Re: [PATCH v2 1/5] bus: mhi: core: Handle syserr during power_up

[Bhaumik Vasav Bhatt]

Hi Jeff,

We will always have the mhi_intvec_handler registered and trigger your 
wake_up state event when you write MHI RESET. BHI INTVEC IRQ using 
mhi_cntrl->irq[0] is _not_ unregistered once you enter AMSS EE.

So, your below assumption is not true:
>>>So, if we are in the PBL EE, we would expect to see the BHI 
interrupt, but if we are in the AMSS EE, we would expect to see a MHI 
interrupt.

At the start of mhi_async_power_up(), you've already registered for the 
BHI interrupt as we do setup for IRQ and it is only unregistered from 
power down if power up on the same cycle was a success.

On 4/10/20 8:03 AM, Jeffrey Hugo wrote:
> On 4/9/2020 6:55 PM, Hemant Kumar wrote:
> > On 4/7/20 9:50 AM, Jeffrey Hugo wrote:
> > > The MHI device may be in the syserr state when we attempt to init it in
> > > power_up(). Since we have no local state, the handling is simple -
> > > reset the device and wait for it to transition out of the reset state.
> > >
> > > Signed-off-by: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
> > > ---
> > > Â drivers/bus/mhi/core/pm.c | 20 ++++++++++++++++++++
> > > Â 1 file changed, 20 insertions(+)
> > >
> > > diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> > > index 52690cb..3285c9e 100644
> > > --- a/drivers/bus/mhi/core/pm.c
> > > +++ b/drivers/bus/mhi/core/pm.c
> > > @@ -9,6 +9,7 @@
> > > Â #include <linux/dma-direction.h>
> > > Â #include <linux/dma-mapping.h>
> > > Â #include <linux/interrupt.h>
> > > +#include <linux/iopoll.h>
> > > Â #include <linux/list.h>
> > > Â #include <linux/mhi.h>
> > > Â #include <linux/module.h>
> > > @@ -760,6 +761,7 @@ static void mhi_deassert_dev_wake(struct 
> > > mhi_controller *mhi_cntrl,
> > > Â int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
> > > Â {
> > > +ÂÂÂ enum mhi_state state;
> > > ÂÂÂÂÂ enum mhi_ee_type current_ee;
> > > ÂÂÂÂÂ enum dev_st_transition next_state;
> > > ÂÂÂÂÂ struct device *dev = &mhi_cntrl->mhi_dev->dev;
> > > @@ -829,6 +831,24 @@ int mhi_async_power_up(struct mhi_controller 
> > > *mhi_cntrl)
> > > ÂÂÂÂÂÂÂÂÂ goto error_bhi_offset;
> > > ÂÂÂÂÂ }
> > > +ÂÂÂ state = mhi_get_mhi_state(mhi_cntrl);
> > > +ÂÂÂ if (state == MHI_STATE_SYS_ERR) {
> > > +ÂÂÂÂÂÂÂ mhi_set_mhi_state(mhi_cntrl, MHI_STATE_RESET);
> > > +ÂÂÂÂÂÂÂ ret = readl_poll_timeout(mhi_cntrl->regs + MHICTRL, val,
> > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ !(val & MHICTRL_RESET_MASK), 1000,
> > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mhi_cntrl->timeout_ms * 1000);
> > can we use this instead of polling because MSI is configures and 
> > int_vec handler is registered
> >
> > ÂÂÂÂ wait_event_timeout(mhi_cntrl->state_event,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ MHI_PM_IN_FATAL_STATE(mhi_cntrl->pm_state) ||
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mhi_read_reg_field(mhi_cntrl, base, MHICTRL,
> > ÂÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂÂÂ MHICTRL_RESET_MASK,
> > ÂÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂÂÂ MHICTRL_RESET_SHIFT, &reset) || !reset ,
> > ÂÂÂÂ ÂÂÂ ÂÂÂ ÂÂ msecs_to_jiffies(mhi_cntrl->timeout_ms));
> >
> > 1) In case of MHI_PM_IN_FATAL_STATE we would not be accessing MHI reg
> > 2) Consistent with current MHI driver code.
>
> I'm not sure this works in the way you intend.
>
> state_event is linked to the intvec, which is the BHI interrupt. I 
> don't see that the state_event is triggered in the MHI interrupt path 
> (mhi_irq_handler). So, if we are in the PBL EE, we would expect to 
> see the BHI interrupt, but if we are in the AMSS EE, we would expect 
> to see a MHI interrupt.
>
> Now, for my concerned usecase, those two interrupts happen to be the 
> same interrupt, so both will get triggered, but I don't expect that to 
> be the same for all usecases.
>
> So, with the solution I propose, we exit the wait (poll loop) as soon 
> as we see the register change values.
>
> With the solution you propose, if we only get the MHI interrupt, we'll 
> have to wait out the entire timeout value, and then check the 
> register. In this scenario, we are almost guaranteed to wait for 
> longer than necessary.
>
> Did I miss something?
>
> > > +ÂÂÂÂÂÂÂ if (ret) {
> > > +ÂÂÂÂÂÂÂÂÂÂÂ dev_info(dev, "Failed to reset MHI due to syserr 
> > > state\n");
> > > +ÂÂÂÂÂÂÂÂÂÂÂ goto error_bhi_offset;
> > > +ÂÂÂÂÂÂÂ }
> > > +
> > > +ÂÂÂÂÂÂÂ /*
> > > +ÂÂÂÂÂÂÂÂ * device cleares INTVEC as part of RESET processing,
> > > +ÂÂÂÂÂÂÂÂ * re-program it
> > > +ÂÂÂÂÂÂÂÂ */
> > > +ÂÂÂÂÂÂÂ mhi_write_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_INTVEC, 0);
> > > +ÂÂÂ }
> > > +
> > > ÂÂÂÂÂ /* Transition to next state */
> > > ÂÂÂÂÂ next_state = MHI_IN_PBL(current_ee) ?
> > > ÂÂÂÂÂÂÂÂÂ DEV_ST_TRANSITION_PBL : DEV_ST_TRANSITION_READY;
--
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