linux-kernel - RE: [PATCH v5 2/2] nvmem: imx-ocotp-ele: Support accessing controller for i.MX9

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Message-ID:
 <PAXPR04MB84598515572A669E5856379F88182@PAXPR04MB8459.eurprd04.prod.outlook.com>
Date: Tue, 14 Jan 2025 08:35:41 +0000
From: Peng Fan <peng.fan@....com>
To: Alexander Stein <alexander.stein@...tq-group.com>, "Peng Fan (OSS)"
	<peng.fan@....nxp.com>
CC: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>, Sascha Hauer
	<s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v5 2/2] nvmem: imx-ocotp-ele: Support accessing controller
 for i.MX9

> Subject: Re: [PATCH v5 2/2] nvmem: imx-ocotp-ele: Support accessing
> controller for i.MX9
> 
> Hi,
> 
> Am Samstag, 11. Januar 2025, 13:41:58 CET schrieb Peng Fan:
> > > Subject: Re: [PATCH v5 2/2] nvmem: imx-ocotp-ele: Support
> accessing
> > > controller for i.MX9
> > >
> > > Hi,
> > >
> > > Am Donnerstag, 9. Januar 2025, 04:34:18 CET schrieb Peng Fan:
> > > > On Wed, Jan 08, 2025 at 11:15:40AM +0100, Alexander Stein
> wrote:
> > > > >Hi Peng,
> > > > >
> > > > >Am Mittwoch, 8. Januar 2025, 08:00:18 CET schrieb Peng Fan
> (OSS):
> > > > >> From: Peng Fan <peng.fan@....com>
> > > > >>
> > > > >> i.MX9 OCOTP supports a specific peripheral or function being
> > > fused
> > > > >> which means disabled, so
> > > > >>  - Introduce ocotp_access_gates to be container of efuse gate
> > > > >> info
> > > > >>  - Iterate all nodes to check accessing permission. If not
> > > > >>    allowed to be accessed, detach the node
> > > > >>
> > > > >> Signed-off-by: Peng Fan <peng.fan@....com>
> > > > >> ---
> > > > >>  drivers/nvmem/imx-ocotp-ele.c | 172
> > > > >> +++++++++++++++++++++++++++++++++++++++++-
> > > > >>  1 file changed, 171 insertions(+), 1 deletion(-)
> > > > >>
> > > > [....]
> > > > >> +
> > > > >> +	return imx_ele_ocotp_access_control(priv);
> > > > >
> > > > >In [1] you mentioned devlink should solve the probe order. How
> > > does
> > > > >this play when the driver is compiled in (e.g. ethernet for NFS
> > > > >boot) but this OCOTP driver is just a module?
> > > >
> > > > OCOTP needs to built in for using devlink. Or the users needs to
> > > > be built as module.
> > >
> > > I don't like this kind of assumption. Would it make more sense to
> > > make CONFIG_NVMEM_IMX_OCOTP_ELE as bool instead of tristate?
> >
> > No. Users could setup their own system with this driver build in or
> > built related drivers as modules.
> 
> Sure, but if the kernel locks/fails/panics while accessing peripherals just
> because of the kernel config seems at east very unfortunate to me.
> How is someone supposed to analyze/debug this?
> 
> > At least for Android GKI, this driver needs to be as module.
> 
> Any particular reason this needs to be a module?

Android has a minimal kernel which is controlled by Google.
Vendors could only built modules based on Google's Image.

Updating this to y in upstream, means we need to change
it back to m in NXP downstream android kernel.

If you need it built in, you could modify your downstream
config, right?

Thanks,
Peng.

> Which means any affected driver needs to be a module as well just
> because if a DT reference, no? With no means to know which drivers
> are affected, despite checking for the DT references manually?
> 
> Best regards,
> Alexander
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