Re: [PATCH v3 13/25] bus: mhi: ep: Add support for sending events to the host

[Alex Elder]

On 2/22/22 12:06 AM, Manivannan Sadhasivam wrote:
> On Tue, Feb 15, 2022 at 04:39:17PM -0600, Alex Elder wrote:
> > On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> > > Add support for sending the events to the host over MHI bus from the
> > > endpoint. Following events are supported:
> > >
> > > 1. Transfer completion event
> > > 2. Command completion event
> > > 3. State change event
> > > 4. Execution Environment (EE) change event
> > >
> > > An event is sent whenever an operation has been completed in the MHI EP
> > > device. Event is sent using the MHI event ring and additionally the host
> > > is notified using an IRQ if required.
> > >
> > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> >
> > A few things can be simplified here.
> >
> > 					-Alex
> >
> > > ---
> > >    drivers/bus/mhi/common.h      |  15 ++++
> > >    drivers/bus/mhi/ep/internal.h |   8 ++-
> > >    drivers/bus/mhi/ep/main.c     | 126 ++++++++++++++++++++++++++++++++++
> > >    include/linux/mhi_ep.h        |   8 +++
> > >    4 files changed, 155 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
> > > index 728c82928d8d..26d94ed52b34 100644
> > > --- a/drivers/bus/mhi/common.h
> > > +++ b/drivers/bus/mhi/common.h
> > > @@ -176,6 +176,21 @@
> > >    #define MHI_TRE_GET_EV_LINKSPEED(tre)			((MHI_TRE_GET_DWORD(tre, 1) >> 24) & 0xFF)
> > >    #define MHI_TRE_GET_EV_LINKWIDTH(tre)			(MHI_TRE_GET_DWORD(tre, 0) & 0xFF)
> > > +/* State change event */
> > > +#define MHI_SC_EV_PTR					0
> > > +#define MHI_SC_EV_DWORD0(state)				cpu_to_le32(state << 24)
> > > +#define MHI_SC_EV_DWORD1(type)				cpu_to_le32(type << 16)
> > > +
> > > +/* EE event */
> > > +#define MHI_EE_EV_PTR					0
> > > +#define MHI_EE_EV_DWORD0(ee)				cpu_to_le32(ee << 24)
> > > +#define MHI_EE_EV_DWORD1(type)				cpu_to_le32(type << 16)
> > > +
> > > +/* Command Completion event */
> > > +#define MHI_CC_EV_PTR(ptr)				cpu_to_le64(ptr)
> > > +#define MHI_CC_EV_DWORD0(code)				cpu_to_le32(code << 24)
> > > +#define MHI_CC_EV_DWORD1(type)				cpu_to_le32(type << 16)
> > > +
> > >    /* Transfer descriptor macros */
> > >    #define MHI_TRE_DATA_PTR(ptr)				cpu_to_le64(ptr)
> > >    #define MHI_TRE_DATA_DWORD0(len)			cpu_to_le32(len & MHI_MAX_MTU)
> > > diff --git a/drivers/bus/mhi/ep/internal.h b/drivers/bus/mhi/ep/internal.h
> > > index 48d6e9667d55..fd63f79c6aec 100644
> > > --- a/drivers/bus/mhi/ep/internal.h
> > > +++ b/drivers/bus/mhi/ep/internal.h
> > > @@ -131,8 +131,8 @@ enum mhi_ep_ring_type {
> > >    };
> > >    struct mhi_ep_ring_element {
> > > -	u64 ptr;
> > > -	u32 dword[2];
> > > +	__le64 ptr;
> > > +	__le32 dword[2];
> >
> > Yay!
> >
> > >    };
> > >    /* Ring element */
> > > @@ -227,4 +227,8 @@ void mhi_ep_mmio_get_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state *s
> > >    void mhi_ep_mmio_init(struct mhi_ep_cntrl *mhi_cntrl);
> > >    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);
> > > +
> > >    #endif
> > > diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> > > index 2c8045766292..61f066c6286b 100644
> > > --- a/drivers/bus/mhi/ep/main.c
> > > +++ b/drivers/bus/mhi/ep/main.c
>
> [...]
>
> > > +static int mhi_ep_send_completion_event(struct mhi_ep_cntrl *mhi_cntrl,
> > > +					struct mhi_ep_ring *ring, u32 len,
> > > +					enum mhi_ev_ccs code)
> > > +{
> > > +	struct mhi_ep_ring_element event = {};
> > > +	__le32 tmp;
> > > +
> > > +	event.ptr = le64_to_cpu(ring->ring_ctx->generic.rbase) +
> > > +			ring->rd_offset * sizeof(struct mhi_ep_ring_element);
> >
> > I'm not sure at the moment where this will be called.  But
> > it might be easier to pass in the transfer channel pointer
> > rather than compute its address here.

As I recall, I made this comment thinking that in the context of
the caller, the ring element address might be known; but I didn't
look at those calling locations to see.

In any case, what you do here looks correct, so that's fine.

					-Alex

> Passing the ring element to these functions won't help. Because, the ring
> element only has the address of the buffer it points to. But what we need here
> is the address of the ring element itself and that can only be found in ring
> context.
>
> Thanks,
> Mani