Re: [PATCH v3] i2c: imx: mark I2C adapter when hardware is powered down
From: Mukesh Savaliya
Date: Thu May 21 2026 - 07:22:03 EST
On 5/21/2026 4:21 PM, Carlos Song (OSS) wrote:
[...]
what was the reason of this hang ? I was thinking you don't have interrupts-----Original Message-----
From: Mukesh Savaliya <mukesh.savaliya@xxxxxxxxxxxxxxxx>
Sent: Thursday, May 21, 2026 3:40 PM
To: Carlos Song (OSS) <carlos.song@xxxxxxxxxxx>;
o.rempel@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx;
andi.shyti@xxxxxxxxxx; Frank Li <frank.li@xxxxxxx>;
s.hauer@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; Carlos Song
<carlos.song@xxxxxxx>; Bough Chen <haibo.chen@xxxxxxx>
Cc: linux-i2c@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx;
linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
stable@xxxxxxxxxxxxxxx
Subject: Re: [PATCH v3] i2c: imx: mark I2C adapter when hardware is
powered down
Hi Carlos,
On 5/20/2026 3:45 PM, Carlos Song (OSS) wrote:
From: Carlos Song <carlos.song@xxxxxxx>I2C transfers.
Mark the I2C adapter as suspended during system suspend to block
further transfers, and resume it on system resume. This prevents
potential hangs when the hardware is powered down but clients still
attempt
working when client requested transfer but adapter was suspended. Please
correct me if wrong.
And it would be good to mention the actual problem and why/how it occurred.
down" ?Code changes looks fine to me but have comment on commit log.
It seems, you are adding support of _noirq() callbacks to allow
transfers during suspend/resume noirq phase of PM.
Would it make sense if you can write "Replace system PM callbacks
with noirq PM callbacks" OR "Allow transfers during _noirq phase of
the PM ops" instead of "mark I2C adapter when hardware is powered
phase.
Hi,
Thank you for your comments!
But this patch is added is not for support noirq PM callback or transfer in noirq
Okay, may be actual problem description can help me.
In fact, this fix is to mark the I2C adapter as suspended duringthis time the I2C instance is powered off or the clock is disabled ... So I want to
system noirq suspend to block further transfers, and resume it on
system noirq resume. This is to prohibit I2C device calling the I2C
controller after the system noirq suspend and before noirq resume, because at
keep current commit. How do you think?
completely Makes sense. Please help add how this problem occurred and why ?
So the change/fix will be good to understand against it.
Hi,
In some I.MX platform, some I2C devices will keep a work queue all time, the work queue will
trigger I2C xfer every once in a while, but the work queue shouldn't be free in system suspend.
work queue has transfers queued even if system is suspended ? IMO, the client i2c devices should not let system go to suspend.
Within a very short time window, possibly from noirq_suspend to the system actually being suspended,
or possibly from the system starting to resume to before noirq_resume, this work queue will trigger an
I2C transfer, and at this time the I2C controller's clk and pinctrl have not yet been restored, reading and
Right, this kind of explains the problem to me. I think you are trying to serve i2c transfers when your resources(clk, pinctrl) are not turned ON and also interrupt remains disabled. And that's why you need to add _noir() PM callbacks supports along with IRQF_NO_SUSPEND | IRQF_EARLY_RESUME flags.
writing I2C registers causes the system to hang. This patch make all I2C operations are performed in a safeif my latest comments makes sense against the issue, you may write accordingly. if i am wrong, then your explanation makes sense. Cause of the hang needs to be clearly mention int the commit log in your next patch.
hardware state.
Is it better if I add these comment to patch commit log?
Carlos Song