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From:   Leo Li <leoyang.li@nxp.com>
To:     Shawn Guo <shawnguo@kernel.org>
CC:     Madalin-cristian Bucur <madalin.bucur@nxp.com>,
        Rob Herring <robh+dt@kernel.org>,
        Aisheng Dong <aisheng.dong@nxp.com>,
        Vinod Koul <vkoul@kernel.org>,
        Grant Likely <grant.likely@arm.com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        lkml <linux-kernel@vger.kernel.org>,
        "wsa@the-dreams.de" <wsa@the-dreams.de>
Subject: RE: [PATCH] arm64: defconfig: Enable FSL_EDMA driver
Thread-Topic: [PATCH] arm64: defconfig: Enable FSL_EDMA driver
Thread-Index: AQHU+TmPiTydrhJTUUimRYhw3zmrnqZjx/sAgDVIQzeAANP4cA==
Date:   Thu, 13 Jun 2019 14:01:11 +0000
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> -----Original Message-----
> From: Shawn Guo <shawnguo@kernel.org>
> Sent: Wednesday, June 12, 2019 7:45 PM
> To: Leo Li <leoyang.li@nxp.com>
> Cc: Madalin-cristian Bucur <madalin.bucur@nxp.com>; Rob Herring
> <robh+dt@kernel.org>; Aisheng Dong <aisheng.dong@nxp.com>; Vinod Koul
> <vkoul@kernel.org>; Grant Likely <grant.likely@arm.com>; moderated
> list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE <linux-arm-
> kernel@lists.infradead.org>; lkml <linux-kernel@vger.kernel.org>
> Subject: Re: [PATCH] arm64: defconfig: Enable FSL_EDMA driver
>=20
> On Wed, Jun 12, 2019 at 03:01:29PM -0500, Li Yang wrote:
> > On Thu, May 9, 2019 at 10:15 PM Shawn Guo <shawnguo@kernel.org>
> wrote:
> > >
> > > On Mon, Apr 22, 2019 at 01:30:56PM -0500, Li Yang wrote:
> > > > Enables the FSL EDMA driver by default.  This also works around an
> > > > issue that imx-i2c driver keeps deferring the probe because of the
> > > > DMA is not ready.  And currently the DMA engine framework can not
> > > > correctly tell if the DMA channels will truly become available
> > > > later (it will never be available if the DMA driver is not enabled)=
.
> > > >
> > > > This will cause indefinite messages like below:
> > > > [    3.335829] imx-i2c 2180000.i2c: can't get pinctrl, bus recovery=
 not
> supported
> > > > [    3.344455] ina2xx 0-0040: power monitor ina220 (Rshunt =3D 1000
> uOhm)
> > > > [    3.350917] lm90 0-004c: 0-004c supply vcc not found, using dumm=
y
> regulator
> > > > [    3.362089] imx-i2c 2180000.i2c: can't get pinctrl, bus recovery=
 not
> supported
> > > > [    3.370741] ina2xx 0-0040: power monitor ina220 (Rshunt =3D 1000
> uOhm)
> > > > [    3.377205] lm90 0-004c: 0-004c supply vcc not found, using dumm=
y
> regulator
> > > > [    3.388455] imx-i2c 2180000.i2c: can't get pinctrl, bus recovery=
 not
> supported
> > > > .....
> > > >
> > > > Signed-off-by: Li Yang <leoyang.li@nxp.com>
> > >
> > > Applied, thanks.
> >
> > Hi Shawn,
> >
> > Is it possible to move this patch to the -fix series so that it can
> > reach the mainline earlier?  It is having a boot failure in mainline
> > for platforms using this device without this workaround.
>=20
> Why would I2C device deferring cause boot failure on a platform?  I'm jus=
t
> trying to understand severity of the problem.

Currently the probe of imx-i2c will be retried immediately after it is defe=
rred when the optional dependency on DMA driver is not met.  This will caus=
e an indefinite loop of probe-defer-probe and keep printing the message as =
shown in the commit message.

On a further look into the imx-i2c driver, it looks like the driver need so=
me fix too.  The requesting of dma channel is done at the very late stage o=
f the imx-i2c probe after registering the i2c adapter.  Adding the i2c adap=
ter triggers the probe of the i2c bus which probably immediately triggers t=
he retry of deferred probe.  This was fine previously as requesting dma cha=
nnel didn't trigger a defer.  But now it triggers defer after commit e1ab9a=
468e3b1636d60cebd0a778461270dde208.  We probably should move the i2c_imx_dm=
a_request() to the beginning of the probe as it is considered as a dependen=
cy now.

Regards,
Leo