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From: bbhatt@codeaurora.org
To: Loic Poulain <loic.poulain@linaro.org>
Cc: manivannan.sadhasivam@linaro.org, hemantk@codeaurora.org,
	linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] bus: mhi: Fix channel close issue on driver remove
Date: Fri, 09 Oct 2020 17:23:15 -0700	[thread overview]
Message-ID: <a86c540450437bad818b0baab4e620bc@codeaurora.org> (raw)
In-Reply-To: <1602234434-924-1-git-send-email-loic.poulain@linaro.org>

On 2020-10-09 02:07, Loic Poulain wrote:
> Some MHI device drivers need to stop the channels in their driver
> remove callback (e.g. module unloading), but the unprepare function
> is aborted because MHI core moved the channels to suspended state
> prior calling driver remove callback. This prevents the driver to
> send a proper MHI RESET CHAN command to the device. Device is then
> unaware of the stopped state of these channels.
> 
> This causes issue when driver tries to start the channels again (e.g.
> module is reloaded), since device considers channels as already
> started (inconsistent state).
> 
> Fix this by allowing channel reset when channel is suspended.
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> ---
>  drivers/bus/mhi/core/main.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index d20967a..a588eac 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1232,7 +1232,8 @@ static void __mhi_unprepare_channel(struct
> mhi_controller *mhi_cntrl,
>  	/* no more processing events for this channel */
>  	mutex_lock(&mhi_chan->mutex);
>  	write_lock_irq(&mhi_chan->lock);
> -	if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED) {
> +	if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED &&
> +	    mhi_chan->ch_state != MHI_CH_STATE_SUSPENDED) {
>  		write_unlock_irq(&mhi_chan->lock);
>  		mutex_unlock(&mhi_chan->mutex);
>  		return;
Hi Loic,

There should not be any reason for drivers to do an "unprepare" and send 
a reset channel
command during remove, as the channel context gets cleaned up after the 
remove callback
returns.

We do not want to allow moving from MHI_CH_STATE_SUSPENDED to 
MHI_CH_STATE_DISABLED state
because if a remove is called, channel context being cleaned up implies 
a reset.

Also, I have a bunch of channel state machine related patches coming up 
soon which solve
this issue and more. We are also introducing some missing features with 
that.

It would be nice if you can review/comment on those as it overhauls the 
state machine.

Let me know what you think.

Thanks,
Bhaumik
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
Forum, a Linux Foundation Collaborative Project

  reply	other threads:[~2020-10-10  0:25 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09  9:07 [PATCH] bus: mhi: Fix channel close issue on driver remove Loic Poulain
2020-10-10  0:23 ` bbhatt [this message]
2020-10-10  6:06   ` Loic Poulain
2020-10-15 17:47     ` Bhaumik Bhatt
2020-10-15 19:07       ` Bhaumik Bhatt
2020-11-06 19:41 ` Bhaumik Bhatt
2020-11-09 10:34 ` Manivannan Sadhasivam
2020-11-09 12:01 ` Manivannan Sadhasivam
2020-12-29 20:15 ` patchwork-bot+linux-arm-msm

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