linux-kernel - Re: [PATCH v2 8/8] bus: mhi: ep: wake up host is the MHI state is in M3

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Date:   Fri, 7 Jul 2023 16:31:35 +0530
From:   Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
CC:     <manivannan.sadhasivam@...aro.org>, <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_vbadigan@...cinc.com>,
        <quic_nitegupt@...cinc.com>, <quic_skananth@...cinc.com>,
        <quic_ramkri@...cinc.com>, <krzysztof.kozlowski@...aro.org>,
        Jeffrey Hugo <quic_jhugo@...cinc.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Dan Carpenter" <error27@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bo Liu <liubo03@...pur.com>,
        "open list:MHI BUS" <mhi@...ts.linux.dev>
Subject: Re: [PATCH v2 8/8] bus: mhi: ep: wake up host is the MHI state is in
 M3


On 7/7/2023 11:50 AM, Manivannan Sadhasivam wrote:
> On Fri, Jun 30, 2023 at 04:22:11PM +0530, Krishna chaitanya chundru wrote:
>> If the MHI state is in M3 then the most probably the host kept the
>> device in D3 hot or D3 cold, due to that endpoint transctions will not
>> be read by the host, so endpoint needs to bring the host to D0 which
>> eventually bring back the MHI state to M0.
>>
> Endpoint cannot bring the host to D0, it can only wake up the host and the host
> will bring the device to D0.
>
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
>> ---
>>   drivers/bus/mhi/ep/main.c | 16 +++++++++++++++-
>>   1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
>> index 6008818..42d3791 100644
>> --- a/drivers/bus/mhi/ep/main.c
>> +++ b/drivers/bus/mhi/ep/main.c
>> @@ -451,12 +451,14 @@ int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb)
>>   	struct mhi_ep_cntrl *mhi_cntrl = mhi_dev->mhi_cntrl;
>>   	struct mhi_ep_chan *mhi_chan = mhi_dev->dl_chan;
>>   	struct device *dev = &mhi_chan->mhi_dev->dev;
>> +	u32 buf_left, read_offset, count = 0;
>>   	struct mhi_ring_element *el;
>> -	u32 buf_left, read_offset;
>>   	struct mhi_ep_ring *ring;
>>   	enum mhi_ev_ccs code;
>> +	enum mhi_state state;
>>   	void *read_addr;
>>   	u64 write_addr;
>> +	bool mhi_reset;
>>   	size_t tr_len;
>>   	u32 tre_len;
>>   	int ret;
>> @@ -464,6 +466,18 @@ int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb)
>>   	buf_left = skb->len;
>>   	ring = &mhi_cntrl->mhi_chan[mhi_chan->chan].ring;
>>   
>> +	if (mhi_cntrl->mhi_state == MHI_STATE_M3) {
>> +		dev_dbg(dev, "wake up by ch id %x\n", mhi_chan->chan);
> This is not needed.
>
>> +		mhi_cntrl->wakeup_host(mhi_cntrl);
>> +	}
>> +
>> +	/* Wait for Host to set the M0 state */
>> +	do {
>> +		msleep(M0_WAIT_DELAY_MS);
>> +		mhi_ep_mmio_get_mhi_state(mhi_cntrl, &state, &mhi_reset);
>> +		count++;
>> +	} while (state != MHI_STATE_M0 && count < M0_WAIT_COUNT);
>> +
> Move this change to a function like mhi_ep_wake_host().
>
> - Mani

Sure I will change it in next patch.

- KC

>
>>   	mutex_lock(&mhi_chan->lock);
>>   
>>   	do {
>> -- 
>> 2.7.4
>>