Re: [PATCH v4 4/4] bus: mhi: host: Take irqsave lock after TRE is generated

[Qiang Yu]

On 11/24/2023 6:09 PM, Manivannan Sadhasivam wrote:
> On Tue, Nov 14, 2023 at 01:27:41PM +0800, Qiang Yu wrote:
> > From: Hemant Kumar <quic_hemantk@xxxxxxxxxxx>
> >
> > If CONFIG_TRACE_IRQFLAGS is enabled, irq will be enabled once __local_bh_
> > enable_ip is called as part of write_unlock_bh. Hence, let's take irqsave
> "__local_bh_enable_ip" is a function name, so you should not break it.
Thanks for let me know, will note this in following patch.
> > lock after TRE is generated to avoid running write_unlock_bh when irqsave
> > lock is held.
> I still don't understand this commit message. Where is the write_unlock_bh()
> being called?
>
> - Mani
Write_unlock_bh() is invoked in mhi_gen_te()
The calling flow is like
mhi_queue
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)
    mhi_gen_tre
        write_lock_bh(&mhi_chan->lock)
        write_unlock_bh(&mhi_chan->lock)   // Will enable irq if 
CONFIG_TRACE_IRQFLAGS is enabled
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)

after adding this patch, the calling flow becomes

mhi_queue
    mhi_gen_tre
        write_lock_bh(&mhi_chan->lock)
        write_unlock_bh(&mhi_chan->lock)
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)
> > Signed-off-by: Hemant Kumar <quic_hemantk@xxxxxxxxxxx>
> > Signed-off-by: Lazarus Motha <quic_lmotha@xxxxxxxxxxx>
> > Signed-off-by: Qiang Yu <quic_qianyu@xxxxxxxxxxx>
> > ---
> >   drivers/bus/mhi/host/main.c | 13 +++++--------
> >   1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
> > index 33f27e2..d7abd0b 100644
> > --- a/drivers/bus/mhi/host/main.c
> > +++ b/drivers/bus/mhi/host/main.c
> > @@ -1128,17 +1128,15 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
> >   	if (unlikely(MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)))
> >   		return -EIO;
> >   
> > -	read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
> > -
> >   	ret = mhi_is_ring_full(mhi_cntrl, tre_ring);
> > -	if (unlikely(ret)) {
> > -		ret = -EAGAIN;
> > -		goto exit_unlock;
> > -	}
> > +	if (unlikely(ret))
> > +		return -EAGAIN;
> >   
> >   	ret = mhi_gen_tre(mhi_cntrl, mhi_chan, buf_info, mflags);
> >   	if (unlikely(ret))
> > -		goto exit_unlock;
> > +		return ret;
> > +
> > +	read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
> >   
> >   	/* Packet is queued, take a usage ref to exit M3 if necessary
> >   	 * for host->device buffer, balanced put is done on buffer completion
> > @@ -1158,7 +1156,6 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
> >   	if (dir == DMA_FROM_DEVICE)
> >   		mhi_cntrl->runtime_put(mhi_cntrl);
> >   
> > -exit_unlock:
> >   	read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
> >   
> >   	return ret;
> > --
> > 2.7.4