Re: [PATCH v3 14/25] bus: mhi: ep: Add support for managing MHI state machine

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Tue, Feb 15, 2022 at 04:39:24PM -0600, Alex Elder wrote:
> On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> > Add support for managing the MHI state machine by controlling the state
> > transitions. Only the following MHI state transitions are supported:
> > 
> > 1. Ready state
> > 2. M0 state
> > 3. M3 state
> > 4. SYS_ERR state
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> 
> Minor suggestions here.		-Alex
> 
> > ---
> >   drivers/bus/mhi/ep/Makefile   |   2 +-
> >   drivers/bus/mhi/ep/internal.h |  11 +++
> >   drivers/bus/mhi/ep/main.c     |  51 ++++++++++-
> >   drivers/bus/mhi/ep/sm.c       | 168 ++++++++++++++++++++++++++++++++++
> >   include/linux/mhi_ep.h        |   6 ++
> >   5 files changed, 236 insertions(+), 2 deletions(-)
> >   create mode 100644 drivers/bus/mhi/ep/sm.c
> > 
> > diff --git a/drivers/bus/mhi/ep/Makefile b/drivers/bus/mhi/ep/Makefile
> > index 7ba0e04801eb..aad85f180b70 100644
> > --- a/drivers/bus/mhi/ep/Makefile
> > +++ b/drivers/bus/mhi/ep/Makefile
> > @@ -1,2 +1,2 @@
> >   obj-$(CONFIG_MHI_BUS_EP) += mhi_ep.o
> > -mhi_ep-y := main.o mmio.o ring.o
> > +mhi_ep-y := main.o mmio.o ring.o sm.o
> > diff --git a/drivers/bus/mhi/ep/internal.h b/drivers/bus/mhi/ep/internal.h
> > index fd63f79c6aec..e4e8f06c2898 100644
> > --- a/drivers/bus/mhi/ep/internal.h
> > +++ b/drivers/bus/mhi/ep/internal.h
> > @@ -173,6 +173,11 @@ struct mhi_ep_event {
> >   	struct mhi_ep_ring ring;
> >   };
> > +struct mhi_ep_state_transition {
> > +	struct list_head node;
> > +	enum mhi_state state;
> > +};
> > +
> >   struct mhi_ep_chan {
> >   	char *name;
> >   	struct mhi_ep_device *mhi_dev;
> > @@ -230,5 +235,11 @@ void mhi_ep_mmio_update_ner(struct mhi_ep_cntrl *mhi_cntrl);
> >   /* MHI EP core functions */
> >   int mhi_ep_send_state_change_event(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state state);
> >   int mhi_ep_send_ee_event(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_ep_execenv exec_env);
> > +bool mhi_ep_check_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state cur_mhi_state,
> > +			    enum mhi_state mhi_state);
> > +int mhi_ep_set_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state mhi_state);
> > +int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl);
> > +int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl);
> > +int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl);
> >   #endif
> > diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> > index 61f066c6286b..ccb3c2795041 100644
> > --- a/drivers/bus/mhi/ep/main.c
> > +++ b/drivers/bus/mhi/ep/main.c
> > @@ -185,6 +185,43 @@ static void mhi_ep_ring_worker(struct work_struct *work)
> >   	}
> >   }
> > +static void mhi_ep_state_worker(struct work_struct *work)
> > +{
> > +	struct mhi_ep_cntrl *mhi_cntrl = container_of(work, struct mhi_ep_cntrl, state_work);
> > +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> > +	struct mhi_ep_state_transition *itr, *tmp;
> > +	unsigned long flags;
> > +	LIST_HEAD(head);
> > +	int ret;
> > +
> > +	spin_lock_irqsave(&mhi_cntrl->list_lock, flags);
> > +	list_splice_tail_init(&mhi_cntrl->st_transition_list, &head);
> > +	spin_unlock_irqrestore(&mhi_cntrl->list_lock, flags);
> > +
> > +	list_for_each_entry_safe(itr, tmp, &head, node) {
> > +		list_del(&itr->node);
> > +		dev_dbg(dev, "Handling MHI state transition to %s\n",
> > +			 mhi_state_str(itr->state));
> > +
> > +		switch (itr->state) {
> > +		case MHI_STATE_M0:
> > +			ret = mhi_ep_set_m0_state(mhi_cntrl);
> > +			if (ret)
> > +				dev_err(dev, "Failed to transition to M0 state\n");
> > +			break;
> > +		case MHI_STATE_M3:
> > +			ret = mhi_ep_set_m3_state(mhi_cntrl);
> > +			if (ret)
> > +				dev_err(dev, "Failed to transition to M3 state\n");
> > +			break;
> > +		default:
> > +			dev_err(dev, "Invalid MHI state transition: %d\n", itr->state);
> > +			break;
> > +		}
> > +		kfree(itr);
> > +	}
> > +}
> > +
> >   static void mhi_ep_release_device(struct device *dev)
> >   {
> >   	struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
> > @@ -386,6 +423,7 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
> >   	}
> >   	INIT_WORK(&mhi_cntrl->ring_work, mhi_ep_ring_worker);
> > +	INIT_WORK(&mhi_cntrl->state_work, mhi_ep_state_worker);
> >   	mhi_cntrl->ring_wq = alloc_workqueue("mhi_ep_ring_wq", 0, 0);
> >   	if (!mhi_cntrl->ring_wq) {
> > @@ -393,8 +431,16 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
> >   		goto err_free_cmd;
> >   	}
> > +	mhi_cntrl->state_wq = alloc_workqueue("mhi_ep_state_wq", 0, 0);
> 
> Maybe it's not a big deal, but do we really need several separate
> work queues?  Would one suffice?  Could a system workqueue be used
> in some cases (such as state changes)?

Good question. The reason to have 2 separate workqueue was to avoid running the
two work items parallely during bringup. But the code has changed a lot afterwards,
so this could go into the other workqueue.

Thanks,
Mani