Re: [PATCH v6 5/5] bus: mhi: ep: wake up host if the MHI state is in M3

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Jul 10, 2024 at 04:46:12PM +0530, Krishna chaitanya chundru wrote:
> If the MHI state is in M3 then most probably the host kept the
> device in D3 hot or D3 cold, due to that endpoint transactions will not
> reach the host, endpoint needs to wakes up the host to bring the host
> to D0 which eventually bring back the MHI state to M0.

s/needs to wakes up/needs to wake up/

s/D3 hot/D3hot/
s/D3 cold/D3cold/
to match other uses and make grep more effective.

> while queueing packets if the MHI state is in M3 wakeup host to bring
> back link to M0.

s/while/While/
s/MHI state is in M3/MHI is in M3/ (twice)

> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> ---
>  drivers/bus/mhi/ep/main.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index b3eafcf2a2c5..b8713e5c1e1a 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);

Tangent: the "M0_WAIT_DELAY_MS" name suggests that is the maximum
delay, but it seems the actual maximum delay is
M0_WAIT_DELAY_MS * M0_WAIT_COUNT.

Tangent 2: unless there's a reason to be different, it would be nice
to use the same loop structure as the similar delay in mhi_ep_enable().

> +		mhi_ep_mmio_get_mhi_state(mhi_cntrl, &state, &mhi_reset);
> +		if (state == MHI_STATE_M0)
> +			return 0;
> +	}
> +
> +	return -ENODEV;
> +}