Re: [PATCH v1 07/10] bus: mhi: core: Move to SYS_ERROR regardless of RDDM capability

[Bhaumik Bhatt]

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@xxxxxxxxxxxxxx>
> > ---
> >  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