linux-kernel - Re: [PATCH v2 1/1] i3c: master: Avoid sending DISEC command with old device address.

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Message-ID: <ZtnJQdu2V2DPmT8R@lizhi-Precision-Tower-5810>
Date: Thu, 5 Sep 2024 11:07:45 -0400
From: Frank Li <Frank.li@....com>
To: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Cc: Ravindra Yashvant Shinde <ravindra.yashvant.shinde@....com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	"moderated list:I3C SUBSYSTEM" <linux-i3c@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>, imx@...ts.linux.dev
Subject: Re: [PATCH v2 1/1] i3c: master: Avoid sending DISEC command with old
 device address.

On Thu, Sep 05, 2024 at 03:25:09PM +0530, Mukesh Kumar Savaliya wrote:
> Hi Ravindra,
>
>
> On 8/20/2024 8:49 PM, Ravindra Yashvant Shinde wrote:
> > When a new device hotjoins, a new dynamic address is assigned.
> > i3c_master_add_i3c_dev_locked() identifies that the device was previously
> > attached to the bus and locates the olddev.
> >
> After  2-3 reads i could understand what exactly you are trying.
> Could you please keep the complete commit log here ?
>
> "
> The olddev should not receive any commands on the i3c bus as it
> does not exist and has been assigned a new address. This will
> result in NACK or timeout. So, update the olddev->ibi->enabled
> flag to false to avoid DISEC with OldAddr.
> "
>
> Make a complete story here, you don't need function to be added here since
> description should make it clear to understand.

This one is only partial fix this problem. I merged it into
https://lore.kernel.org/linux-i3c/20240829-i3c_fix-v4-1-ebcbd5efceba@nxp.com/T/#u

This one is full fix.

Frank

>
> > i3c_master_add_i3c_dev_locked()
> > {
> >      ...
> >      olddev = i3c_master_search_i3c_dev_duplicate(newdev);
> >      ...
> >      if (olddev) {
> >          enable_ibi = true;
> >          ...
> >      }
> >      i3c_dev_free_ibi_locked(olddev);
> >      ^^^^^^^^
> >      This function internally calls i3c_dev_disable_ibi_locked(addr)
> >      function causing to send DISEC command with old Address.
> >
> >      The olddev should not receive any commands on the i3c bus as it
> >      does not exist and has been assigned a new address. This will
> Isn't this the same device who raised HOTJOIN and seeking a new dynamic
> address ? you intend to have no communication with older device address
> right ?
> >      result in NACK or timeout. So, update the olddev->ibi->enabled
> >      flag to false to avoid DISEC with OldAddr.
> >      ...
> > }
> >
> > Signed-off-by: Ravindra Yashvant Shinde <ravindra.yashvant.shinde@....com>
> > ---
> > change from v1 to v2
> > - Fixed the author name.
> > - Unconditional set to the false & added some comments.
> > ---
> >   drivers/i3c/master.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> > index 7028f03c2c42..0dd8d1c28d58 100644
> > --- a/drivers/i3c/master.c
> > +++ b/drivers/i3c/master.c
> > @@ -2043,7 +2043,14 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
> >   				enable_ibi = true;
> >   				i3c_dev_disable_ibi_locked(olddev);
> >   			}
> > -
> > +			/*
> > +			 * The olddev should not receive any commands on the
> > +			 * i3c bus as it does not exist and has been assigned
> > +			 * a new address. This will result in NACK or timeout.
> > +			 * So, update the olddev->ibi->enabled flag to false
> > +			 * to avoid DISEC with OldAddr.
> > +			 */
> > +			olddev->ibi->enabled = false;
> >   			i3c_dev_free_ibi_locked(olddev);
> >   		}
> >   		mutex_unlock(&olddev->ibi_lock);