linux-kernel - RE: [PATCH v2] i2c: imx-lpi2c: change to PIO mode in system-wide suspend/resume progress

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID:
 <VI2PR04MB111472C34041D6C5E825C8CD6E8D5A@VI2PR04MB11147.eurprd04.prod.outlook.com>
Date: Fri, 21 Nov 2025 02:02:30 +0000
From: Carlos Song <carlos.song@....com>
To: Frank Li <frank.li@....com>
CC: Aisheng Dong <aisheng.dong@....com>, "andi.shyti@...nel.org"
	<andi.shyti@...nel.org>, "shawnguo@...nel.org" <shawnguo@...nel.org>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>, "kernel@...gutronix.de"
	<kernel@...gutronix.de>, "linux-i2c@...r.kernel.org"
	<linux-i2c@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] i2c: imx-lpi2c: change to PIO mode in system-wide
 suspend/resume progress



> -----Original Message-----
> From: Frank Li <frank.li@....com>
> Sent: Thursday, November 20, 2025 11:40 PM
> To: Carlos Song <carlos.song@....com>
> Cc: Aisheng Dong <aisheng.dong@....com>; andi.shyti@...nel.org;
> shawnguo@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> linux-i2c@...r.kernel.org; imx@...ts.linux.dev;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2] i2c: imx-lpi2c: change to PIO mode in system-wide
> suspend/resume progress
> 
> On Thu, Nov 20, 2025 at 06:30:39PM +0800, Carlos Song wrote:
> > EDMA resume is in early stage and suspend is in late stage, but LPI2C
> > resume and suspend are in NOIRQ stage. So LPI2C resource become ready
> > earlier than EDMA. When IRQ enabled, immediately slave will trigger
> > LPI2C to read data and the length meets the requirements for DMA
> > usage, the DMA
> 
> "the length meets the requirements for DMA usage" is condition to trigger DMA,
> reader easily miss this and confuse.
> 
> > will be needed at this time. Within a very small time window, EDMA is
> > still not resumed.
> >
> > If a system-wide suspend or resume transition is in progress. LPI2C
> > should use PIO to transfer data not DMA to avoid issue caused by not
> > ready DMA HW resource.
> 
> You can use AI help rephrase.
> 
> EDMA resume happens in the early stage and suspend in the late stage, while
> LPI2C resume and suspend run in the NOIRQ stage. This causes the LPI2C
> resources to become available earlier than EDMA. When IRQs are enabled, a
> slave device may immediately trigger LPI2C to read data. If the transfer length
> meets the DMA requirements, the driver will attempt to use EDMA even though
> EDMA may not yet be resumed.
> 
> Within this small timing window, EDMA is unavailable, leading to transfer
> failures. Force PIO mode for LPI2C during system suspend and resume
> transitions to reduce system dependency and avoid using an unready EDMA
> resource.
> 

Thank you Frank, I will send V3 according to this.

> Frank
> >
> > Fixes: a09c8b3f9047 ("i2c: imx-lpi2c: add eDMA mode support for
> > LPI2C")
> > Signed-off-by: Carlos Song <carlos.song@....com>
> > ---
> >  drivers/i2c/busses/i2c-imx-lpi2c.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > index 2a0962a0b441..d882126c1778 100644
> > --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > @@ -592,6 +592,13 @@ static bool is_use_dma(struct lpi2c_imx_struct
> *lpi2c_imx, struct i2c_msg *msg)
> >  	if (!lpi2c_imx->can_use_dma)
> >  		return false;
> >
> > +	/*
> > +	 * A system-wide suspend or resume transition is in progress. LPI2C should
> use PIO to
> > +	 * transfer data to avoid issue caused by no ready DMA HW resource.
> > +	 */
> > +	if (pm_suspend_in_progress())
> > +		return false;
> > +
> >  	/*
> >  	 * When the length of data is less than I2C_DMA_THRESHOLD,
> >  	 * cpu mode is used directly to avoid low performance.
> > --
> > 2.34.1
> >