linux-kernel - Re: [PATCH v4 9/9] bus: mhi: ep: wake up host if the MHI state is in M3

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Date:   Fri, 28 Jul 2023 10:04:52 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
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>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Carpenter <error27@...il.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "open list:MHI BUS" <mhi@...ts.linux.dev>
Subject: Re: [PATCH v4 9/9] bus: mhi: ep: wake up host if the MHI state is in
 M3

On Thu, Jul 13, 2023 at 12:40:18PM +0530, Krishna chaitanya chundru wrote:
> If the MHI state is in M3 then the most probably the host kept the

s/then the/then

> device in D3 hot or D3 cold, due to that endpoint transctions will not

s/transctions/transactions

> be read by the host, so endpoint wakes up host to bring the host to D0

endpoint needs to wake up the host to bring the device to D0 state...

> which eventually bring back the MHI state to M0.
> 
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/bus/mhi/ep/main.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index 6008818..46a888e 100644
> --- a/drivers/bus/mhi/ep/main.c
> +++ b/drivers/bus/mhi/ep/main.c
> @@ -25,6 +25,26 @@ static DEFINE_IDA(mhi_ep_cntrl_ida);
>  static int mhi_ep_create_device(struct mhi_ep_cntrl *mhi_cntrl, u32 ch_id);
>  static int mhi_ep_destroy_device(struct device *dev, void *data);
>  
> +static int mhi_ep_wake_host(struct mhi_ep_cntrl *mhi_cntrl)
> +{
> +	enum mhi_state state;
> +	bool mhi_reset;
> +	u32 count = 0;
> +
> +	mhi_cntrl->wakeup_host(mhi_cntrl);
> +
> +	/* Wait for Host to set the M0 state */
> +	while (count++ < M0_WAIT_COUNT) {
> +		msleep(M0_WAIT_DELAY_MS);
> +
> +		mhi_ep_mmio_get_mhi_state(mhi_cntrl, &state, &mhi_reset);
> +		if (state == MHI_STATE_M0)
> +			return 0;
> +	}
> +
> +	return -ENODEV;

ENODEV or ETIMEDOUT?

> +}
> +
>  static int mhi_ep_send_event(struct mhi_ep_cntrl *mhi_cntrl, u32 ring_idx,
>  			     struct mhi_ring_element *el, bool bei)
>  {
> @@ -464,6 +484,13 @@ 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) {
> +		if (mhi_ep_wake_host(mhi_cntrl)) {

Don't you need lock here in the case of multiple queue requests?

- Mani

> +			dev_err(dev, "Failed to wakeup host\n");
> +			return -ENODEV;
> +		}
> +	}
> +
>  	mutex_lock(&mhi_chan->lock);
>  
>  	do {
> -- 
> 2.7.4
> 

-- 
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