8e332 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -376,6 +376,7 @@ irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *priv)
>  	enum mhi_state state = MHI_STATE_MAX;
>  	enum mhi_pm_state pm_state = 0;
>  	enum mhi_ee_type ee = 0;
> +	bool handle_rddm = false;
>  
>  	write_lock_irq(&mhi_cntrl->pm_lock);
>  	if (!MHI_REG_ACCESS_VALID(mhi_cntrl->pm_state)) {
> @@ -400,6 +401,17 @@ 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) {
>  		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);
> +			pm_state = mhi_tryset_pm_state(mhi_cntrl,
> +						       MHI_PM_SYS_ERR_DETECT);

The condition above already moves MHI to MHI_PM_SYS_ERR_DETECT if the state
is MHI_STATE_SYS_ERR. Why are you doing it here again?

Thanks,
Mani

> +			if (pm_state == MHI_PM_SYS_ERR_DETECT)
> +				handle_rddm = true;
> +			write_unlock_irq(&mhi_cntrl->pm_lock);
> +		}
> +
> +		if (handle_rddm) {
> +			dev_err(dev, "RDDM event occurred!\n");
>  			mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_EE_RDDM);
>  			wake_up_all(&mhi_cntrl->state_event);
>  		}
> @@ -733,19 +745,15 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>  				break;
>  			case MHI_STATE_SYS_ERR:
>  			{
> -				enum mhi_pm_state new_state;
> -
> -				/* skip SYS_ERROR handling if RDDM supported */
> -				if (mhi_cntrl->ee == MHI_EE_RDDM ||
> -				    mhi_cntrl->rddm_image)
> -					break;
> +				enum mhi_pm_state state = MHI_PM_STATE_MAX;
>  
>  				dev_dbg(dev, "System error detected\n");
>  				write_lock_irq(&mhi_cntrl->pm_lock);
> -				new_state = mhi_tryset_pm_state(mhi_cntrl,
> +				if (mhi_cntrl->ee != MHI_EE_RDDM)
> +					state = mhi_tryset_pm_state(mhi_cntrl,
>  							MHI_PM_SYS_ERR_DETECT);
>  				write_unlock_irq(&mhi_cntrl->pm_lock);
> -				if (new_state == MHI_PM_SYS_ERR_DETECT)
> +				if (state == MHI_PM_SYS_ERR_DETECT)
>  					mhi_pm_sys_err_handler(mhi_cntrl);
>  				break;
>  			}
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>