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

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Date:   Tue, 13 Oct 2020 18:06:53 -0700
From:   Bhaumik Bhatt <bbhatt@...eaurora.org>
To:     Manivannan Sadhasivam <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 07/10] bus: mhi: core: Move to SYS_ERROR regardless of
 RDDM capability

On 2020-10-09 09:32, Manivannan Sadhasivam wrote:
> 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?
> 
Both client and controller drivers. I will change it to that.
>> 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
> 
I added it there because any first move to RDDM required the MHI host to 
be
inactive or in an "error" state.
However, upon further thought, I have made changes that negate this need 
and
instead make the if (mhi_cntrl->rddm_image) check dependent on the 
pm_state being
MHI_PM_SYS_ERR_DETECT.

Reason is: a first move RDDM comes after a SYS_ERROR in MHI state, since 
PM state
will already by SYS_ERROR detect by then, no client drivers or 
controllers will be able
to use the bus.
>> +			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
>> 

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
Forum,
a Linux Foundation Collaborative Project