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

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Message-ID: <2768326.mvXUDI8C0e@steina-w>
Date: Thu, 16 Jan 2025 16:47:05 +0100
From: Alexander Stein <alexander.stein@...tq-group.com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>, Peng Fan <peng.fan@....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

Hi,

Am Donnerstag, 16. Januar 2025, 03:09:02 CET schrieb Peng Fan:
> > Subject: Re: [PATCH v5 2/2] nvmem: imx-ocotp-ele: Support accessing
> > controller for i.MX9
> > 
> > Hi,
> > 
> > Am Dienstag, 14. Januar 2025, 09:35:41 CET schrieb Peng Fan:
> > > > 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.
> > 
> > Ok, that's an Android thing.
> > 
> > > If you need it built in, you could modify your downstream config,
> > > right?
> > 
> > I'm not saying I need a built-in. My concern is that a wrong Kconfig will
> > result in silent errors/lockups.
> 
> You wanna me to put this default y in arm64 defconfig in
> upstream kernel?
> 
> If yes, this could be separate patch to Shawn if this patchset got
> merged by Srinivas.

I don't know what others says about adjusting defconfig. But at least
add a comment to the Kconfig help that if built as modules, any
other driver relying on this also needs to be a module as well.

Best regards,
Alexander
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