linux-kernel - Re: [PATCH 3/4] nvmem: imx-ocotp: Support accessing controller for i.MX8M Nano

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Message-ID: <Z6OVKqy+bRLNa4GY@lizhi-Precision-Tower-5810>
Date: Wed, 5 Feb 2025 11:43:22 -0500
From: Frank Li <Frank.li@....com>
To: Alexander Stein <alexander.stein@...tq-group.com>
Cc: 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>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	devicetree@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] nvmem: imx-ocotp: Support accessing controller for
 i.MX8M Nano

On Wed, Feb 05, 2025 at 07:51:23AM +0100, Alexander Stein wrote:
> Am Freitag, 31. Januar 2025, 17:06:23 CET schrieb Frank Li:
> > On Fri, Jan 31, 2025 at 02:54:06PM +0100, Alexander Stein wrote:
> > > Hi,
> > >
> > > Am Donnerstag, 30. Januar 2025, 17:42:32 CET schrieb Frank Li:
> > > > On Thu, Jan 30, 2025 at 02:01:00PM +0100, Alexander Stein wrote:
> > > > > i.MX8M OCOTP supports a specific peripheral or function being fused
> > > > > which means disabled, so
> > > > >  - Introduce disable_fuse for a list of possible fused peripherals.
> > > > >  - Iterate all nodes to check accessing permission. If not
> > > > >    allowed to be accessed, detach the node
> > > > >
> > > > > Signed-off-by: Alexander Stein <alexander.stein@...tq-group.com>
> > > > > ---
> > > > >  drivers/nvmem/Kconfig     |   3 ++
> > > > >  drivers/nvmem/imx-ocotp.c | 105 +++++++++++++++++++++++++++++++++++++-
> > > > >  2 files changed, 107 insertions(+), 1 deletion(-)
> > > > >
...
> > > multiples fuses for disables. This is an excerpt from imx8mp WIP
> > > > struct disable_fuse imx8mp_disable_fuse[] = {
> > > > 	[IMX8MP_OCOTP_CAN_DISABLE]		= { .fuse_addr = 16, .mask = BIT(28) },
> > > > 	[IMX8MP_OCOTP_CAN_FD_DISABLE]		= { .fuse_addr = 16, .mask = BIT(29) },
> > > > 	[IMX8MP_OCOTP_VPU_VC8000E_DISABLE]	= { .fuse_addr = 16, .mask = BIT(30) },
> > > > 	[IMX8MP_OCOTP_IMG_ISP1_DISABLE]		= { .fuse_addr = 20, .mask = BIT(0) },
> > > > 	[IMX8MP_OCOTP_IMG_ISP2_DISABLE]		= { .fuse_addr = 20, .mask = BIT(1) },
> > > > 	[IMX8MP_OCOTP_IMG_DEWARP_DISABLE]	= { .fuse_addr = 20, .mask = BIT(2) },
> > > > };
> > >
> > > Notice the fuse_addr of 16 and 20.
> >
> > Yes, I am not sure if it good idea to encode fuse_addr to IMX8MP_OCOTP_CAN_DISABLE
> >
> > like
> >
> > #define IMX8MP_OCOTP_CAN_DISABLE  16 << 16 | BIT(28)
> >
> > So dt-bindings/nvmem/fsl,imx8mn-ocotp.h can be moved to dts directory.
>
> Mh, I personally don't like encoding offsets into bits. How about using
> > '#access-controller-cells = <2>'
> and using the defines like this
> > #define IMX8MP_OCOTP_CAN_DISABLE  16 0x10000000

I think it is good. better told peng fan to align this!

Frank

>
> DT stays the same:
> > access-controllers = <&ocotp IMX8MP_OCOTP_CAN_DISABLE>;
>
> Note: It seems BIT(x) is not usable in DT.
>
> Best regards,
> Alexander
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