Message-ID:
 <DM4PR12MB6109B8CCEBF5D334662E6CEE8C24A@DM4PR12MB6109.namprd12.prod.outlook.com>
Date: Wed, 30 Jul 2025 06:27:30 +0000
From: "Guntupalli, Manikanta" <manikanta.guntupalli@....com>
To: Jorge Marques <gastmaier@...il.com>
CC: David Lechner <dlechner@...libre.com>, Andy Shevchenko
	<andriy.shevchenko@...el.com>, "git (AMD-Xilinx)" <git@....com>, "Simek,
 Michal" <michal.simek@....com>, "lorenzo@...nel.org" <lorenzo@...nel.org>,
	"jic23@...nel.org" <jic23@...nel.org>, "nuno.sa@...log.com"
	<nuno.sa@...log.com>, "andy@...nel.org" <andy@...nel.org>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Pandey,
 Radhey Shyam" <radhey.shyam.pandey@....com>, "Goud, Srinivas"
	<srinivas.goud@....com>, "manion05gk@...il.com" <manion05gk@...il.com>
Subject: RE: [PATCH] iio: imu: lsm6dsx: Add shutdown callback support for I3C
 interface

[AMD Official Use Only - AMD Internal Distribution Only]

Hi,

> -----Original Message-----
> From: Jorge Marques <gastmaier@...il.com>
> Sent: Tuesday, July 29, 2025 6:19 PM
> To: Guntupalli, Manikanta <manikanta.guntupalli@....com>
> Cc: David Lechner <dlechner@...libre.com>; Andy Shevchenko
> <andriy.shevchenko@...el.com>; git (AMD-Xilinx) <git@....com>; Simek, Michal
> <michal.simek@....com>; lorenzo@...nel.org; jic23@...nel.org;
> nuno.sa@...log.com; andy@...nel.org; linux-iio@...r.kernel.org; linux-
> kernel@...r.kernel.org; Pandey, Radhey Shyam
> <radhey.shyam.pandey@....com>; Goud, Srinivas <srinivas.goud@....com>;
> manion05gk@...il.com
> Subject: Re: [PATCH] iio: imu: lsm6dsx: Add shutdown callback support for I3C
> interface
>
> On Tue, Jul 29, 2025 at 12:02:56PM +0000, Guntupalli, Manikanta wrote:
> > [AMD Official Use Only - AMD Internal Distribution Only]
> >
> > Hi @Jorge Marques,
> >
> > > -----Original Message-----
> > > From: Jorge Marques <gastmaier@...il.com>
> > > Sent: Tuesday, July 22, 2025 1:27 PM
> > > To: Guntupalli, Manikanta <manikanta.guntupalli@....com>
> > > Cc: David Lechner <dlechner@...libre.com>; Andy Shevchenko
> > > <andriy.shevchenko@...el.com>; git (AMD-Xilinx) <git@....com>;
> > > Simek, Michal <michal.simek@....com>; lorenzo@...nel.org;
> > > jic23@...nel.org; nuno.sa@...log.com; andy@...nel.org;
> > > linux-iio@...r.kernel.org; linux- kernel@...r.kernel.org; Pandey,
> > > Radhey Shyam <radhey.shyam.pandey@....com>; Goud, Srinivas
> > > <srinivas.goud@....com>; manion05gk@...il.com
> > > Subject: Re: [PATCH] iio: imu: lsm6dsx: Add shutdown callback
> > > support for I3C interface
> > >
> > > On Tue, Jul 22, 2025 at 07:32:54AM +0000, Guntupalli, Manikanta wrote:
> > > > [AMD Official Use Only - AMD Internal Distribution Only]
> > > >
> > > > Hi @David Lechner,
> > > >
> > > > > -----Original Message-----
> > > > > From: David Lechner <dlechner@...libre.com>
> > > > > Sent: Tuesday, July 22, 2025 2:31 AM
> > > > > To: Andy Shevchenko <andriy.shevchenko@...el.com>; Guntupalli,
> > > > > Manikanta <manikanta.guntupalli@....com>
> > > > > Cc: git (AMD-Xilinx) <git@....com>; Simek, Michal
> > > > > <michal.simek@....com>; lorenzo@...nel.org; jic23@...nel.org;
> > > > > nuno.sa@...log.com; andy@...nel.org; linux-iio@...r.kernel.org;
> > > > > linux-kernel@...r.kernel.org; Pandey, Radhey Shyam
> > > > > <radhey.shyam.pandey@....com>; Goud, Srinivas
> > > > > <srinivas.goud@....com>; manion05gk@...il.com
> > > > > Subject: Re: [PATCH] iio: imu: lsm6dsx: Add shutdown callback
> > > > > support for I3C interface
> > > > >
> > > > > On 7/21/25 6:38 AM, Andy Shevchenko wrote:
> > > > > > On Mon, Jul 21, 2025 at 04:37:41PM +0530, Manikanta Guntupalli wrote:
> > > > > >> Add a shutdown handler for the ST LSM6DSx I3C driver to
> > > > > >> perform a hardware reset during system shutdown. This ensures
> > > > > >> the sensor is placed in a well-defined reset state,
> > > > > >> preventing issues during subsequent reboots, such as kexec,
> > > > > >> where the device may fail to respond correctly during enumeration.
> > > > > >
> > > > > > Do you imply that tons of device drivers missing this? I don't
> > > > > > think we have even 5% of the drivers implementing the feature.
> > > > > >
> > > > > In the IIO drivers I've worked on, we always do reset in the
> > > > > probe() function. The
> > > > > shutdown() function might not run, e.g. if the board loses
> > > > > power, so it doesn't fix 100% of the cases.
> > > >
> > > > Thank you for the input.
> > > >
> > > > You're absolutely right — shutdown() may not cover all cases like power loss.
> > > However, in scenarios such as a warm reboot (kexec), the situation is different.
> > > >
> > > > Before the probe is called in the next boot, device enumeration
> > > > takes place. During
> > > this process, the I3C framework compares the device’s PID, BCR, and
> > > DCR values against the ones registered in the driver:
> > > >
> > > > static const struct i3c_device_id st_lsm6dsx_i3c_ids[] = {
> > > >         I3C_DEVICE(0x0104, 0x006C, (void *)ST_LSM6DSO_ID),
> > > >         I3C_DEVICE(0x0104, 0x006B, (void *)ST_LSM6DSR_ID),
> > > >         { }
> > > > };
> > > >
> > > > Only if this matching succeeds, the probe will be invoked.
> > > >
> > > > Since the sensor reset logic is placed inside the probe, the
> > > > device must be in a
> > > responsive state during enumeration. In the case of kexec, we
> > > observed that the sensor does not respond correctly unless it is explicitly reset
> during shutdown().
> > > Hence, adding the reset in shutdown() addresses this specific case
> > > where the probe isn't reached due to failed enumeration.
> > > >
> > > Hi Manikanta,
> > >
> > > During i3c bus init, the CCC RSTDAA is emitted to reset all DAs of
> > > all devices in the bus (drivers/i3c/master.c@..._master_bus_init ->
> > > i3c_master_rstdaa_locked). Is the LSM6DSX not compliant with that?
> > LSM6DSX is compliant with RSTDAA CCC.
> >
> > >
> > > I get your solution but find odd to use the same method as in the probe.
> > > In the probe, you would, in general, reset the device logic, but
> > > leave the i3c peripheral logic intact, because you don't want to
> > > undo whatever the controller has set-up for the current bus attached
> > > devices (ibi config, da, max devices speed, all the good i3c stuff).
> > > For this device, the st_lsm6dsx_reset_device seems to flush a FIFO,
> > > do a software reset, and reload a trimming parameter; which are
> > > necessary to solve the bug you are observed?
> > Only software reset necessary to solve the bug.
> >
> > >
> > > If possible, please explain better why the device won't enumerate
> > > correctly after a reboot without the reset. If it is a device bug,
> > > explicitly state that and that it is not compliant. Also, take a look at fig.100 of the
> i3c spec basic 1.1.1.
> > >
> > > Thank you for looking into this, this type of corner case is usually overlooked.
> > It appears that the sensor device is entering a deep sleep or low-power state and
> is not responding to CCC commands. However, after a software reset, the sensor
> starts responding to CCCs as expected.
> It should, from the silicon pov, definitely respond to CCCs, even on low-power states.
> Could you confirm with stm32 the behaviour you are observing?
> Inform them if it occurs under under i2c/i3c dual support, only i3c, or both.
> It sounds a little the messages are being filtered by the spike filter when it shouldn't?
> >
> > Shall we proceed with only the software reset changes along with an improved
> description, or do you recommend any additional modifications?
> Confirm if this is a silicon issue first, if so, a note from st should be issued also.
We are unable to verify the behavior on any silicon other than ours. It would be helpful if someone with access to a different silicon could confirm this behavior.

Thanks,
Manikanta.

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