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

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Date:   Tue, 22 Feb 2022 07:41:51 -0600
From:   Alex Elder <elder@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     mhi@...ts.linux.dev, quic_hemantk@...cinc.com,
        quic_bbhatt@...cinc.com, quic_jhugo@...cinc.com,
        vinod.koul@...aro.org, bjorn.andersson@...aro.org,
        dmitry.baryshkov@...aro.org, quic_vbadigan@...cinc.com,
        quic_cang@...cinc.com, quic_skananth@...cinc.com,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 13/25] bus: mhi: ep: Add support for sending events to
 the host

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@...aro.org>
>>
>> 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