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Date:   Thu, 19 Oct 2023 11:39:42 -0400
From:   Frank Li <Frank.li@nxp.com>
To:     Miquel Raynal <miquel.raynal@bootlin.com>
Cc:     alexandre.belloni@bootlin.com, conor.culhane@silvaco.com,
        imx@lists.linux.dev, joe@perches.com,
        linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 Resent 6/6] i3c: master: svc: fix random hot join
 failure since timeout error
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On Thu, Oct 19, 2023 at 08:44:52AM +0200, Miquel Raynal wrote:
> Hi Frank,
> 
> Frank.Li@nxp.com wrote on Wed, 18 Oct 2023 11:59:26 -0400:
> 
> > master side report:
> >   silvaco-i3c-master 44330000.i3c-master: Error condition: MSTATUS 0x020090c7, MERRWARN 0x00100000
> > 
> > BIT 20: TIMEOUT error
> >   The module has stalled too long in a frame. This happens when:
> >   - The TX FIFO or RX FIFO is not handled and the bus is stuck in the
> > middle of a message,
> >   - No STOP was issued and between messages,
> >   - IBI manual is used and no decision was made.
> 
> I am still not convinced this should be ignored in all cases.
> 
> Case 1 is a problem because the hardware failed somehow.

But so far, no action to handle this case in current code.

In svc_i3c_master_xfer() have not check this flags. also have not enable
ERRWARN irq.

If we met this case, we can add new functions/argument to handle this.
Then we can real debug the code and recover bus.

Without this patch, simplest add some debug message before issue
SVC_I3C_MCTRL_REQUEST_AUTO_IBI, TIMEOUT will be set.

And svc_i3c_master_error() was only called by svc_i3c_master_ibi_work().
So I can think only case 3 happen in svc_i3c_master_ibi_work().

Frank

> Case 2 is fine I guess.
> Case 3 is not possible in Linux, this will not be supported.
> 
> >   The maximum stall period is 10 KHz or 100 μs.
> 
> s/10 KHz//
> 
> > 
> > This is a just warning. System irq thread schedule latency is possible
> > bigger than 100us. Just omit this waring.
> 
> This can be considered as being just a warning as the system IRQ
> latency can easily be greater than 100us.
> 
> > 
> > Fixes: dd3c52846d59 ("i3c: master: svc: Add Silvaco I3C master driver")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > ---
> > 
> > Notes:
> >     Change from v1 to v2
> >     -none
> > 
> >  drivers/i3c/master/svc-i3c-master.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> > index 1a57fdebaa26d..fedb31e0076c4 100644
> > --- a/drivers/i3c/master/svc-i3c-master.c
> > +++ b/drivers/i3c/master/svc-i3c-master.c
> > @@ -93,6 +93,7 @@
> >  #define SVC_I3C_MINTMASKED   0x098
> >  #define SVC_I3C_MERRWARN     0x09C
> >  #define   SVC_I3C_MERRWARN_NACK BIT(2)
> > +#define   SVC_I3C_MERRWARN_TIMEOUT BIT(20)
> >  #define SVC_I3C_MDMACTRL     0x0A0
> >  #define SVC_I3C_MDATACTRL    0x0AC
> >  #define   SVC_I3C_MDATACTRL_FLUSHTB BIT(0)
> > @@ -226,6 +227,11 @@ static bool svc_i3c_master_error(struct svc_i3c_master *master)
> >  	if (SVC_I3C_MSTATUS_ERRWARN(mstatus)) {
> >  		merrwarn = readl(master->regs + SVC_I3C_MERRWARN);
> >  		writel(merrwarn, master->regs + SVC_I3C_MERRWARN);
> > +
> > +		/* ignore timeout error */
> > +		if (merrwarn & SVC_I3C_MERRWARN_TIMEOUT)
> > +			return false;
> > +
> >  		dev_err(master->dev,
> >  			"Error condition: MSTATUS 0x%08x, MERRWARN 0x%08x\n",
> >  			mstatus, merrwarn);
> 
> 
> Thanks,
> Miquèl